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MG MGB GT V8 Factory Originals Technical - What was I thinking?
|Here I've been daydreaming about upgrading to a Buick 300, or possibly even stroking it with a 340 crank, and all the while not one person on this board thought to suggest that the idea might just be a tad bit insane. So I go out today for a drive, and I've gotta tell you guys, when the car starts spinning the tires in high gear at 70-80 mph on the interstate it's got engine enough! What I'd better be concentrating on instead is getting it to run a little cooler.|
|Jim its time you changed the rear end. Drop in some 3.00:1's then when you can spin those in 5th at 80mph you have enough motor. I figure you should be geared for about 165+mph.|
But remember you can never have enough HP!
|Michael S. Domanowski|
|Having driven 150 mph in my wild and reckless (certainly not wreckless) youth I can honestly say that more than that is unnecessary for a street machine, especially in this day and age. Getting there quickly however never grows old.|
|"I figure you should be geared for about 165+mph"|
Download the chart at the link below, and find out for sure! (right click and select "save target as")
Plug in the tire size, rear axle and transmission ratios, and out comes the data.
I have an upgraded version of this for a 6-speed transmission I can e-mail to anyone if they want it.
|But Dan, I don't *remember* the overdrive ratio of a close ratio T-50. However, I know I ran those calculations years ago. 150 was the target, I doubt much has changed since then. I could look it up but it'd mean a walk out to the lab and it's too close to bedtime.|
|Jim, you weren't really expecting someone on this board to call you insane were you? Not from a bunch of guys who stuff big V8's and V6's into LBC's! To most of us that is just normal thinking. I figure that not one of us hasn't thought of adding some more horsepower to our projects from time to time. |
Wouldn't it cool better at 150 than at 75 with that much more air flowing through the radiator? You could take care of both issues at once! :-)
Go for the 340 stroked 300!! (Dan LaGrou has built one of these for Dave Michel)As long as the weight of the engine can be kept to a figure which still allows good handling, build the very largest engine possible.Too much is never enough!
|Well... I was thinking I *could* dial in some more downforce from the wing to keep the tires from spinning, that would probably be the right thing to do. Right now about all it does is push the rear end back down if it tries to float but since I have it I might as well use it. I guess some serious porting might be in order on those aluminum 300 heads but with the blower, maybe not. I already have a set of cut down SBC 2" journal rods so I'd need pistons, a bellhousing, and a stronger tranny, maybe a T5. This project may take as long as your new engine though Kurt. Still, as they say, there's no substitute for cubic inches.|
As for the cooling, without any shrouding around the radiator I'm not sure if it'll cool better at 150 or not. I'm thinking a crank driven 17 or 18" solid fan should do the trick though, especially if I build a fan shroud and finish blocking off airflow from around the radiator. Heck, it's a big 5 core brass radiator, it ought to work well. Probably just needs more airflow. One other thing I've been thinking about is that the coolant passages in the copper head gaskets may be a bit smaller than in the composition ones, but it does look like there is adequate coolant flow through the upper radiator tube so it's probably OK. Time to go shopping for a fan.
|Dave Mickel's engine uses a 350 crank, not a 340. CI is a bit over 350 as it is bored .060 over, like mine.|
Head work is really the secret, & installing larger valves so the engine will breathe enough to match the displacement.
I will be at the Rocks show this Sat. & a Deleware show on Sun if anyone wants a ride in the smaller 308 CI powered MG. Jim, if you get to the Nation's Capital, your welcome to some drivng time, as is any other V8 nut.
|Are the rod journals the same for the 340 and 350 crank? They have the same stroke so I'm just wondering what's different. Jim, thanks for the invite. I'll gladly reciprocate once I get the cooling problem fixed. And you know, a trip to DC could happen in the next year or so.|
|Can't answer that question. You might contact Dan @ D & D who would know. Simple answer may be that 350 cranks are easier to come by.|
|Jim - wasn't it you who wrote some years back that you do these things because you can !|
If you are still up for bursts of 150 MPH, shouldn't your suspension be the focus - the GT is close to flying at 130 MPH (Imperial measurement)
- and there are still a lot of folks out there who can use a tip or two from you.
|May have Roger, may have... I've had the car up around 130 without the wing and front air dam and it did start to feel a bit light. That was a dozen or so years back. Since the last rework I've only gone up to 120 and it felt pretty solid, but those next 30 mph make a big difference sometimes. The suspension is pretty basic. Lowered by a combination of spring and tire changes by about 2", the spring rates and shock action are both stiffened up a bit, V8 front bushings, and a GT swaybar on the front are all that's needed to give rather exceptional handling at that ride height. Sort of like comparing the CB and RB models, the CB which is lower handles better and needs fewer suspension band-aids. My car which is lower still reaps a similar benefit.|
Oh, and the car that I used to drive 150? A 1970 Olds Cutlass Supreme. With a few minor mods.
|> I'm thinking about building up a 300 to replace my 215 in this car: |
> I'm aware that the crank from a 340/350 can be used and requires a
> good bit of clearancing but was wondering about what's available for
> pistons? Can small journal SB chevy rods be used? What is the
> difference in deck height on the 300 and the 340/350? and finally
> will the aluminum '64 300 heads bolt to the 340/350 block? (I
> realize this causes a flow problem)
I meant to respond to your question over on the email list but got behind
on my email so I'll respond to it here. From my database, here's how the
Engine Years Bore Stroke Main Rod Rod Deck Pin
Diam Diam Length Height Height
215 61-63 3.50 2.80 2.3 2.0 5.66 8.96
300 64-67 3.75 3.36 2.5 2.0 5.95 9.50 1.831-1.842
340 66-67 3.75 3.85 3.0 2.0 6.38 10.15 1.831-1.842
350 68-79 3.80 3.85 3.0 2.0 6.38 10.18 1.800-1.855
The equation for stroker math:
piston pin height = deck height - (rod length + crank stroke/2)
Buick 300 with 340/350 crank:
deck height - (stroke/2 + rod length) = pin height
9.5 - (3.85/2 + rod length) = 1.8
rearranging and solving for rod length to use Buick 350 crank and pistons
in Buick 300 block:
RL = 9.5 - 3.85/2 - 1.8 = 5.775
RL = 9.5 - 3.85/2 - 1.855 = 5.720
Small journal SBC rods are 5.7" which is in the ballpark (deck block
0.020" if required). I think the stroke limitation is likely to be
the rod bolts coming too close to the cam so this would all have to
be mocked up and checked. I have an article about a 340 crank in a
Buick 215 and also Kurt Schley has a 3.75" stroke M/T crank in his Olds
215, so I believe it is possible. I don't know what the 350 pin
diameter is so they may or may not work with the SBC rods.
The Buick 340 and 350 cranks are the same, the difference is bore.
The 340/350 crank needs to have the mains turned down from 3" to 2.5"
to fit the 300 block but that's not a big deal. With 0.050" over
pistons, you'd have 350 cubes. I think the area of main concern is
rod bolt to cam interference.
I've been told there is an issue with '64 aluminum heads on '65-'67
Buick 300 iron blocks. There were supposedly some relocation of the
passages but I forget the details. I can track down the details if you
get serious about this.
The only aluminum intakes were the 2 and 4 barrel intakes made for
the 1964 Buick 300 with aluminum heads. If you need one to carve
up to make a blower base, I have a perfect 2 bbl intake. I've got
a perfect 4 barrel intake but the intakes are identical except for
the carb pad area.
|What a bogus piece of info, if your mgb was acctualy clocked at 150, you WOULD be airborn, front damm or not.We all know the V6,is far quicker off the line, saw one turn a 13 quarter this summer!|
|??? Brian I think you're out of line here. You should read more carefully, make fewer assumptions and be a bit less presumptuous. -Jim|
I certainly am interested in more details. So does that mean that the Chevy rods work with the 350 or 340 pistons to get slightly less than stock compression? I need to run fairly low compression with the blower.(rods can be reamed or bushed for the matching pin diameter) I didn't do a detailed study of your dimensions yet, still decoding. Apparently it shifted a bit. As for the water passages, I would think they could be matched up without too much work but won't know until I see them. As far as using the 340 or 350 block it looks like the additional height could be a problem. the 300 is .540 taller but the other two are almost an inch and a quarter more and this could create a problem with the headers, though not an insurmountable one. How it would affect the steering shaft I don't know yet as I haven't looked at it but I think there's room. Hood clearance is not an issue. I already have an intake, the 4 bbl one. I wouldn't think they are particularly scarce but could be wrong. Thanks for the info, I've found it most helpful.
As far as I can tell, there are no significant problems bolting the 300 heads to a 215. I started that project several years ago & a comparison of the head gaskets revealed no problems except the 300 combustion chamber diameter was larger then the 215 bore, causing a lip which I decided I did not like. Many engines have been screwed together this way, but it really drops the compression ratio.
Bryan, work on your reading skills. Jim claimed 150 mph in a modified Olds Cutless, not an MG.
I have a State of Maryland citation of 141 mph for a lowered '77 roadster with a Parrish hardtop & a LE spoiler & a very hot 215. Can't wait to find a safe road to open up the 300 GT & see if 160 is possible. It will go that fast on paper, but that is not the real world.
Some friends built a Ford conversion a few years ago & blew the rag top off at 125, scaring the s#@t out of both of them.
I believe thet Les Anderson's small block Chevy MG was running over 150 mph back in the 70's & there are topless SCCA racers with 4 cyl engines hitting over 120 on the straights on longer courses such as Road Atlanta.
Lots of V8 conversions are capable of low 13's, but it is all a matter of gearing. Pretty hard to do with the 3.00 cruiser rear most run, not a problem with the 3.9 gears in the stock B rear that lots of V6's run.
|The fastest Ive been going in an MG was my first GT on a straightaway in NV, got it up to 100 and then decided not to push any harder.|
If you have to turn down the rod journals anyways, you can get a different stroke by having the journals offset ground. + - .25" to the stroke depending on if you want a longer one or if it needs to be shorter for clearance issues. Just thinking out loud.
|"I have a State of Maryland citation of 141 mph for a lowered '77 roadster"|
And I have a new hero! Way to go, Jim. Wonder if I'll have the nerve to try that when my Ford/GT is finished.
|Jim, noted, sorry.|
|Jim, I have to dissagree on the 3.90 rear gearing being better for 1/4 mile use or high speeds in a MGB. The tires on a MG are just to damn small. I usually don;t even use 1st gear as all it does is get the car to 2mph before I have to switch to 2nd. I was out of motor (RPM) with a T5 trans, stock tires and gears well before I hit 100mph in the 1/4. I had to use 5th gear just to get acrost the line at 102, and that was lanuching in 2nd gear. YEs she had more mph once in 5th, but with 3.08's or maybe 3.27's 1st gear would be usable which should hopefully put the car still in 4th gear crossing the line which means it would be accelerating harder.|
Why use the higher rear end ratio and lose a whole gear?? gear up a little, use the torque and keep that 5th gear for 160mph+!!!
And as for the comment about the V6 running 13's in the 1/4, so what I have also seen 4cyl MG's running 13's and breaking 8" ford rear axles doing it.. My car has the power for 11's or low 12's, it just comes down to traction. Key is doing it and having a completely docile, bumper to bumper traffic friendly rig all in one without flipping switches, or dialing back boost
(no offense injended Jim B), or anything else other than controlling your right foot.
Sorry, had to vent a little bit.. I'll get off my soapbox and back into the garage now..
No disagreement with your observations. Tire size is an important factor in gearing. I run a 3.7 MGC rear in my roadster which sports a mild 215 and get very good acceleration, but I would not use that rear in my 300 GT. I also run 15" tires. I find 1st gear very usable in the roadster, but again tire diameter is part of the equasion.
I too have a goal of a daily driver that I can scare myself a little when the time is right.
I didn't think you were venting, just making valid observations.
It could very well come down to tire and engine set-up. I know the 302 and probably your 300 have more torque than they know what to do with, I figure might as well make it use that torque. The 215's are different as they are almost 100cid smaller.
I had a bunch of guys at work saying to go 3.55's I kept trying to explain to them I don't have a 3700lb car tp lug off the line like them and my tires are over an inch smaller diameter.. They finally understood when I took them for a ride. She will shred them off in 2nd gear all day long unless I feather the clutch and throttle to get moving.
|> So does that mean that the Chevy rods work with the 350 or 340 pistons |
> to get slightly less than stock compression? I need to run fairly low
> compression with the blower.(rods can be reamed or bushed for the matching
> pin diameter)
Not necessarily. I just ran the deck height numbers and out popped
a rod length similar to that off a small block Chevy. I didn't run the
compression numbers as I didn't have the piston specifics.
> I didn't do a detailed study of your dimensions yet, still decoding.
> Apparently it shifted a bit.
The forum software doesn't like spaces. I'll email you a copy.
Read it in a non-proportial font like Courier and it'll line up.
> As for the water passages, I would think they could be matched up
> without too much work but won't know until I see them.
The '64 300 head mismatch on '65 iron block was experienced by one
of the guys on the Buick small block V8 forum at www.v8buick.com.
It'll be a ways back in the old postings so it mght be easier to just
make a new post and see if anyone respods with details.
> As far as using the 340 or 350 block it looks like the additional height
> could be a problem.
The 300 block does look to be the best option. TRW Buick 350 flat top
forged pistons can be use in the 300 block with 300 rods but compression
is rather high. Without the stroke increase the displacement is around
> I already have an intake, the 4 bbl one. I wouldn't think they are
> particularly scarce but could be wrong.
Aluminum intakes for Buick 300's were produced in 1964 only. 1965-1967
Buick 300's were cast iron heads and intake. No aftermarket intakes
were ever produced. That makes them fairly rare.
> Thanks for the info, I've found it most helpful.
> As far as I can tell, there are no significant problems bolting the 300 heads
> to a 215. I started that project several years ago & a comparison of the head
> gaskets revealed no problems except the 300 combustion chamber diameter was
> larger then the 215 bore, causing a lip which I decided I did not like. Many
> engines have been screwed together this way, but it really drops the
> compression ratio.
The chamber overlap isn't much different than some Chevy small block smog-era
castings. It's not ideal but in practice doesn't seem to be a problem. Last
time I heard, Wil Bridges had nearly 100K miles on his 300-headed Buick 215.
The compression drop is mainly a problem on stock stroke engines. When used
with a Buick 300 crank, the compression ratio is in the desirable range.
Being aluminum, you can always weld up the chambers. A local head porter
offered to do the job for $250 (roughed-in with me doing the finish work).
> If you have to turn down the rod journals anyways, you can get a different
> stroke by having the journals offset ground. + - .25" to the stroke depending
> on if you want a longer one or if it needs to be shorter for clearance issues.
> Just thinking out loud.
Rod journals are already 2.0", same as the small journal Chevy.
|Bryan Heidtman you think 13's are quick? Please come to NY.|
|Michael S. Domanowski|
|Bryan, appology accepted, I figured it was just a momentary oversight anyway.|
Guys, you've really got me thinking here. At this point I'm really really curious about the possibility of bolting the aluminum heads to a 350 block. That would have the advantage of all stock internals I would think, and with the blower the smaller valves wouldn't be much of a disadvantage.
|heh we have a bunch of cars in this area (not MG's) running low 9's in the new heads up league we started this year. That is allot of fun to whatch!!|
If I had the time and $$ I would definitely be running a MGB GT car in the league with a 351W, tubbed, etc.. I had it all planned out and chassis and engine in line, but then reality struck..
|One of our local club members was clocked by radar at 134 mph a couple of years ago at the 'Chanute Chute-out'. He was running a large Rover version with Nitrous injection in a B roadster. This was from a rolling start in approximately 5/8 mile. When he cleared the speed trap the motor sounded like it was still pulling well, so I don't doubt that 150 wouldn't be out of the question. Definitely got airborn over the infamous 'hump' at the airport using airport transfers tonbridge track, but came back down ok.|
|Yeah these cars are wicked fast with the V8's in them. What is so amazing is how smooth they are pulling all the way thru!!!|
I got to put some miles on mine yesterday for the 1st time in over a year. Pulling away hard in 2nd was pure bliss. She would break loose a good bit, but even doing that she was accelerating hard.
Once I get a real rear end under the car and can run her hard I plan to make one more trip to the drag stip to see what she can really do.
This thread was discussed between 20/09/2004 and 03/10/2004
This thread is from the archive. The Live MG MGB GT V8 Factory Originals Technical BBS is active now.