[czar97]

I’ve had my 72 Lemans for 32 years now. Dual 1 7/8” exhaust with Walker mufflers and 2” tailpipes straight out the back under the NOT notched-out plastic rear bumper valence. Both Walker mufflers are blown out the bottoms.
Time for all new starting at the backs of the stock exhaust manifolds (2 bolt). Just changed the 2 bbl carb for a Cliff quadrajet.
I’m almost certain I want flowmaster 40 series. Takes me back to car shows of the 1990’s.
Maybe a 2.5” exhaust system. Seems large for now but who knows if a larger engine is in my future.
So, what no-muss no-fuss system am i looking at? Summit, Jegs, some kit from another supplier? Maybe it’s cheaper to buy it piece by piece instead of a kit?
Another question, should my ‘72 Lemans be exiting on the side of the quarter panels on a downward and outward angle (behind the rear tires)? Or straight out the back like I have it?
Thanks for any thoughts.

[1965gp]

I have the traditional flowmaster 2 1/2” kit on my stock 70 LeMans and 69 GTO both with manifolds and I am extremely happy with the sound.

I bought both kits from summit.

I had the 70 LeMans kit installed, I installed the one on the 69 GTO. Easy to do yourself. If you aren’t running headers then you probably need to buy 2 1/2” down pipes. I bought them from summit as well (Pypes brand). Just trim to fit.

I found it well worth the extra $60 to buy the 2 1/2” x 3” band clamps if you aren’t welding. It made for a secure connection especially where you trim the down pipe.

I believe 72 had the exhaust below the quarter- like a 77+ Trans Am.

[Goatracer1]

If you look at the systems sold at Jegs, Summit etc. you will see they are usually for cars with headers. There are no down pipes from the engine.

[Scarebird]

2-1/2" pipes are SIGNIFICANTLY louder than even 2-1/4", even with 20" case Dynomax units.

That, coupled with DroneMasters you may regret.

2-1/2" downpipes, Dynomax's and 2-1/4" tailpipes will flow excellent and not beat your ears flat.

[The Champ]

2.5" RAm Air exhaust maninfolds into 2.5" pipes with x through 2.5" DynoMax 17749's exiting through 2.5" splitters.

Will work with the existing 350 and almost any engine change you might do in the future.

[Mister Pontiac]

One other thought... regardless of which system you end up with, maybe also go for the repro 72 GTO or 72 LeMans GT side splitters that exit behind the rear tires. You can just make them out in the photo below. They point out just behind the rear tires.

While not original to your LeMans, they are correct for the year, and I think they look nice (I have them on my 72 GT). The sound is also nice, especially when driving along any highway K-rail with the window down.

[Scarebird]

[czar97]

It really sounds better with splitters? I would not have guessed that.

[AG]

Originally Posted by The Champ

2.5" RAm Air exhaust maninfolds into 2.5" pipes with x through 2.5" DynoMax 17749's exiting through 2.5" splitters.

Will work with the existing 350 and almost any engine change you might do in the future.

This is the perfect system. I have RA D-ports manifolds and custom bent 2.5" exhaust with Dynomax 17749s and I love it.

[Mister Pontiac]

Originally Posted by czar97

It really sounds better with splitters? I would not have guessed that.

It's not because of the splitters per se, but the side exit. The exhaust note reverberates off of any wall you pass by giving a nice exhaust note, especially with your windows down.

I compare side by side with my 71 GTO that has factory rear exit splitters thru the valance. It sounds great too, but doesn't reverberate the way the side exit does in those circumstances.

Different flavors.

[DavesGTO]

Always had 70 GTOs and now with a 72 another benefit I have found is the rear bumper is better off if the exhaust doesn’t come out the back. I have noticed the sound benefit too.


Sent from my iPhone using Tapatalk

[The Champ]

Originally Posted by Mister Pontiac

It's not because of the splitters per se, but the side exit. The exhaust note reverberates off of any wall you pass by giving a nice exhaust note, especially with your windows down.

Reminds me of when my grandson (now 27 and a Marine crew chief for an Osprey tilt rotor aircraft) used to be cruising with me in the GTO. When ever we went under the pedestrian overpass by the college, he say "Grampa, rap the pipes..."

Sidewalls and a ceiling tripled the sound!!!

[OCMDGTO]

2.5" mandrel bent straight out the back. I'd be looking at Pypes

[tjs72lemans]

I bought a stock kit (2 1/4") for my 72 Lemans Sport from our sponsor and put it on in my garage. I didn't want any issues with fit. It worked very well with the side exit and splitters. Now that it's on, I wish I would've known I could've fit a bigger 2 1/2" on my stock exhaust logs. I may still do that, since that may be a benefit while leaving the rest as is. It sounds fairly quiet while cruising with a nice sound while idling.

[The Champ]

tj

I believe your stock exhaust manifolds are 2.25". I ordered the 2.5" RARE exhaust manifolds to accommodate 2.5 downpipes, mufflers, tailpipes and splitters.

[b-man]

Originally Posted by tjs72lemans

I bought a stock kit (2 1/4") for my 72 Lemans Sport from our sponsor and put it on in my garage. I didn't want any issues with fit. It worked very well with the side exit and splitters. Now that it's on, I wish I would've known I could've fit a bigger 2 1/2" on my stock exhaust logs. I may still do that, since that may be a benefit while leaving the rest as is. It sounds fairly quiet while cruising with a nice sound while idling.

You can buy 2-1/2” down pipes that fit the stock logs however they’re all made with a short section of 2-1/4” right at the flared end that mates up with the manifold.

So you can take advantage of a larger down pipe than 2-1/4” but again no 2-1/2” pipe is going to mate directly up to the manifold.

PYPES stainless steel headpipes/downpipes (p/n DGA10S-1 & DGA10S-2). I measured the inside diameter of the pipe at the flare and came up with 2.100", essentially the same ID as a 2-1/4” exhaust pipe.

[tjs72lemans]

Thanks for the pics and info.

[czar97]

Okay. First, thank you much for the thoughts, ideas and suggestions. Here’s where I’m at currently.

DGA10S which is the Pypes stainless steel down pipes. I believe that number on Summit is for both $160ish.

Flowmaster 17107 kit FLO-17107 $479. Steel (any issues with steel against stainless steel Pypes down pipes?)

OR

SUM-680121 Kit

The only thing I can’t figure out is where (or how to tell) where the tailpipes exit. Straight out the back or bent and 45 degree pointing down behind the rear tires (which is what I’d like… out the side behind the rear tires). Both kits appear to be straight out the back.

For the mufflers… super tough decision, but I’m going with drone-master 40 series.

[1965gp]

Looking at the flowmaster website it looks like it has straight out the back for exhaust tips or straight out with turn downs which is what I recall from the kit. You may be able to trim the angled turn down pieces shorter, turn them to the side and put your tips on.


Edit- Actually- Pypes offers these for $60 which will solve your problem:

https://www.pypesexhaust.com/product...ainless-tga10e

[tjs72lemans]

If that kit says out back, that's what it is. They do sell the tail pipe kit that exits the side like in 72.