Welcome to our Site for MG, Triumph and Austin-Healey 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 - V8 Exhaust

Please help me with the exhaust requirements and problems. I am putting 2 inch headers on my V8 engine. I do not want dual exhaust but want to merge the headers into one common exhaust pipe. What are my issues? Thanks. Jack
Jack Joyce

Unless you are running a BBC or other very large motor you do NOT want 2" headers.

1.5" is more than enough for a Rover, 1 5/8" is even on the large side. Take into consideration that the 5.0 guys are all running 1 5/8" as a upgrade and those motors are 100cid larger and flow lots more air.. Too big a header will drop backpressure and hurt torque.

I would say 1.5 or 1 5/8" header tubes into 2 or 2.5" single exh out the tail would be perfect.

If you are handy with a welder, get some bends from your local muffler shop and start piecing it together.. HArd to know what issues you may have without being under your car..
Larry Embrey

I was gonna say 2" is WAY too big for our cars. I did basically what Larry said. RV8 headers going down to a single flowmaster under the drivers seat, and a single pipe going out the back. Sounds JUST like a 5.0 Mustang. Lots of people ask me if there's a 5.0 in it it sounds so good! I would recommend putting a heat shied between the muffler and the floorpan. Sometimes my floor gets so hot I can smell the carpet melting -- not good.


Guys, I seriously doubt Jack was referring to the size of the primary tubes. More likey 2" is the collector diameter.

Jack, unless you are running big HP a Y pipe into a single 2.25 or 2.5 will more than do the job. There are no issues. More of us run single exhaust than dual. You might want to seek the help of a reputable muffler shop.

On my first V8 conversion (before going to dual exhaust) I used the block hugger headers with a Y pipe into the aftermarket Monza exhaust system that I used with my stock 4 cylinder engine. I purchased the Monza system through the British Victoria catalog. I have a 78 MGB but when I ordered the Monza exhaust I ordered the one for an earlier year that did not require a catalytic converter. Never had a problem passing emissions with the 4-cylinder engine or the V8 with that exhaust.
I however really appreciate the sound coming from dual exhaust with the V8; there just isn't any comparison, to me the duals sound so much better!
Michael S. Domanowski

That they do Mike, and I'm sure they help more than a little when you hit the nitrous, eh?
Jim Blackwood

Hi - Thanks everybody. I was referring to the collector diameter. These are R8 headers I bought with the engine from D&D out of Michigan. I thought that I might have an issue bringing the headers into one exhaust pipe. I am trying to select the proper sized pipe so as to not lose much of this expensive horsepower I bought. The muffler(s) might be an issue too? I appreciate your comments and further advice. Jack
Jack Joyce

I'm about to do what you're doing. I'm thinking 2-1/2" exhaust, but welcome suggestions. Flowmaster 500 series mufflers are supposed to fit well, but I haven't decided whether to locate the muffler under the l.h. seat, or back under the boot floor. Also, an outfit called Genesis, 1-800-274-8437, a division of Thermo-Tek makes some modular mufflers that might be worth looking into. You can bolt sections together to make it quieter or louder, different sizes, stainless, hi-flow, etc, they say. Also, there's a picture of the exhaust system under the car at: Sorry, still don't know how to make hotlinks here. Best, Joe
Joe Ullman

Jack, I just completed my exhaust system with a setup that might work for you. I used RV8-style headers with 2-inch collectors. I ran 2-inch pipes from the collectors to a Flowmaster Y-Pipe that has dual 2-inch inlets and a single 2 1/2 inch outlet. A Flowmaster series 50 muffler that fits beneath the drivers floor connects directly to the 2 1/2 inch outlet from the Y-Pipe. A 2 1/2 inch tailpipe and Hooker Header chrome tailpipe extension finish off the system. Sounds real good! Rod
Rod Holderbaum

Is the dualies' better sound due to the stereo effect, or what? For my conversion -- in process; going OK, thanks -- I'd like to keep a single tailpipe because I think it looks more MG-like ... or would that sound worse and be less efficient than a true dual setup? I guess the compromise would be to rig a dual setup but have both pipes right next to each other on the LHS of the rear valance.
Sam Peeterson

A friend has one of Towery's 4.6 liter GT's with duals exiting together in the stock location. The left muffler is under the driver in a north-south attitude with the right one under the passenger area yawed about 30 degrees. No balance pipe. It sure sounds good.

For just about any V8 with medium power and street driven car. The primary pipes should 1 1/2 or 1 5/8
With 2 collector, and like Carl suggested use a "Y" pipe with single exhaust into a single 2 1/2 using a free flow muffler from Dynomay. This will produce the must torque from idle to about 6 thou rpm and if larger collector then larger single pipe for lots of hp output engines. Many racecars use the single exhaust with a Y pipe.
Bill Guzman

I beleive the reason for the use of smaller primaries is to keep up the speed of the gasses exiting, not to create back pressure. The only engines with which I am familiar that require a certain amount of back pressure are crankcase scavenged two-strokes. Repowering truck specifications will only show a maximum backpressue figure, with no minimun.

FWIW, George
George B.

Jack...THere is a stainless steel y-pipe available for the MGRV8 headers. I got mine from D&D.

rick ingram
rick ingram

You might want to think about shifting your hydrolic clutch line, pointing it forward, it's a little close to the exhaust.

This thread was discussed between 04/06/2003 and 09/06/2003

MG MGB GT V8 Factory Originals Technical index

This thread is from the archives. Join the live MG MGB GT V8 Factory Originals Technical BBS now