65 riv exhaust

[gmdbhornet]

I read a post way back that said the 65 riv grand sport had 2 1/4 pipes. Were the 2 1/4 pipes all the way from the exhaust manifolds back or was it only the tailpipes. I have a non gs 401 motor and want 2 1/4 all the way back but the exhaust manifols only take a 2 inch pipe. Just trying to see if the gs had a larger diameter exhaust maniflod hole. Any help would be appreciated. Thanks. Gerry ROA # 11736.

[Jeff_Avery]

Hey Gerry, The 65 Gran Sports did have 2 1/4 inch all the way from the headers through the tail pipes. The parts are available from Waldron Antique exhaust. They advertise in the Review

[RivNut]

Jeff,

I think that when I read Gerry's post he's acknowledging the 2-1/4" pipes on the GS. His real question is "did the GS's have a different exhaust manifolds than the non-GS models?" I know there are quite a few diffenent external pieces for that A9 option - intake, carbs, breather, distributor, a/c bracket, kickdown bracket, etc. - but were different exhaust manifolds also part of that option? Here's where the real GS experts kick in!!!

The manifolds he has will only take a 2" pipe. My question is: Were perhaps the GS pipes tapered at the manifold in order to bolt up to the existing manifold? The aftermarket set I bought some time ago were 2-1/4" pipes the full lenght except for the first 2" where they bolted to the manifold - where a 2" pipe was welded on and the flange was for a 2" pipe. Because of this, they're still sitting in the basement in the orginial shipping container. If the factory pipes were like the aftermarkets, wouldn't the bottleneck at the manifold more or less deem the rest of the wider pipe to be of little value?

Ed

[John]

1965 Buick parts book shows Riviera GS uses same exhaust manifolds as others. Front pipes, resonators, muffler and tail pipes are different for GS. Rear pipes (over the axle) are same on GS as others.

John

[RivNut]

If the exhaust manifolds are the same and the tail pipes are the same, what good are 2-1/4" pipes in between them?

[Guest REX STALLION]

Sanderson makes headers to fit the `63-`65 Riviera 401 or 425. If you wanted the 2 1/4 pipes you could go that route.Heck you could run 3" if you wanted!!

[RivNut]

So does TA Performance. They're both "shorty" headers designed for 1st generation Rivieras. The Sanderson's have 1-5/8" primaries and the TA's have 1-3/4" primaries. From what I can tell, they don't bolt up to the stock exhaust pipes. Sanderson also makes a block hugger style header for the nailhead.

Ed

[95Cardinal]

The GS exhaust pipes offer a couple of advantages over the standard exhaust pipes. They are larger diameter AND they have different bend patterns, with fewer and shallower bends than the base system. The GS muffler also has larger inlet and outlet tubes with larger internal passages. The GS tailpipes are also larger diameter than the base system.

It's unfortunate that the GS used the common exhaust manifold, but after the first few inches, the GS system offers advantages all the way back.

[RivNut]

It still seem strange to me that if you're trying to scavenge exhaust away from the combustion chamber that the smallest opening in the entire length of the system is so close to the exhaust valve. It's kind of like trying to get out of a stadium after a game; no matter how big the sidewalk is outside, the jam still occurs at the door - in this case the small opening in the back of the exhaust manifold.

It would be interesting to see what kind of cfm's flow through the GS system if you could compare it to a stock system that had a manifold on it with an enlarged opening where it bolts to the exhaust pipe.