[car guy]

I am doing some work to my 71 Lemans Sport Conv. this winter. Basically detail the engine compartment. While I was at it I thought it would be a good time to update my exhaust system. What I have is a bone stock numbers matching car with the 400 4 speed. I want to use D port RA/HO manifolds and 2 1/2 in. exhaust with x pipe. My car is a factory dual exhaust car and has the standard rear valance not the notched one like the GTO. Now the questions. Will the pY systems fit with no modifications? And what kind of horsepower gain can I expect? Thanks

[car guy]

I am doing some work to my 71 Lemans Sport Conv. this winter. Basically detail the engine compartment. While I was at it I thought it would be a good time to update my exhaust system. What I have is a bone stock numbers matching car with the 400 4 speed. I want to use D port RA/HO manifolds and 2 1/2 in. exhaust with x pipe. My car is a factory dual exhaust car and has the standard rear valance not the notched one like the GTO. Now the questions. Will the pY systems fit with no modifications? And what kind of horsepower gain can I expect? Thanks

[Ccass]

The system will physically fit if you are not looking for correctness as far as judging is concerned. Not sure what motor you have there as a lemans with 4 speed and 4 bbl is pretty rare. Adding a 2 1/2" exhaust to your combination might net you 10-20 hp because the car is totally stock. Most of that hp will be accomplished by the RA manifolds and mandrel bent downpipes. Not a big increase, But it sure will sound good!

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Fool around, Get hurt, don't come crying to me.

[Blackcat]

Make sure that you have 6 bolt holes in your heads on each side. Most 71-72's have only the center 4 bolts drilled and tapped.
If not you can use the header kit from Spot's or whoever has them.

Usually I'm found working on my Pontiac. If you want to find me Look for the white picket fence and all the old Pontiacs parked outside. And the half dissembled engine sprawled all over the driveway!

[car guy]

Ccass thanks for the reply. My car is very rare it has the same drive train that the GTO had for 71. I have it narrowed to one of less than 59 Lemans Sport conv. built that way. That is why I want to be sure I dont have to make any modifications. What is the deal with the bolt holes? Do the R/A's have six holes? Blackcat mentions a header kit, would this be required and what does it consist of? Thanks

[Blackcat]

The isue is that you really need to have the 6 bolt holes in your heads for the HO Exhaust manifolds to work. 71 and 72 Stock heads have the End bolt holes missing.
HO Exhaust uses the ends for mounting.
There is a kit out that may work. It consists of a braket with a stud that will enable you to mount headers to your 71-72 heads

Usually I'm found working on my Pontiac. If you want to find me Look for the white picket fence and all the old Pontiacs parked outside. And the half dissembled engine sprawled all over the driveway!

[car guy]

Thanks for that info. I guess the r/a manifolds are out for me. I would have liked to had them but have never been fond of adaptors. Im afraid they wont work well enough.

[ray t]

High Performance Pontiac just ran an article 2 months back comparing stock manifolds, heddman shorties, heddman full headers, PY RA/HO and RARE RA/HO manifolds. Good comparison. Might want to check it out...don't know if it's posted on HPP website. R

[chief455]

Car Guy : A 71 car with a factory 400/4 barrel should have cast number 96 heads. These heads have all the manifold mounting holes drilled and tapped. You can put HO manifols on that car and use a system from PYPES If you really have to have it original, and it came with "log" style manifolds than so be it. HO manifolds and 2.5" exhaust is more fun to drive by far though.