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MG MGB GT V8 Factory Originals Technical - Buick 215 vs. 300 manifold

Hi guys, I have a question. The 300 buick motor I understand is a cast block with alum. heads.are the heads the same as 215 buick. I am looking for a set of exhaust manifolds for 3.9 and have seen both 215 & 300 manifolds for sale.

Thank you

Paul
P Harrington

Exhaust manifolds? You can't use buick exhaust manifolds in an MGB. you need to use manifolds specifically made for this application. You have two options:

1) block hugger - They go down between the chassis rail and the block. They're a cleaner installation, but they rob power because of all the tight curves in them. They also have a tendancy to crack.

2) RV8 style manifolds. These require cutting the inner fenders and running the exhaust down into the wheel wells and then back to the rear of the car. Yes, you have to cut your car, but it allows you to use a better exhaust manifold, and when driving, the wheels are low pressure areas and they suck the hot air out of the engine bay. Double bonus!

Justin
Justin

The article I read talked about boring the cylinders of the 215 to increase displacement and using the heads from the 1964 (the only year they were aluminum) Buick 300 because the 300 have bigger valves. I didn’t figure out if the bigger valves would foul the standard cylinders of the 215, but they do bolt on. As I recall the exhaust ports of the 300 were bigger so the 300 Buick manifold was required even though the 215 manifold would bolt on. From all that I would think the 300 exhaust manifold would work on the 3.9 Rover and allow you to increase the port size. As Justin says, it won’t fit in an MGB and neither will TR-8 manifolds (I tried), but they do bolt on.
George Champion

Thanks for the comments. I was looking at the MG V8
convention website ( it was a little outdated ) but it showed a picture of under the hood of all the participants, and also listed all the engine components including style of exhaust. Kurt schley had a buick 215 with a buick 300 cast iron exhaust manifold in a 1974 mg, chrome bumper to boot. So I am confused. I am building my 3.9 and will be trial fitting shortly ( in a 74 gt ) and would like to get away from cutting up inner fenders for headers, I under stand the heat build up issue also. So how did he do it?

Paul
P Harrington

I'm sure Kurt will respond and tell you how he did it. I had a real thing against cutting up my car until I started cutting. :) It's worth it to go the RV8 route. You eliminate so many problems that way. You can cut the holes very tight if you want, or add removeable panels to go around the holes so they are less visible, or just leave them wide open. That's what I did, and it seems to be what a lot of other people do too. If you use block hugger headers you'll probably rub your steering column, or come darn close to it, and you'll be dropping an extremely hot exhaust manifold next to the starter solenoid. That's not the best scenario by any stretch of the imagination.

Justin
Justin

Paul,

I spoke to Kurt Schley briefly a few years ago and although I don’t remember talking about the exhaust I do recall him saying about not using the conventional route with the steering.

Before starting my conversion I was sure the 215 manifolds would work, but once I had all the parts in hand I could see the exhaust would exit into the passenger area. From photos the 300 manifolds exit in a better position, but must still be the hard way to go. The TR-8 ones I tried required large openings into the wheel wells and the down pipes would have been close to the brake lines and would nearly touch the frame rails. Save yourself the expense of buying those old manifolds and use the money on headers that were designed for this motor in this car.
George Champion

Thanks guys, Unless Kurt comes back with a slick way to do it, I am convinced to go the rv8 route. I am always wanting to do something a little unique, but not this time. Thanks again, Cheers! to a great forum.

Paul
P Harrington

other than the Heat issues - of which I have plenty- 60,000+ miles on a 3.5L,(over 14 years) with block huggers and, as yet no engine steady bar, no problems... but the heat may lead me to eventually cut holes - but maybe just for louvers for now!

Derek
Derek Watson

Hi Paul,
I did use Buick 300 cast iron manifolds on my 215...BUT:
1) That was 15 years ago when tube headers were not readily avaialable and were very expensive.
2) I was on a really tight budget and was using anything available.(still have only about $3000 invested in the car.)
To use the iron manifolds I had to put three U-joints in the steering shaft as well as a support bearing, not the most efficient arrangement (though it has held up well over the years) I would highly recommend the RV8 style headers for both performance and, as importantly, for minimizing heat in the engine bay.
Best Regards, Kurt
Kurt Schley

Paul wrote: "I am always wanting to do something a little unique..."

In that case Paul, I think you should definitely take a crack at making your own headers. Making headers is alot of fun! They'll probably even fit better than RV8 headers since you'll probably locate your engine a little differently than RV8. You can buy a mess of pre-bent tube sections and collectors... or you can make your own parts. Sand-bent tubes are nifty 'cause you can have fewer weld joints, compound curves, and more organic shapes. The trick is to pack sections of tubing with sand, weld on temporary caps (leaving small vent holes) and then heat the tube just the right color with a torch while applying leverage around various diameter trees and fenceposts.

Years ago (i.e. before RV8) a buddy and I sand-bent a set of tri-y headers for my 215-powered GT. It was one of the most enjoyable aspects of our whole conversion! Here's a snapshot:
http://www.mgcars.org.uk/v8_conversions/engine/tubeex/p10mgbv8.jpg
(In the photo you can see that these headers unbolt at the collector to make installation easy.) These headers still work and look great, but if I made another set I'd probably route them out into the wheel-wells since you can have bigger bend radii, longer primaries, and easier starter access.


Incidentally, do store-bought RV8 headers bolt-up to Buick 300 heads? If they do, do the port shapes match up smoothly? I'm just curious.
Curtis

This thread was discussed between 17/08/2004 and 26/08/2004

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