[mfearer]

Hello, fellow GP'ers. I have a 1971 J with a 400 and '99' Poncho heads
that are connected to Hedman headers. I may be wrong, but to the best of
my knowledge, Hedman is the only outfit that makes headers that will fit a
1971 GP out of the box.
My dilema; I want to put on Edelbrock Performer RPM Pontiac aluminum
heads. These heads are designed after the legendary Ram Air IV, thus they
*say* that they require Ram Air IV headers. G-T-O? Firebird? No problem.
But my neighborhood speed shop is having a tough time trying to come up
with a set of headers that will work/fit into my GP that will properly
connect to the Edelbrock heads.
Has anyone else had success with Edelbrock Performer aluminum heads on a
400 in a '71 (or '69, '70, or '72)?

------------------
Mark Fearer

[mfearer]

Hello, fellow GP'ers. I have a 1971 J with a 400 and '99' Poncho heads
that are connected to Hedman headers. I may be wrong, but to the best of
my knowledge, Hedman is the only outfit that makes headers that will fit a
1971 GP out of the box.
My dilema; I want to put on Edelbrock Performer RPM Pontiac aluminum
heads. These heads are designed after the legendary Ram Air IV, thus they
*say* that they require Ram Air IV headers. G-T-O? Firebird? No problem.
But my neighborhood speed shop is having a tough time trying to come up
with a set of headers that will work/fit into my GP that will properly
connect to the Edelbrock heads.
Has anyone else had success with Edelbrock Performer aluminum heads on a
400 in a '71 (or '69, '70, or '72)?

------------------
Mark Fearer

[GP-K]

Mark,

Since GP's never came with round port heads, you have limited choices. Manufacturers do not make a good selection of off the shelf round port headers for the 3rd gen GP's. Your best choice in headers would be a custom header, designed for the chassis and application. (You have spent nearly 2k on a pair of cylinder heads, 1,000 for a good set of headers would probably be a good investment).

Another option you might entertain would be obtaining a set of 1st gen F body round port exhaust manifolds. They look the same as the 428 HO manifolds, but would fit the E-heads. You would not develop as much power as a set of custom headers, but your power and torque would still be in the neighborhood of an inexpensive set of mass produced headers.

This is a question I also face in my plans for my E-headed 428 HO (in my '69 SJ). I have been leaning in the manifold direction because of the "sleeper" potential, but a carefully done set of custom headers with a ceramic plasma spray coating and thick flanges sounds pretty good too.

On a side note, I have used Heddman headers on my GP years ago, and found them problematic. The three tube design was little better (if at all) than the HO manifolds, and I had to disconnect the steering column link to the transmission. In addition, my ground clearance was negatively effected too. I am pretty sure that the header Heddman lists for the GP is a multi-fit design, and they just happened to find out that it could fit the GP. I just don't think that they made (or currently maintain) a jig just for the GP.

Just a couple of thoughts.

K.

[This message has been edited by GP-K (edited 09-23-2000).]

['ol Pinion head]

GPK, have you seen a set of 4 tube D-Port headers in a '69-72 GP? I am figuring they would be for a 68-72 Lemans GP application, as the '69-72 GP had it's engine moved back & the frame is stretched 4" behind the frame turndown & in front of the main (side) frame rail.what would be in the way? Just wondering if the '68-72 4 tube D-port headers would fit, then possibly the '68-72 roundport headers would work with the the e-heads in this chassis.

[GP-K]

OPH,

At least for '69, the GP engine mounts and under engine crossmember are significantly different than the A body. The GP engine sits about 1" lower in the chassis than it does in the A body because of this difference in engine mounting. I just seem to remember that many headers which do "fit" the A bodies will not fit the GP. Just not really sure why other than the mounts & xmember.

Why didn't they use the RAIII manifolds on the GP? another question I really just don't have any answer for. Maybe John Z. or Jim W. might know.

I would have to go out and buy several sets of A body headers and test fit them with the GP. Who knows?

K.

['ol Pinion head]

GPK, I will try to hustle up some used 4 tube 68-72 A-body headers & install them & an engine in one of my extra GP frames. All '68-72 D-port headers, I have at this time are universal 3 tubes, so need to borrow some 4 tubes. I have always figured that Pontiac used the long branches in the '69 GP's because of the expanse of room in the rear due to the stretched frames. This expanse of room is why I made some assumptions in my earlier post. Figured it would make a good discussion as we both have a lot of GP experience. I agree that the roundport longbranches would be cool but super $$$, lot more than a set of modified & tweaked '68-72 roundports. Just hoping that maybe no mods would be needed to these 68-72 headers.

[mike nixon]

oph, post your results as i will definietly be interested in your findings. the last set i installed on a g-body were a major pain. mike

[Rocco Testa]

Back in the early 70's I owned a 65 2+2 376 HP Tri Power that I just had blueprinted.I always hung out at Nuniz's Auto and worked there from time to time at the shop.He always use to tease me about the SD manifolds he had, that they would fit right in the car without any mods done to the car, but there not for sale.Then we had a set of 68-69 GTO headers with power streeting laying around and we tried them on when he wasn't to busy. Guess what they fit in like they were made for the car.I just had to make a little ding to clear my power steering and the car was a 4 speed.Now I don't know if a 69 or 70 GP uses the same chassis as the Big cats, but I though this may help you in some. As the RA IV should be in the same place as a D port head is.By the way the header was a Hooker.

[This message has been edited by Rocco Testa (edited 10-01-2000).]