GRAND PRIX 79 Grand Prix Resurrection

[CDUNIGAN1981]

So there are two different sized D port Pontiac heads?

I have not pulled my manifolds off yet so I dont know which size I need.

My header flange looks like Remflex 12-004. Im going to measure before I order.

Does any have any history on this?

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[CDUNIGAN1981]

Old exhaust is off
So is feeling in my right hand bc of a snapped swivel.

The snapped swivel sent me to Lowes. I bought an entire mechanics set. It was so much faster to have it all. Most of the tools I had were random. Full sockets and wrenches were overdue.

Curious to see how these headers fit.

Im getting pretty excited about this car again.

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[84GP455]

For the gaskets one says "D-shaped Center with Oval End Ports" and the other just says "D" port. There are only one size "D" port as far as I know, they are either round ports, pre-1970 (with the exception of the Ram Air heads) or "D" ports 1970-up. As far as header go, in my opinion they are not worth the hassle for 15-25 HP that you might gain from them. When I did my build I could not get any make headers to fit into my engine bay, the passengers side is ok but the drivers side they all hit on the steering column and A-arm, so you have to notch or bang them in with a hammer in order to fit. Plus my collector gaskets constantly leaked and they hang lower than factory headers of course, so when you go over a big speed bump they could hit and then bend the collector flange which happened to me a few times. I swapped to the factory headers like the ones you have there back about 20 years ago and never had to change a manifold gasket or had a leak. Headers in my opinion do not justify the 15-25 hp that you gain vs. the leaks and problems that I had with them.

 

[carnutjw]

Those are decent exhaust manifolds, whether original or reproduction. They are Ram Air models according to part numbers, the 9777642 and 9777646, 2.25" outlet originally, repros could be 2.5" or 3". My point is, don't throw them away. You might want them later or could sell them.

 

[carnutjw]

Oops, hadn't checked for sale thread until now.👍

 

[84GP455]

If those are Ram Air manifolds then they would be round ports, as all Ram Air heads were round port which are not interchangeable with D port manifolds. If he has 6X heads they are "D" port manifolds........ So they are Ram Air "reproduction" manifolds not factory, I see now.

 

[84GP455]

Since those are Ram Air "restoration" manifolds and they breathe better than factory "D" ports you might want to keep them over the headers. It's my opinion but headers are really a headache and these manifolds have been tested against headers in High Performance Pontiac magazine and they flowed better than headers.

 

[CDUNIGAN1981]

For the gaskets one says "D-shaped Center with Oval End Ports" and the other just says "D" port. There are only one size "D" port as far as I know, they are either round ports, pre-1970 (with the exception of the Ram Air heads) or "D" ports 1970-up. As far as header go, in my opinion they are not worth the hassle for 15-25 HP that you might gain from them. When I did my build I could not get any make headers to fit into my engine bay, the passengers side is ok but the drivers side they all hit on the steering column and A-arm, so you have to notch or bang them in with a hammer in order to fit. Plus my collector gaskets constantly leaked and they hang lower than factory headers of course, so when you go over a big speed bump they could hit and then bend the collector flange which happened to me a few times. I swapped to the factory headers like the ones you have there back about 20 years ago and never had to change a manifold gasket or had a leak. Headers in my opinion do not justify the 15-25 hp that you gain vs. the leaks and problems that I had with them.

Remflex 12-004 and 12-001 each have d ports in the middle and oval ports on the ends which is why Im confused.
Remflex 12-002 (I believe are the round ports) for SD and HO motors.


What kind of headers did you use?

 

[olds307 and 403]

Since those are Ram Air "restoration" manifolds and they breathe better than factory "D" ports you might want to keep them over the headers. It's my opinion but headers are really a headache and these manifolds have been tested against headers in High Performance Pontiac magazine and they flowed better than headers.

You guys are lucky. Full length headers on Olds V8's are worth 30 hp, maybe more if tuned with collectors. This is the "442/W30" high performance divided manifolds too. Our wide block leaves little room for manifolds especially on the shorter deck 260 through 403. Would not surprise me if it was more like 40 hp for the regular log manifolds. There has been 0 testing done on the Thornton manifolds and shorty headers, I wish someone would test them to see the gains.

 

[carnutjw]

If those are Ram Air manifolds then they would be round ports, as all Ram Air heads were round port which are not interchangeable with D port manifolds. If he has 6X heads they are "D" port manifolds........ So they are Ram Air "reproduction" manifolds not factory, I see now.

Negative Ghost Rider- Not all Ram Airs had round exhaust ports. As far as I know, the 1967-68 Ram Air and subsequent Ram Air III had D-ports. The 1968 Ram Air II, 1969-70 Ram Air IV, 71-72 455HO, and 73-74 455SD had round ports.