Hi guys, I just picked up a nearly new full exhaust system w/ 3" midpipe for my 83 Firebird that will have a 305 TPI in it. Are any gaskets used between the manifolds and the exhaust pipe, or do they just mate up metal to metal and seal on the flange socket type connections? One manifold has a flange with the bulge that looks like it will directly mate to the exhaust headpipe and seal with no gasket involved. The other manifold has a flat flange, and then there is a removable cast iron piece that inserts against the flange. This has the bulge on the other end. Is there a gasket in between this piece and the manifold, or does this just bolt up as well?

 

The TPI manifolds have a 'ball' end which goes to the y-pipe inlet. The pass side has a 'spacer', flat on one end, 'ball' end on other. I just took mine apart. Mine had no gaskets anywhere, even on the flat-side of the spacer that mates to the flat outlet of the manifold on the pass side.

Before you install these manifolds, take a look inside at the ports where they bolt to the heads . Mine had lots of raised, blocked areas around the smog tube 'bosses'. This made things appear pretty restrictive. I ported / blended all these areas quite a bit, much as I dared. It really opened things up decent , as far as stock log manifolds go. Its not as good as headers, but it helps, and its a free mod!

 

Thanks 91, I suspected the manifolds didn't use any gaskets. I am building this car for my fiance to use as a local daily driver, performance is not really on the menu, so I won't be porting anything. The 305 TPI will move the car fast enough compared to the POS 2.8 I pulled from the car. The 2.8s in these cars are dangerously slow, I wouldn't put someone in the situation of having to make an emergency lane change with one.

 

- agreed, no gaskets, hell GM didn't even put gasket between the heads and the manifolds. - putting a TPI in place of a 2.8? good stuff, especially since it probably has 3.42 gears...although one wheel wonder...