Welcome to our resource for MG Car Information.



MG parts spares and accessories are available for MG T Series (TA, MG TB, MG TC, MG TD, MG TF), Magnette, MGA, Twin cam, MGB, MGBGT, MGC, MGC GT, MG Midget, Sprite and other MG models from British car spares company LBCarCo.

MG MGB GT V8 Factory Originals Technical - Buick 3.8L

Alright I've been looking for info on converting my stock mgb's engine(blown for the 4th time) to a buick 3.8L V6 from a buick Grand national. Since the 3.8l is roughly the same as the buick 215 V8, and produces more HP overall (300HP stock) then that particular V8 does, I was wondering if anyone has done this kind of conversion before, and if so where I could get info on it at? Yes I have looked through the archives, and no there's nothing on this particular motor conversion, unlike the GM 60degree motors which are more compact in size and easier to fit then this 90 degree motor is. If anyone has an info I'd be highly appreciative to get it.

I was also wondering if anyone knew which trans would work best for it? I'm wanting an auto tranny but having no idea of the comparable sizes of trans is somewhat making that notion a headache. I'd like a trans roughly the same size as a ford T-5 but if one isn't found I'll have to stick with the ford trans for the time being.

Also if anyone knows if this engine conversion has been done before. I wouldn't suppose anyone would happen to know if the engine/tranny brackets for such a conversion is up for sale or not. I have little qualms about cutting into the mg's engine bay, as long as it doesn't mean going the route a friend of mine did and routing the exhuast on the outside of the car there by ruining its stock appearance.

So basically I'm looking for engine conversion info, bracket info, and tranny info.

I already have a V8 rear end, and can build the rest of the parts easily enough myself (driveshaft, and whatnot).
CJD Dark

A friend of mine had a GN. IIRC the Buick GN was turboed to get to 300hp. The installation filled up the compartment under the hood considerably. Do you think it will fit? Somewhat peaky, it could not outpull a Porsche 928.

Also one quirk that my friend had with his GN was the complex and troublesome hydraulic pump needed to provide pressure for the brake system booster as vacuum was not available.

I don't recall it being a derivative of the 215.

If you find a reasonable GN donar car, it would be worth restoring rather than gutting.
Edd Weninger

When GM discontinued 215 they replaced it with a derivative iron V6 that shared a number of parts. (V6 front cover and oil pump bolt onto 215, providing an easy solution to old-engine oil pressure problems, plus the filter mount is at a better angle.) The GN motor is from that lineage.

"Ford T5" is an odd term to throw around. T5 was a Borg-Warner transmission, used by both Ford and Chevy, but it'd be more convenient for you to use the Chevy version because it bolts to a GM bellhousing pattern. There are other differences...

IMHO there's no reason for - or excuse for - running side exhaust on any MGB. Installing a GN motor in MGB will almost certainly require designing and fabricating your own motor (and tranny) mounts and exhaust plumbing. If you just want to buy parts and bolt them together, the job isn't for you... but sure, the Buick V6 was used in lots of cool race cars (including Camel GT) and there's lots of support for it. I haven't seen one in an MGB, but it could be done.

I have little intention of running side pipes on the car. I'm spending most of my time running through the numbers, and designing bracketry for the engine/trans combo, I may have to design a whole new tranny crossmember instead for the combination. Not the simplest thing in the world since you have to *shudders* do all the geometry of the car's current set-up and reverse its engineering to develop the car's new parts, and it'll also require devloping the car's current power to weight ratio and handling characteristics, to the new handling characteristics and power to weight ratio's. So far from what I've been able to determine in autocad designs and automotive road profiler I should have an increased boost to overall performance but sacrifice at least 10% of the car's handling from the mounting position and broader weight disbursment of the engine and tranny. This is actually easily correctable by updating the bushings, and rack & pinion steering to a quick ratio set-up.

The rear end of the car though is my biggest concern as I will have to adjust the rear end to better accomadate the increased amount of power, and inprove its handling and traction ability through the aftermarket route. Though it is easy to upgrade the rear end to a coil over shock system thanks to a handy kit from Summit. The gearing of the rear end will have to be changed to a V8's specs. All easily done mind you but its a rather drawn out process, one I can assurdadly avoid by switching over to a GM fixed rear axle from a Nova II model, it'll be cut to the mg's stock length but have better gearing and a stock appearance (amazing what you can do with automotive design ain't it?) by using the rostyle bolt pattern.

I've decided to scrap the original fuel tank and use a fuel cell from RCI (15gal) in its place. I can mount the fuel cell inside the trunk on the forward shelf between the trunklid swing arms and still retain the original spare. While I will lose roughly 2 cubic feet or so of the trunk, its something that can be easily undone by future owners of the car, well if i ever decide to sale her which won't be happening period. The FI fuel pump, accumlator tank, and carb pump (no choice but to run an accumulator tank) can be safely and conviently placed inside the driver side battery box. The battery itself will be mounted in the passenger battery box as usual. Since I've decided to run with a turbo set-up, and no there won't be an large guagy intercooler seen or mounted anywhere on the car! I may be far from purist but even I have some exterior styling sense. The turbo's will be mounted on the rear of the car where the old fuel tank used to be, this in turn will keep the car's rear handling at or roughly at the original spec's of the handling range.

Since the turbo's will be mounted in the back, the return pipe to the engine compartment will be cool or just as cool as if an intercooler had be mounted to the car, this method has a minimal drop in overall boost mind you. The engine has been dyno tested already and produces 245hp at the flywheel, with turbo it produces 302hp at the flywheel, take into account the trans, and rear end's spinning mass and the total BHP at the rear wheel will be roughly 275bhp depending upon gearing of the rear end, how the transmission is built, its overall characteristics, and its type of build (full race, strip/street, or plain old street).

Thankfully I can keep the costs of the build down since I already recieved the biggest peice of the cost for free, namely the 3.8L engine and GReddy type 18G turbo's. Getting the engine dyno tuned was actually fairly cheap thanks to the buick club letting me use their dyno machine for free. Most of the parts and such I'm actually in a position to recieve for free or at cost, which should keep the build cost down to roughly 2k mostly for having the engine brackets, trans member, and rear end custom made for the car, and then the aftermarket FI, and assorted parts making up the bulk of the costs.

Oh and thanks for the pics and information guys! I really appreciated it! It made coming up with the designs that much easier for me as a whole!

Always biting off a huge chunk more then he can chew,
C. J. Dark
CJD Dark

I can't imagine your install beinging harder than a 302.
Do you have to cut the cross member,make your own header's,or cut the fire wall.
Is the engine rebuilt or put in as is.
Seems to go to all the work to install any engine
at least if it is higher mileage to overhaul it.
A lot of us like the stock look but it is not always possible. For guy's like me it's great having people like you doing the thinking,knuckle busting,trial and error so than you can share the do's and dont's.
I took the easy way I did a 3.9 Rover,you just buy all the parts and in no time you have a MGBV8. I love my car the way it is but if to do again I would do the 300
Buick,same fit some what but a lot more torque,for not so much weight.So really think it over nothing beats the V8 when it comes to the torque and that is where the fun really is. There are guy's who had there motor's and changed there mind's and used another. Nobody can predict the future I wish I would of given mine more thought because going the easy route isn't for everone. Please keep us posted we are all here because we truly belive there is nothing better than a Little British Car with more POWER,any POWER. Good luck it sound's like you have done your homework now go out there and get it done. Denny
dbw morris

CJ, you might want to rethink a couple of things.

First, if you put the turbos that far away from the heads the gasses will cool down very significantly and you will lose a great deal of boost potential before they hit the impeller so I think you will be disappointed with the results. Secondly, with that much tubing between the exhaust ports, turbo and intake ports, turbo lag is going to be a very real issue. Strike that, a very real *problem*. The reason it will be a problem is because of the vehicle you are using, in combination with that powerplant. As one of the extremely few people who have actually owned a turbo V-8 MGB I am qualified to point out that this combination has serious problems, the most important of which is the extreme potential for loss of control of the vehicle. This problem is almost entirely a result of the turbo and it's inherent power adding characteristics as well as turbo lag. The GN worked well with the turbo, but some reasons for that were that is was not designed as a sports car, it is more suitable for straight line accelleration, and it is a good bit heavier than the MGB. The MG otoh is designed to be flung through the twisties, does not have much emphasis on drag racing, but rather is built to achieve speed through handling. The problem is that the MG loves to have the pedal mashed as you exit the turn, and this pretty much applies regardless of what engine you have in it, until you add a turbo. Then all hell breaks loose because the turbo adds power suddenly, upsetting the balance of the car and throwing the rear end to the outside, and while this may be fun sometimes, it definitely is not fun all the time, or more accurately it is no fun at all when you aren't expecting it. Add in a healthy dose of turbo lag and you can never again predict with certainty just how hard you can hit the gas coming out of the turn. So if you drive in a spirited fashion this means that you will at some point lose it. On the public highways this is almost always costly.

Now I realize that there are turbo rally cars, turbo road racers, and so on, but those are not street driven cars, they are highly specialized, and their drivers are highly trained and equally important, have the luxury of concentrating solely on the task of driving, while in a heightened state of awareness while repeating the same course until a high degree of mastery is achieved. And that's very far from street driving.

Please consider an alternative. One that I would suggest is the V6 with a roots type blower. GM sold quite a lot of cars in this configuration so that powerplant is nowhere near as rare as the GN, it has smooth power delivery across a very wide powerband, high output potential, probably at least as high in terms of useful power as the GN, and the installation would be way simpler.

Your V6 installation should not be difficult. The BOP/Rover installation is the same engine with two more cylinders, so the same mounts can be used, engine position can be similar, most parts are available and hood clearance with the blower is most likely not a problem. The engine can be moved further forward to allow room for the auto tranny if you like, which should just about eliminate any need to cut the firewall or transmission tunnel. A 700r4 tranny should be more than adequate and there are many other good choices.

It sounds like an easy swap, but I would definitely look into the blower motor. I believe they were available with the Eaton M-45 and M-60 in Buick and Olds sedans just a few years back, but I don't know if they are still being produced. I yanked the turbo off mine after one too many spin-outs on the freeway and replaced it with an Eaton and have been extremely happy with that decision. So much so in fact that I would do everything I could do to convince you that you will be pleased with the blower, whereas you will find the turbo installation to be nothing but trouble.

Jim Blackwood

DBW: The engine is fully rebuilt by GZN Performance of Houston. I won't be cutting the firewall now, as I found the correct mounting position for the motor and tranny. The tranny crossmember is being scraped for a custom built one based on my own design. The front crossmember won't be cut either, but I will be moving the radiator 2" forward to make getting to the steering box a little bit easier for me for when i need to change its fluids. I won't be using High Performance headers, instead I've opted for a non-turbo 3.8L exhuast headers in a 2 to 1 configuration basically its what you'd find on a single exhuast car one header connects to an outlet pipe that routes under the oil pan to the other exhuast pipe where they meet and then travel to the back of the car. The one's I've found are from another GN 3.8L built in the early 80's that are basically block huggers. It'll double the exhaust pressure to the turbo, since I've dropped from a twin to a single slightly larger turbo to be centered in the space the old gas tank used to be. I'll retain the look of the dual exhuast from there by splitting the output gases out of the flange and running them out the back. Since the return pipe will follow the other side of the car, it'll still give the impression of dual exhuast until you open the hood.

Jim: I've had any number of car's with blowers installed and have grown rather annoyed with them as a whole, which is why I prefer turbo's as a better option. It's just a personal oppion in my case. As for the heat = power issue, its not an issue, the turbo is driven above all else by exhuast pressure, and if your exhuast system is fully welded up and built correctly it won't be an issue. Jim please consider that intercoolers are just that, large air coolers so heat isn't what's needed for the turbo to work correctly at all, its all pressure exhuast pressure, and return pressure.

While true that having the turbo further away from the engine isn't generally thought of as being a good idea considering the exhuast pressure deminishes by 1psi every 12" from the engine, its really a marginal loss overall once you take into consideration that I'm not looking to make 40psi+ from the turbo considering the needs of the engine only really require 10-15psi depending on the amount of power you desire to make, turbo model, and length of pipping (Which in an fairly large intercooler is nearly the same length of pipping I'll be running as a return). The buick model with the super charger you spoke of only makes 5psi total before you need to redo the pulley to make anything higher then 5psi, or buy a 3k dollar SC that isn't really an option at all. You see the model of buick your speaking of uses a completely different engine then what I have which hasn't been made in well over 10 years. The Buick Grand Nation had the last of the 3.8L motors, with the Pontiac Trans Am Turbo in 89 having a completely one off custom made 3.8L based off of the GN's motor. This motor essentially is hard to come by, and such performance parts as a SC was never really built for the GN car's since they were built using Turbo's in the first place.

As for the GM V6 SC motors, true you can find them if you look enough, but their also limited in power the highest HP motor I've ever found for a super charged V6 is 260hp and that was a GM built Crate engine from GM Performance. Compared to the un turbo charged GN motor the HP numbers are the exact same, but with a turbo those numbers jump straight up to 300-310HP. Also consider if you will Jim that turbo's have made leaps and bounds over the years in their design and construction thanks to the import racers and now have a larger range of power across the entire band then they did in the 80's and early 90's where as the SC is still made very little progress in terms of its own design and its range of applications over the years, and it still robs power from the engine just to operate it unlike turbo's that use only the exhuast pressure and nothing else, well past what it has in common with a SC being the need for oil feed and return lines. And before you say AH HA Jim, that's already been compensated for in my designs, with the use of a TarCat remote oiling system built specifically for rear mounted turbo car's such as the Camaro Turbo model, and other assorted rear mounted turbo cars. It's a clean set-up overall.

Please understand Jim I've already thought of everything you wrote well ahead of time before I started designing, and have done full comparasions on both set-ups in price terms, design terms, and amount of labor required to make them both work. The turbo is by far the easiest and most simplistic of them both in terms of power, overall performance, and reliability. Trust me if there was a way to make an SC work well on this motor, I would have gone that route. But since there isn't, I'll be going this path until someone decides that maybe they should design a better SC instead of using the old tech that's been around since the early 90's!

Chase J. Dark


I think C. J. is on to something here. I have not heard of remote mounting a turbo 'til this thread, but it's out there. Sounds very interesting.
Carl Floyd

This thread was discussed between 11/03/2005 and 24/03/2005

MG MGB GT V8 Factory Originals Technical index

This thread is from the archive. The Live MG MGB GT V8 Factory Originals Technical BBS is active now.