[Dick Boneske]

I'm about to put the HO manifolds on my '64 GTO heads and have both the OEM metal gaskets and Fel-Pro fiber gaskets. The OEM metal gaskets do not have dividers between the center ports like the aftermarket ones have.

Any advice on which gaskets to use and whether to use any compound on either? I've can't remember ever having problems with the OEM metal gaskets leaking with cast manifolds--and I never used compound on them.

Also, with the Pypes 2 1/2" downpipes, the flares are too large for the three-bolt pattern on the HO manifolds. Removing about 3/32" from the OD of the flares would allow clearance so the studs would fit into the manifolds. What would be the easiest way to remove 3/32" from the OD of the flares? I've considered a disc sander, belt sander or 4" angle grinder. Marking the area to be removed with magic marker would help avoid removing too much material. The flares will still seal with the material removed--there's twice the material needed in the flared area.

[b-man]

I used OEM metal gaskets with no sealer for the manifold to the head, I see the missing divider in the gasket as a non-issue. The steel shim gasket is so thin that not much gas can pass, the manifolds are not a tuned header in any sense so some leakage here doesn't make any difference. The dividers usually burn out quickly anyway on fiber gaskets.

Use whatever tool or method that seems to work best for you to take the flare diameter down, keeping control of material removal is more important than speed of the operation.

No need for any sealer at the pipe to manifold joint, just be prepared to retorque the bolts several times as the pipe flares take a 'set' to the manifold sealing surfaces.

I had a set of '67 RA manifolds on the 455 in my '64 Tempest for 30K miles before selling them, at the time I figured I was done with them as I had a set of round-port Tri-Ys and planned to use Edelbrock heads later on. Have since moved on to a new LS3 GM crate engine with that car, but that's another story.

[66Post]

Felpro OEM type metal gaskets used on my 66 with RA manifolds on "093" heads, no issues.

[Dick Boneske]

Thanks for the feedback. I will go with the OEM metal gaskets.

[Dick Boneske]

I learned tonight that the outlet ID of the OEM '67 HO exhaust manifold is almost exactly the same as a 2 1/2" downpipe--about 2.3". I had been told by several people that the factory HO manifolds shouldn't be used with 2 1/2" pipes because the outlet is too small and would be the same as running 2 1/4" pipes all the way back. Not true!!

The 2 1/2" pipe, however, barely fits within the 3- bolt circle at the manifold outlet. It will be difficult to tighten the nuts on the studs as a socket won't fit on all of them--just some.

[b-man]

Here are some pics of my old manifolds and downpipes that I sold.

I started out making the downpipes using some 2-1/4" tube stubs that I had a muffler shop expand to 2-3/8". I then flared both ends using a piece of tapered spinning tooling we had laying around at work and a large arbor press, I had to install the flanges before making the bottom flare.

I then mated the stubs to some 2-1/2 pipe that I had bent at the muffler shop. I first installed the stubs on the manifolds (engine and manifolds already installed in the car) and then fitted each pipe to get the ground clearance needed before the final welding.