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MG MGB GT V8 Factory Originals Technical - Turbo V8?

I am doing a V8 conversion in my MG hopefully using a built up 4.6L Rover motor with a single plane intake and the Holley Commander 700 CFM EFI Kit. I am going to have something lke 8.5:1 CR Pistons put into the thing so I can run a turbo or two:). Anyone seen or heard of anything like this. I could get manifolds made up no prob and run one or two small quick spooling turbos and plumb for an intercooler. Anyone think this could be possible. Im only running an alternator no ac or anything like that so I have a little bit more room. Good idea or an engineering nightmare? I think it could be done if I can find some small body turbos and run maybe 7 lbs. boost each. Wouldnt that be great, as if a 4.6L in a B wasnt enough power already, turn the boost up and run down anything. Who knows; maybe a dream but if my friend can do it on his 5.0 Poonstang, I sure as hell can try. Turbos might take a bit more work but theyre ten times better than any supercharger ever will be. Just a thought.
Jarrod Hills

Jarrod, why do you say turbochargers are better? Myself, I prefer blowers for sure. Better bottom end.

A lot of people think that but it really isnt true. Why would you want to use an induction system that eats power to make power? If you properly size your turbo, you can get it to start making power the same place that a supercharger makes and it will continue to make boost after the blower has stopped. The other thing is since the blower is being driven off the front of the motor whats going to wear out more quickly; the bearings. Did you know that the average NHRA drag car gives up 600 to 800 horsepower just to drive the blower? Thats why turbos are better. You use waste energy to make energy instead of using energy to make energy. The only downfall is they create more heat but thats easily delt with. Just my opinion.
Jarrod Hills

At the risk of exposing my ignorance of the subject for all the world to see, I gotta jump in on this one.

Jarrod wrote:

"Did you know that the average NHRA drag car gives up 600 to 800 horsepower just to drive the blower?"
The typical NHRA dragster makes around 7,000 - 8,000HP. 600 - 800 is a small price to pay for that.

"Thats why turbos are better."
If Turbos are better, why would NHRA dragsters use a blower? Why wouldn't they use a turbo instead?

"You use waste energy to make energy instead of using energy to make energy."
This is a common misconception, but it simply isn't true. It takes energy to put the exhaust gas out the exhaust pipes. The more restrictions in the exhaust path, the more power it takes. It takes energy to spin the turbo, energy that has to come from the engine. You don't get something for nothing. Turbos may be more efficient (or not, I don't know), but they certainly don't operate for free.

I personally don't know the trade offs between blowers and turbos, but what little I do know suggests to me that blowers are better for the street, and turbos are better for the race track (not the drag strip, but high speed road or track racing).

BTW, just for the record, a turbo is a supercharger, but a supercharger is not necessarily a turbo. By definition, supercharging is the act of forcing air into an engine by some external means. It can be by a mechanical blower or compressor, or it can be by air ducting forcing air into the engine when the vehicle is moving at a high speed. Turbocharger is the term for a specific type of supercharger, one that is driven off the exhaust gas. Over the years, "blower" has come to mean a supercharger that is driven mechanically off the engine. There are typically two types of superchargers: centrifical and positive displacement. Centrifigal superchargers are more or less like a ventilation fan; the amount of air moved per revolution varies depending on the back pressure. Positive displacement superchargers, on the other hand, pump a fixed amount of air per revolution. Because of these differences, a centrifugal supercharger can handle a back fire, but a positive displacement type will explode if it doesn't have a relief valve. Most cars on the street, especially those that are supercharged at he factory, use centrifugal blowers (with the exception of street rodders, where appearance is the most important thing. It's hard to beat the image of a GMC blower sticking out of the hood).

At least that's what I think - I could be wrong. I certainly have been before.

This promises to be an interesting and enlightening thread, I look forward to the comments.
Dan Masters

The NHRA doesn't use turbo's because they banned them
Michael Hartwig

Michael wrote:

"The NHRA doesn't use turbo's because they banned them."

Thanks for the info. What was the reason they were banned?
Dan Masters

As always, "It Varies". If you like turbos, go ahead, but they're not cheap, they're not easy, the power isn't free, and they are not necessarily better than a blower. However I would dearly love to see a good dual turbo installation. Beyond that you're talking apples and oranges because there's no really suitable way to match one against the other. You'll have a great deal of trouble with the exhaust heat so plan for the worst and resolve that issue before you even consider starting. Also, there is no intrinsic advantage I am aware of in a dual turbo arrangement. Instead of 8 cylinders driving 1 turbo you have half that many cylinders driving each turbo. The same old problem of fast spool-up vs choking off the top end is still there. Plus there's more surface area for heat transfer in the wrong direction for the given volume.

As for the supposed shortcomings of the blower, things have progressed a bit there as well, you know. Modern bearings are easily superior to the sleeve bearings still used on V8 crankshafts, bypass valves reduce parasitic losses at cruise to insignificant levels while still giving instant boost on demand, and so on and so forth. You've seen the websites, you know the arguments. You've clearly made your choice, but don't expect it to be mindlessly validated by those of us here who have run both types of superchargers. That ain't happening. (Ten times better? You have a gift for exaggeration my boy.)

As for practical answers, for a turbo 7lbs will be woefully inadequate and require no intercooling whatsoever. You could run 10:1 compression and maybe even use the cheap gas. No, for what you want to do maybe you'd better shoot for the 14-24lb range. That would be roughly equivalent to running 7 to 14lbs with a blower. Since the 4.6 has FI anyway there'd be no good reason to scrap it in favor of old technology (TBI), plus it'll give you the ignition control you need.

But perhaps most importantly, can you afford to pay somebody to build this car for you? Not to be critical, but I get the impression you might be biting off a bit much unless you have an accomplished helper.

Um... am I being overly critical here? Sorry, just my present mood I guess.

Jim Blackwood

the theory of multiple turbos is as you said quicker spool up times. The for d302/351 guys use dual turbos out of Thunderbird super coupes. They get large amounts of power out of these things. Info is out there, but yes the heat of a turbo is a major negative in our already hot cars.
Larry Embrey

I don't know about the 4.6, but I know there are tons of "kits" out there for a 5.0 Ford. Where are you going to get your headers? Regular exhaust tubing will crack in no time, you need something really heavy duty. I am making the turbo header for my 2.3Ford out of 1.5 inch weld els. Go to the plumbing supply house to get them and have some flanges made up. I have even seen where people just flip the exhaust manifolds upside down on a 5.0 and mount the turbos there.

The reason people run 2 small turbos instead of 1 larger is packaging. One turbo will always be more efficient...only one turbo shaft spinning instead of two. If you go for two, Larry hit the nail on the head. Look for a couple of T3's off an 83-86 TurboCoupe/XR4Ti/SVO. Shoot for .63 hot side, as .48 will spool up too quick and run out of steam a little earlier. Good luck packaging it all up.

You may also have diffuculty with intercooler location. I am looking at cutting the frame behind the bumper to fit my Volvo unit in my MG. It will support about 300 rwhp, but I wouldn't expect higher from it. I have heard good things about a Starion intercooler, and it fits better but are harder to find. Even these are realistically limited to about 350 rwhp. For a new intercooler, expect to drop about $1,000 for the setup, and then you will have to fabricate it all up.

You also will need a really good engine management system. Right now on there is a group buy on a TEC III for $1500. It would be a good choice for the price. Then, all you will need is an intake and big throttle body...and sensors.

All in all, yes it can be done. I would choose turbos instead of blower because you are in a light car that doesn't need low end. If you don't have plenty of torque coming out of the hole with any V-8...choked by a turbo or not, you need a better engine. Oh, yea, must have FORGED exceptions unless you like rebuilding engines.

Oh well, I think that will get the thoughts moving. I love turbos. I have an XR4 and a TurboCoupe 2.3 going in my MG. Set up well, they are great. They really got a bad rap from the 60's to 80's when they weren't fuel injected. Now days, they are reliable and are really only notice they are there when you need them.

G.P. Copes

The NHRA banned turbos because they made too much power and beginning to become unsafe. A turbo DOES use waste energy to drive its compressor. To think likewise is wrong. A supercharger does use energy to drive it. Why is it that when people put underdrive pulleys on the front of their motor, they make power? You take some resistance off of the motor by allowing ancilliaries to spin slower. Why would you add something that adds so much more resistance and wear to the motor? If lowering resistance adds power, wouldnt adding resistance....take power? Oh no, could I be right in my takes power to make power statement? Maybe. A turbo is driven off wasted energy created by the burnt gas.

Since I wrote the first thread, Ive had the opportunity to talk to my friend with the Turbo'd 5.0 that runs a TE72 Turbo and have decided to go with a TE44 sized turbo running around 14 lbs.

As for having someone else build the car up for me, Ive been working on cars since I was 10. Ive done everything from simple ignition system work to building motors (5 so far. B four banger, 350 Big Block Pontiac, 400 ram air 4 pontiac, 302 Ford). I think I can handle this. And I am not looking for "midless validation" from anyone. If it came off as such, perhaps your "mood" twisted it into such a way, as no one else seems to have come away with such an impression. Comparing a Turbo with a supercharger is not comparing apples and oranges. They are methods of forced induction, therfore apples and apples or oranges and oranges, whichever floats your boat. Have you really ever taken a look at any of the Vortech (possibly the Best centrifigul superchargers out there) superchargers? Well gosh, if they just arent the compressor side of a turbo with a gearbox on the drive side for the belt so that the impeller can spin fast enough to make boost. Thats like saying you cant compare a Ford motor with a Mopar motor because they dont look exactly the same and are painted different colors from the factory. Theyre still motors and they still use gas and they still move cars.

I will not be using the Rover EFI system because it will require me to find all the pieces to do so since I will be either building the motor myself or having it built for me, not just going out into a Landie wrecking yard and pulling a used motor for my car. I am thinking about using the TBI system because it comes with everything, including an ECU that is easily programmed for my application. Yes, it isnt the newest technology but it is easily put together and will work superbly.

In a 2000 lbs car with 250+ horsepower and 250+ lb ft torque, who needs something thats going to make getting off the line any harder than it already is? If you get a turbo to kick in midrange that way the motor will still be making peak plus some horsepower, I think thats the ticket.

Am I lashing out...umm...maybe or perhaps its the mood Im in. Or maybe its because I really dont know anything about cars and survive off of "accomplished helpers." HAHA that might be the way it goes for some but definately not for me.

This all started becasue I wanted to know if anyone had turbo'd their 8. I guess not. Oh well. Please forgive my rant but I cant stand it when some one makes condescending remarks about me when they have no idea who or what I can do. Again, sorry. Thanks.
Jarrod Hills


I hope you didn't take any of my comments as being condensending, because they certainly weren't meant that way. You asked an interesting question, made some interesting comments, and I thought I would participate in the discussion.

I'm sure there are differences in the efficiencies of the two types of supercharging, turbo vs blower, and it's not unreasonable that the turbo might be the most efficient, but I still disagree that a turbo uses waste energy to operate. If it didn't take energy to drive the turbo, we could easily solve one of the most difficult problems in doing a V8 swap, and that's the exhaust system. It takes power from the engine to pump the spent gas out of the engine; The more restrictive the exhaust system, the more energy it takes. Otherwise, we could just use 1/4 inch tubing for our exhaust headers, and route the exhaust anyway we wanted too.

You're right, the compressor portion of a turbo and a Vortech blower are similar, therefore it takes a similar amount of energy to compress the same amount of air with either one. One gets its energy from a belt or gear drive, and the other from the exhaust gas, but it takes the same energy into the compressor vanes either way. It takes EXACTLY the same amount of energy to compress a given amount of air at a given temperature in a given time to a given boost, regardless of the method chosen to do it. What varies is how much energy "IN" is required to provide the necessary energy "OUT". Turbos may take less, but they still take energy nevertheless. To do otherwise would be a violation of the laws of physics.

There are two factors at work in getting the exhaust out of the engine - the natural expansion of the spent gas, and the pressure from the rising pistons. If you restrict the exhaust, the pistons have to work harder to expel the gas, and the expanding gas spends more of its energy fighting the rise of the piston. Both of these factors reduce the power output of the engine. If you are going to draw enough energy to drive a turbo charger, you will place a restriction on the exhaust. The higher your boost, the more restrictive the exhaust becomes.

Personally, I'm of the opinion that a blower is the prefered choice for street use, but as I said before, I am by no means an expert, and I hope to be educated by this discussion. I did a fairly detailed study of this subject many years ago, but all that I remember now is my conclusion - the details have been lost to time. I don't have the time, tools, or the talent to build a turbo system myself to test my opinion, so I'm happy that you are doing it. When you're finished, I would hope to get a chance to see it. Whether the end result produces more, less, or the same power, it's still a worthwhile exercise. If you patent your design and get rich from it, that's fine: if it's a total failure and you have to scrap it and start over again, that's fine too. The end result is not as important as the doing.

Good luck and best wishes.
Dan Masters

Jarrod, my younger son name is Jared. Anyway Turbos, yes they make power and yes it takes a short while to get to the rear wheels due to lag. You have to make exhaust before you spin the compressor. Have you ever driven a twin turbo? I have. I do not care for them. It requires lots of tuning to get the right fuel mixture, and yes-lower compression about 7 to 1 with 9 or more lb of pressure. You will find lots of holes in the tuning process with turbos.
Haltec processors may be your ticket for MPI or TBI.
Free hp? I once try to get the flywheel to act as a blower (with small vanes) Pressurizing the bell housing and routing that air to the carb, I would imaging that would be free hp. A blower fills all the tuning holes, therefore it's easier to tune, and the fact is that blowers do not have lag. The must recent car that I drove with twin turbos is a right hand drive Subaru race car twin turbo from Japan, that puts out 475 hp (I was told) and it felt like it, it also takes a different style of driving, braking and acceleration timing is critical. It was work to drive the car on the track; all that hp was not enjoyable.
My vote goes for blowers, simple, instant, easy to adjust output (change pulley), and they are good for lots of trouble free miles.
I also drove a Miata with a Jackson Racing blower kit simple and power was instant, a real pleasure to drive on the track and on the street. This Miata had a new Mazda 1.6 engine with a blower that had over 150k miles
The blower was on his second engine. Lots of torque right now, not later.
If you think turbos are the tickect, do it. It would be interesting to see a MGB V8 with twin turbos.

Bill Guzman

Turbochargers are better for outright power than superchargers in a road car. A single turbo install is not more efficient than a twin turbo. A twin turbo installation is usually a lot better, more so for a Big V type engine or similar, partly as it is easier to fit, but also it is easier to spool up 2 small turbos than one big one. Therefore less lag. With todays modern ball bearing turbos, it would be quite easy to build an engine, with little or no lag, and still make very good power.
For those who say they have driven a twin turbo V8, and didnt like it, that has very little relevance. Perhaps, and it must have been, it was a very bad turbo installation. To compare a twin turbo subaru, which is an unusual car, also has no relevance. A 2.0 ltr car with twin turbos isnt really necessary, as there are plenty of single turbochargers capable of producng 475bhp. And to say it wasnt fun???? I dont think so. They are pretty amazing cars.
As for setting up a twin turbo...any performance engine will be tricky to set up. Turbochargers make no difference. 7:1 CR should be easily good for 15+psi with good intercooling. Possibly even 20psi.
I have built a few rover v8 twin turbo engines, and can only say good things about them. Sure I ahve had my problems along the way, but it does work. They do make power, and lag for all there has been on mine, isnt a problem. Also, forged pistons are not necessary. A good quality high silicon ( hyperteutectic ) piston will work very well in a turbo engine. Forced induction does not break pistons. Detonation or weak mixtures will, but a good quality piston will last a long time in a road car. I am currently using the standard 4.6 low compression pistons, which are of very good design and quality.
For an out and out race engine, forged pistons would be better, but for the street, they would be nice, but not essential.
I made my manifolds using weld els as you call them, but there are cast manifolds available for building a turbo motor, but it depends on how much room you have whether they would suit.
My current engine is a 4.6 twin turbo, with a DTA FAST P8Pro management system. A pair of Garret T3's, and 2 big intercoolers. I am only using 12psi at the minute, as I am having a few teething problems. but they will soon be sorted once I can get a few dry days to test the car.
My last 3.9 engine was also twin turbo, but blowing through a holley, and it performed very very well, although it was a little hard on fuel.
Jarrod, if you like, you can email me, and I will send pics.


Guess I hit a nerve. I'd apologize Jarrod, but really now, what do you expect? Aren't you at all familiar with thermodynamics and energy conversion theory? As said above that energy to squeeze the intake charge has to come from someplace. True, some of it is derived from the heat of the exhaust gasses, but by no means all of it, and in fact the only place for the turbo to get power from is the combustion process itself. Choking off the exhaust with a turbine changes the efficiency and timing of that process, which now has to be optimized for the production of exhaust gasses in a manner best suited to spin the turbine, which in turn compromises free breathing at high speed. Then there's the heat introduced by compression and also turbulence and pumping losses (not to mention reversion losses) especially as velocities reach critical speeds and resistance to flow begins to climb exponentially. And there's the whole issue of compressor stall to consider. Not a primary consideration maybe, but worth looking at. If you ever spent much time looking at operational charts for turbos the only thing that is quite clear is that there simply is no ideal turbo for any given application.

You wanted to hear from someone who has put a turbo BOP/R in an MGB? Well you have. The Olds Jetfire was a turbo package, and a fairly decent one. I put that engine in my '71 as my next to last engine swap (V-8 engine combination #4) using custom heavywall headers, a 2" SU carby with ultra low restriction air filter, and a low compression rating. It would put out 7psi of boost and ran reasonably well, but the lag is a real irritation where handling is concerned. It more than once put me sideways when I could least afford it, and was the direct cause of two collisions. (And I'm a fairly accomplished back country road racer mind you) That right there is my major complaint with a turbo. Plus, as mentioned above, the tuning curve is an absolute horror. Incidentally, In case you aren't aware of the operational distinction between a Paxton and a Roots type blower, The Paxton doesn't boost at low speed like the Roots does. Maybe you would like that better from what you said, but I find that extra torque down low to be something I like. I guess I am as qualified as anybody on this forum to compare the turbo and blower installations as my last was the former and my current is the latter, and I still say apples and oranges.

Jim Blackwood

Jim, you are so right about handling. One-hour spring race on a twin turbo Subaru was lots of work that was not fun at all. Perhaps on the street it would be ok but then what can you do with it, stop sign racing.
Any performance add ons will work for the person doing the project. For me the roots blower does the trick. Bolt it on and go, no teething problems.
Now, why put on twin turbos on a street car? What is the logic behind that exercise, just asking, and not been a critic.
Bill Guzman

Personally, I'd rather be blown............
DTR Ross

Yep, I too prefer to be blown.., getting a turbo feeling in my spine..
ZZ to top

Ok, here goes. The turbofords I work on are 8:1 compression and regularly run about #20 boost...give or take a couple with a T3 or T3/T4 hybrid. Hell, they were pumping #15 stock. I can give you dozens of pictures of exactly how well hypercrackin pistons hold up under those conditions. If you play with turbos enough, it isn't if you get some detonation, but when. Never be cheap when building a short block, do it right the first time and never worry about it again.

As for packaging, I am running a 3 inch downpipe and exhaust on my 2.3. For a V8 single turbo, you need to run your 2 3-4 inch exhausts into one turbo, then a 5 inch out the back, or a splitter to run twin exhaust. Then you have to mount it. Most of the junkyard turbo V8 builders out there just flip exhaust manifolds and mount 2 T3s for simplicity, then duel 3 inch exhaust. Good enough for consistant 10 second passes most of the time.

I do agree with turbos being difficult on a road coarse. Blowers definitely shine in the smooth delivery of power.


P.S. I am a dihard Pontiac buff. I have owned more owned and built more Pontiacs than I can just about remember. Pontiac never made a bigblock. They made a small journal 326-400(leaving out the really early years) and large journal 421-455.

G.P. Copes

Just my $.02 but I prefer the "Blower in a bottle" route. Just chug along using a V8's 200-300 HP putting no strain on anything, but when necessary just hit that button for BIG grins. Yes it too has drawbacks, my number one complaint is running out of the giggle gas which won't happen with a turbo or SC. Also the all or nothing mode that it runs in, can cause real concern in road racing environment (but not so much in dragstrip type runs) but can be minimized by dual staging. If set up correctly it has no more negative effects than a SC or turbo.
Michael S. Domanowski

Why put twin turbos on a street motor???? To get power by any chance???
On a subaru, it is very unusual to run twin turbos, so It is a little odd that someone has chose to do this, especially on such a small engine, so no mater what way it is done, a small engine producing bigh HP will have lag, that is just a simple fact. They may have tried a sequential system, with a small turbo and big turbo, with a valve seperating the 2 turbos. The small turbo supposed to spool up quickly, with the second bigger turbo taking over at higher rpm's. In theroy a good approach, but most good single turbos also work very well. Toyota Supra twin Turbos also use the sequential system, small/big turbo.
Twin turbos on a V, will be easier to install in most cases, spool up quicker, and also have the ability to produce silly amounts of power. I have no knowledge of the turbo engine you installed in your MGB, but it sounds like a very old suck through system using an SU. Very very old stuff. Ive never driven anything as old as that, but I imagine I wouldnt be impressed by it either. Suck through, with no intercooler??? No thanks.
I admit, that I have never driven a supercharged car, basically because they are very rare over here. The price of such an installation means no 1 really does them. I would like to try one of the new turbo style superchargers, but until they come down in price, I will continue with turbos. In my opinion they are the easiest and cheapest way to get power.
As for turbos restricting/choking the exhaust gas flow. The benefits from a turbo far outwiegh any restriction they cause. In fact on some high power setups, inlet manifold pressure will be higher than exhaust manifold pressure, so while tere me be a restriction of sorts, all the air is still wanting to go in the right direction. Even on a small turbo setup, exhaust manifold pressure shouldnt really be any more than 10psi above inlet pressure, which is nothing to worry about at all.
Another good thing about a turbo, is that it does not use huge amounts of power to drive it, as in a supercharger installation.
Some people favour each. I do prefer turbos at the minute, perhaps If I can afford a Supercharger or 2 someday, I may change my mind, but until that happens.
Dont knock a good turbo install, as they are very hard to beat. And dont compare to any old outdated systems you may have driven either.
How many factory supercharged motors are there??? Not anywhere near as many as turbocharged. Ever consider why???

Stevie wrote:

"As for turbos restricting/choking the exhaust gas flow. The benefits from a turbo far outwiegh any restriction they cause."

There is no dispute whatever about that, but the same thing can be said of superchargers. In one of the examples mentioned earlier, 800 hp was used to drive a supercharger, in return for 7 -8,000hp. Not a bad trade off. BTW, someone said one of the reasons that NHRA banned turbos was becuase they produced excessive power. That may be, but I am highly doubtful that was a reason. A few years ago, these engines were producing "only" 5,000HP. If power restriction was a concern, why wouldn't other steps have been taken to limit power before they got to the 7-8,000HP range?

"Another good thing about a turbo, is that it does not use huge amounts of power to drive it, as in a supercharger installation."

I guess I have to question this statement also. Without the impeller blades, it takes a miniscule amount of power to spin a blower. Why does a blower impeller take so much more power to provide the same boost as the impeller on a turbo? I'm sure there are differing efficiences related to each type, and one will be better than another for a given application, but I can't buy the orders of magnitude being ascribed to the relative efficiencies. Phrases like "huge amounts" and "10 times" leave me a bit cold.

"How many factory supercharged motors are there??? Not anywhere near as many as turbocharged. Ever consider why???"

Yes, I have considered this, along with why did most makers go to McPherson struts, front wheel drive, and a lot of other not so good ideas. Absolutely the last thing in the world I would consider as a good reason for something is that the manufacturers are using it. Another thing along that line I have also noticed, is that more makers are going to superchargers, and fewer are using turbos. There is also a vastly increased choice of "bolt-on supercharger kits for after market use, surpassing the number of "bolt-on" turbocharger kits available.

I have a feeling that when the dust settles on this discussion, we'll not have an "A is better than B" conclusion, but that A works better for some aplications, and B works beter for others. The real question is which best suits the application to an MGB with a V8, for use on the street.

I have my opinion, but it is what we used to call an "unjustified assumption" back when I was doing engineering calculations for nuclear power plants. It could be used for preliminary anaylsis, but it had to be justified before the calc could be issued for use. I don't plan on using either one, but I'm curious nevertheless. If I were, I'd be doing a lot more research before making a decision.

If you go all the way back to WWII, you'll find that some planes used superchargers, and some used turbochargers. Guess they couldn't decide either :)

An interesting side note: a few years ago, someone built a Chevy Nova with two turbo chargers AND two blowers. It ran, but as it was a show car, no one knows how well it could have ran. Or how poorly!
Dan Masters

<<An interesting side note: a few years ago, someone built a Chevy Nova with two turbo chargers AND two blowers. >>

Hey Dan,

I remember that car! It wasn't a Nova, though (although the guy that built it had an award winning Nova, too).

It was a GM "J" series car. In fact, I think it was a Pontiac J something, maybe J2000? I still have the mag somewhere in one of many magazine boxes.

Okay. Did some 'net research.

His name is Rick Dobbertin. He built a Chevy II Nova that had 2 turbos feeding a 6-71 roots blower on a 454. The Pontiac J2000 he built next had 2 turbos & 2 smaller blowers. He also built this outrageous amphibian Surface Orbiter.


I believe you're right - my memory ain't what it used to be. The guy's name was Dobbins or similar? The guy put an ungodly amount of work into that car. Every weld on the car was ground smooth and polished, for example. There was a lot of animosity towards him for a while, because he raised the bar so high for show cars that others didn't think they could compete. He actually got physical threats against his life!

That was what, 20 years ago?
Dan Masters

To answer all the "ney sayers" about superchargers, I currently own two supercharged cars.
A 2001 Jaguar XKR (4.0L V8, 370 HP and nearly 700 lbs heavier then the C5 )as fast(er) as the C5 Corvette (5.7L) I previously owned.
A 2002 Mini Cooper S (1.6L, 165 HP) and the most fun you can have legally on the road.
Both of these cars are fabulous, I just enjoy them for what they.
Tony Bates

Just got back. Anyway, yes the Jetfire was an old design. Still it was pretty advanced back in '62 when it came out, sort of like some of the big tube twin turbos today would be, but that wasn't the point. If it's nothing but raw power we're after here for the least money, I still say buy one of those all aluminum SBC's and then add whatever aftermarket stuff you want. A simple, well trodden path to power.

But I don't think that was the question. Perhaps Jarrod should define his objective more specifically, 'cause that may be getting lost in the discussion. Is a BOP/R or 4.6L the only engine of choice? Is he equally open to alternative forced induction systems? etc. I think turbos are great if you don't have to time the power coming out of a curve or drive on slippery surfaces, but so is nitrous. And having a delay between the time you hit the pedal and the time the power hits the wheels can be disastrous under those conditions. As can anything other than the most exquisite control over just how much power. These are sports cars after all, and some people think a sports car should be fun to drive through the twisties. For me, the blower is well suited for that. As for which makes the most power, I doubt any but the very best drivers and mechanics could determine that, but for most of us, even though we (sometimes not so secretly) think that we are the best, we'll do ourselves a real big favor by building what is for us the most fun to drive. And I gotta tell you guys, that Eaton has a major grin factor built right in.

Jim Blackwood

Very, VERY well put! That is something a number of "old school" car guys have mentioned. One bieing that modifying strickly looking at what the top #'s are can be dangerous, and two being that unless you are a pro, you will be hard pressed to tell difference or be able to utilize the extra power effectively.

I could very easy (money permitting) build my 302 to be 500-600hp, different cam, full porting on heads and intake, forged pistons, a vortec blower putting out around 8psi. But why? With what I already have I will be lucky to get it al to the road due to the chassis limited ability to put the power down.
Larry Embrey

No, a BOPR V8 isnt my only choice. In fact, I am looking at the possibility of a 60 degree Chevy V6 with twins on it. Advantages come in the form of a lot more room to do a turbo set up. After looking at the B some more, it would be great to do a turbo 8 but, there really isnt that much room under the bonnet to do so, hence my looking into V6's. Ive already found a guy whose done it (motors in a 510 though) and looking for some info from him. Besides, an American 6 cylinder built up for turbo use costs half as much as a BOPR motor does. I have heard of using both a turbo and a supercharger and if I remember correctly, the Army has a heavy truck with both. In theory it seems like a good idea. Supercharger for low revs and when the supercharger runs out of boost (higher revs), the turbo kicks in.

Mil spec truck you refer to is a two cycle GM engine that has a blower 3-71, 4-71 to 8-71 etc. there is also a 3-53 so on, first digit signifies the number of cylinders, 71 is the displacement per cylinder.
The turbo is a natural addition to increase the torque at higher revs on these engines and so on, no lag on these engines, but there is lag on the Cummings, and Cat which it ahs been reduce with electronic trothle control etc.

I want to make one thing clear, I am not advertising or selling ok!
At present I am working on a blower for the 60-degree V6 that is about 11/2 inches taller than a TBI.
This roots blower with a 4.3 TBI and computer chip modify develops about 40 to 45% increase in power in a stock 2.8 with 1.77:1 pulley ratio it all depends on assembly etc. With ported heads about 45 to 55%
The blower runs wet, meaning that the TBI is on top of the blower thus the mixture in flowing through the vanes of the blower and compresing both, Oxigen and fuel.
This blower was installed in the 87-90 S-10's at the dealership with GM warranty. At present I am working on pulley design to use one serpentine belt in the MG
A turbo would develop too much heat in the small engine bay and the exhaust would be a very expensive item to make for the B. I have talk to Turbo City to adapt a turbo to a V6 on a MGB; I decided to go with the Blower on my personal project car.
As for the Subaru twin turbo, this is common in Japan, let me tell you, this car is a rocket ship and makes good use of the 13-inch rotors and 6 piston calipers which are a must. Power on small car has to match to the chassis of the car. When I ask why twin turbo's? I was asking why so much power on a B, would it be a useful power output on the B? Or is it just for looks. One of the best factories blower vehicle I have seen is the Ford Lighting, it makes a good use of the blower power to suspension, it is great, and power to weight is border line but outperforms a Chevy truck with larger engines.

Bill Guzman

Then Jarrod, perhaps the next relevant question would be, how exactly are you planning on using this vehicle? Please be as specific as you can, is it a hot rod, show car, daily driver? What sort of weather will it see, what sort of roads and driving. Turbos may very well be your best bet, I wouldn't know at this point. If you're building a stoplight sleeper it could be just the ticket. OTOH, maybe someone here can make a helpful suggestion that hasn't been raised yet.

Jim Blackwood

If you are thinking of going V6 turbo, you can get a set dirt cheap off many Chrysler products. Most are T25s and everytime I hit the jy I see at least 5 or 6 of them. Not worth my time to pull off, but for a twin V6, they would probably be just the ticket. Of course, if you are going to go with a larger V6, like a 4.3 GM, then I would consider twin T3s with a .48 hot side for a quick spool. I also agree with Jim, for the twisties, supercharger is the way to go. I was going for a stoplight terror, so felt turbo (4 cylinder)was my way to go. If the lag gets too bad, there is always the little blue bottle to spray the lag away.

Just another thought...I saw a turbo Probe today with an intercooler that you may be able to use. A little small, but should be room in the MG. Run one intercooler per turbo, then join before the throttle body. Call me cheap, I like searching the jys to find most of my parts.

G.P. Copes

another seemingly always overlooked powerplant is the Rotary Mazda, they are EXTREMELY small and very strong for thier size. Late model RX7's came with TT from the factory. In a RX7 I have heard of them running in 13's and the RX7 is heavier.

Thier small size makes them great for MG's in fact you could amost store luggage in the engine bay with one!!

They love to wind out which suits fast backroad driving very well, and with turbos or a blower the power would be absolutely awesome.
Larry Embrey

For anyone doubting what I said in my previous post on this subject please go to: This is the proof you all need!
Michael S. Domanowski

Just to spice things up a bit:

Popular Hot Rodding, January, 2003:

1) 406ci, twin turbo pontiac Catalina. 1200HP on alcohol, 3200 pounds, and 8.58/160 1/4 mile times.

2) 4.6L twin turbo Ford Mod motor in a Mustang. 622 rear wheel HP. 9.78/140 1/4 mile times

Super Rod, December, 2002:

1) 811HP 383 small block Chevy, with a Vortec blower


Turbochargers, by Hugh Macinnes, HP Books, ISBN 0-912656-49-2

Super Power: A Do It Yourself Guide to Turbochargers, Superchargers, Fuel Injection, and Nitrous oxide, SA Design, ISBN 0-931472-02-4
Dan Masters

Here are a couple of links for a little SVO mustang owned by one Jon Dell Blair. One is of just him going down the strip, the other he is racing a blown Vette. Not bad for a little turbo 4...with a little money thrown at it.

Just a little fuel for the fire!

G.P. Copes

With all this talk about making super power in an MG, what plans do you have of strengthening the frame? I have a hopped up 305 chev in mine and to date im afraid to shift it hard and twist anything. Just curious about what people have done, or whether or not the mg frame could possibly handle 300+ horsepower reliably.

Alan Raddatz

Which all proves there's no success like excess.
Jim Blackwood

Seems my post was just a trifle out of sequence, sorry 'bout that. Do you think you could direct us to some shots of your conversion? It's not that often we get to see a MGB/SBC conversion and I know there are several who would like to look at it including yours truely. How did you handle the steering and exhaust, was that difficult?

As to your question, one of the more common methods used to strengthen the unibody for higher horsepower (Sorry Dan, Torque ;) is to form up a member to connect the front spring perch to the sill reinforcing member at the jack point. Several websites have info on this modification. Aside from that, the body itself was built surprisingly strong, and to date no one has reported any torque induced damage that can be verified. Closest so far are Larry's ripples in the left inner fender which may be a factory oddity.

Jim Blackwood

Jim, yes you are correct, it could be a factory oddity. It is very smooth ripples, and no creasing. I just don;t remember it being there before. Then agin I have a unfortunately large header hole due to a change in header design after I started cutting, which should get reinforced.
Larry Embrey

Alan, just answering you with your own asnwer.
In another placae Alan said:
"Everybody is always talking about suspension/handling characteristics of a modified car. You're all kidding yourselves, half of you baby the hell out of the cars to the point where anything over 50 hp is worthless anyway, and any of you who actually autocross or drive the car hard have tuned the suspension to much better than factory. Anyone who pretends that they need the full suspension and handling capacity of the stock MGB is just kidding themselves. Get the car, replace a few things, it'll be a sweet rod. If you're looking for a car that handles well, get a civic, or a crown vic, or a greyhound. Any of them would at least match an mg."

Good enough for him should be good enough for you Alan.

"another seemingly always overlooked powerplant is the Rotary Mazda, they are EXTREMELY small and very strong for thier size. Late model RX7's came with TT from the factory. In a RX7 I have heard of them running in 13's and the RX7 is heavier."

Well they can do better than that. Here is one example of a friend of mine in his RX-7. Not too bad.

..........REACTIVE RACING...........
...........10.73 @ 128mph...........
1.50 60' on ET. Streets
SR Motorsports Stage 2 KKK single turbo

BTW - I can run 13's all day in my non-turbo rotory powered midget, imagin if I boosted it another 100hp....

I'd like to see a Buick Grand National motor in a B :o)
Brian Kraus

I guess I should just scroll down to the Grand National post....
Brian Kraus


i appreciate the attempt at showing me up, but it seems that you really havent answered my question at all. Im not worried about suspension, my car holds itself fine for the type of driving i want to do, im not looking to fly around in autocrosses or anything. What im worried about is the car handling 320 horsepower without twisting any of the frame or body panels. Last time i checked this wasnt really a suspension issue at all. Jim, unfortunately i have no pictures posted anywhere at this time, except for the exterior of the car back in the 4 cyl days (its on this website). Hopefully i will get some pics taken over the christmas break when i finally get some time (im a cs student in university). The exhaust fit inside the engine compartment.

Alan Raddatz

Perhaps you would be good enough to share some of the challenges of that conversion with us. What did you find difficult or problematical? Is this a garden variety SBC? Any trouble with the distributor, carb, or heater, starter, clutch, radiator, etc? Is it stock or otherwise in appearance? Were you able to weigh the engine before it went in?
Jim Blackwood

Wow, thats quite a loaded question. The engine itself has a realtively high lift cam, the heads have been worked over a little, and apart from that, just the usual edelbrock intake and 600cfm carb. To get the engine in nice and deep and set back, the heater was completely removed, the footwells narrowed a little bit, the crossmember cut down and rebuilt, and the steering redone, needs to be redone again! The rad is 4 core, and goes from the stock top of the mg rad to the bottom of the crossmember, its huge! The car doesnt look stock anymore, i put a 351 mustang scoop on the hood, which in my opinion makes the car look more agressive, and sets it apart a little. No clutch problems as it is a turbo 350 trans, and the started fits no prob, and is from a 4.3 v6 truck. Didnt weight the engine, it wouldnt have made a difference for me anyway, sorry.

Although we did keep the exhaust in the engine bay, with the stock cast iron manifolds i might add, i think that were i to do it again, i would route the exhaust through the inner fenders in order to cool the engine bay better. Also, im gonna have to louvre the hood as the big engine just doenst let air flow through the massive rad. I havent changed the rear yet, but have coped with that problem with a very low stall converter, and thus the engine wont punch right of the bat, and instead needs to be guided up from 800 to about 2000 before the car goes nuts and the tires start smoking. Let me know about any other questions.

Alan Raddatz

Sorry to backtrack, but I caught the debate a little late.
Traditionally, superchargers were the best option for quick response street use. Yes the sequential set-up narrative was correct. I've actually run a twincharge system which consisted of a supercharger to turbo set-up which handed things off to the turbo around 4 grand. The problem as with sequential turbos is a jolt as the larger turbo comes on line. You must either run sequentially (jolt) or continue running both chargers (no by-pass). Doesn't work to well. Either the supercharger which is geared for low-end response is over-sped or the smaller turbo goes beyond it's efficiency range and creates too much heat (detonation). With todays turbo tech. (ceramic or ball bearing) lag isn't a factor. It is critical however, that the turbo is properly sized. Yes, turbos do have a negative effect (added backpressure). Where n/a enginges require some backpressure for torgue, a turbo itself provides virtually all the backpressure you need. With an extremely free-flowing exhuast a turbo is nearly free hp. A turbo is also very easy to adjust (bleeder valve / dial-a-boost) which costs about $15. With a V-8, I would run two small (quick spooling) turbos of the same size and with the same boost. With two turbos sharing the load, you'll be able to run higher combined boost (efficiency range) without intercooling. If you intercool, you'll have enough power capability to tie a 'B' and most other cars into a knot.
Im currently building a Ford 2.3T 'B'. Easy 280-300 hp with about 280 ft/lb and never need to go over 5500 rpm. This is an incredibly cheap package with a mated T-5.

Sorry to run on.
Rob Rich

This thread was discussed between 06/11/2002 and 30/11/2002

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