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MG MGB GT V8 Factory Originals Technical - Exhaust pipe location

Running an Olds 215 block, 300 heads, and Chevy 305 pistons, Kenne-Bell cam, with a 215 crank, stock clutch with McLeod HTOB, and T5, in a '68 BGT. I have a question for you gents who have had a shop run a single exhaust pipe back from the header collectors. My shop will run 2-1/2" aluminized pipe back from my RV8 style headers with 2" collectors, to a muffler located under the boot floor. They asked me 'do I want the pipe to run over the rear axle, or under it?' They'd prefer over if there's room, and so would I. Any comments, especially from those who've run it over the axle? Does anything hit when the rear springs are compressed? Also, I have Konis on the rear; how big an interference issue does this present? Advice appreciated. Best, Joe
Joe Ullman

Mine ran under, and any time I want to change rear springs, I have to detach the exhaust mounts and let it hang low.

Annoying....
Justin

So, exactly how often are you changing your rear springs? For me, the concern is whether a single 3 inch pipe will rub over bumps...if so time to make it fit over the axle!
G.P. Copes

I've run it both ways, but only up to 2-1/4" For aesthetics, over the axle is the way to go although either way can be made to work. However, I was forever dragging the exhaust system no matter how I routed it with any configuration except the current one. The more you can tuck it up out of the way the better, and with it below the axle it's a bit difficult to get it to lie up close against the floor pan, and again to tuck the muffler up beside the gas tank. Aside from which the axle has a tendency to tag the exhaust when cresting hills and then there's the brake cable to worry about. But again, either way will work and it mostly is a question of ground clearance. Which I have little of.

Jim
Jim Blackwood

Yes, I hear ya on clearance. Think I'll tell 'em to go over the axle, but use their own judgement on 2-1/4 versus 2-1/2 inch pipe. The bigger 'looks' right, so hopefully they'll be able to bend it enough to get it up out of the way.
Anybody know of the tube shocks giving the pipebenders difficulties? If so, I guess they'll just have to deal with it.
Now to get a temp brake light setup, and find a few days with no rain so I can towbar her over the mile or so to the shop. Thanks, Joe
Joe Ullman

I have dual 2" tailpipes over the axle with tube shocks.It is tight but they have been there for 6 years.On a real nasty frost heave (thats a dip in the road for you lucky warm climate types) it does bump against the bottom of the car, but I live with it.It's nice to never have to worry about ground clearance issues.
Dale

Thanks for your comments. Dale, did you move the gas tank, or did you run both pipes together up under the left side? Best, Joe
Joe Ullman

Joe,I (correction:the guy I had do the exhaust) ran them both on the left side.Two small turbo mufflers about under the seats,the right side pipe exits the muffler and crosses over in front of the rear axle. It's all stainless and I haven't had to touch it since new.One each side would have been nice but at the time I wasn't aware that moving the tank was that common a practice.Oh well,next time...
Dale

I vote for over the axle if there's room. I ran mine under and the axle rests on the exhaust when changing the tire on that side, not the best thing to risk breaking an exhaust hanger on the side of the road while changing a flat. Next time it will go over.
Bill Young

I ran 2" from the head pipe to a turbo muffler under the driver's seat, then 2" pipe over the axel and out in the stock location. Mine's a 66, and I removed most of what was left of the 6-volt battery box. I'm pleased with it, although the muffler is the low point. It doesn't sound obnoxious at all. I'd thought about using a Thrush Glasspack (against better judgement) by the gas tank instead of the turbo under the seat, but they don't have a 2" one short enough. I don't like the glasspack sound, but was willing to make the sacrafice for the additional clearance below the car.

I also had the lift the axel with the exhaust pipe syndrome prior to the change.
Glenn

At one time there was a turbo type muffler available that was short, round, and just a bit larger in diameter than a glass pack. I had one on my car with the stock engine and liked it very well. They were available for different pipe sizes. I'd think they could still be had but haven't seen one in years.

Jim
Jim Blackwood

I haven't looked into it, but Summit Racing sells a 12 inch long, 3 inch diameter muffler from a company called Car Chemistry, Inc. I can't imagine that they do much - anybody know??

Wayne
Wayne Pearson

Just wanted to share, that Flowmaaster has a new quiet muffler (good sound) Which will be introduce at SEMA. Small muffler that can be fitted in tigh places, and produces a bit more torque etc. It should be on the market by Dec time frame.
Bill Guzman

good call Bill! I will have to keep my eye on that. I was wondering if they would ever get to the crowd of peeps with the rail 38's and modded 50's cars that want have the modern power and performnce, but to hide everything and keep it quiet. That is becoming much more popular it seems.
Larry Embrey

Wayne,
I called up Car Chemistry to inquire about those particular modular mufflers. After questioning the rep, in the end it was evident that they'd be too loud for my purposes, even with the 'shutters' closed down to direct most of the exhaust thru the core. Asked if they were louder than a Flowmaster, "Oh Yeah". Those shutters remind me of the "Snuff-or-Nots" of the 60's, that you could put into the ends of your straight motorcycle pipes, and actually worked pretty well..at least on my rather small, 305 cc, bike. These can be seen at www.carchemistry.com.
Everybody's comments have been extremely helpful, and gives me more stuff to talk about with the pipe benders. Thanks, Joe
Joe Ullman

When my muffler was fitted I asked the guys doing it to try and fit a muffler up into that space before the back axil, as well as one after. They found/fitted a stainless 2.25 inch muffler "off a 3 litre six cylinder BMW". Thats all they would say. Might be usefull to you, good luck.
Peter

Thanks, Peter, that's worth looking into. Joe
Joe Ullman

As it turns out, we went with a 2-1/4" system, with the oxygen sensor fitting just aft of the Y. The muffler was a round Magnaflow, pn 12615, 14" long and 6" in diameter, that tucked up real well along the left side of the fuel tank. Can't tell ya how loud it is......cause it don't run...yet. Needs fuel lines and all electrical, hydraulics and a few other things like dash, glass, and interior. Next on the plan is to finally change out the splined hubs this winter, fit wheels and tires, get the Fiero seats mounted up. Then, to get it running. Hopefully, now that 'most of the dirty work is done', I can spend more time evenings on fun things like wiring and brakes. It's been seven years already, but need to have it done in the next two or three. Best, Joe
Joe Ullman

This thread was discussed between 04/11/2003 and 14/11/2003

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