Manifolds

Tom F OHIO

Tom F OHIO

Well-known member
I got a new exhaust and intake manifold. Before I bolt the two together do I need a gasket between where they bolt together. Also is there a
pounds for the two bolts or do you tighten them until you feel they are
tight.

Thanks,
 
There is no gasket between the manifolds. You just need pinch up the bolts, and use spring washers. After bolting the two together, run a straight edge along the faces that mount to the engine to make sure they will sit flat, as well as along the bottom, or top of the ports to ensure alignment along the manifold.
 
To ensure they are level, I use a piece of Glass. I use glass to lay my motorcycle valve covers on to ensure they are flat and don't leak oil. The glass works for the bikes, and works for the head. IMHO
 
I replaced the exhaust manifold and bolted them down with the 2 bolts loose, then noticed there was about a 20 thousands gap where they bolt together, used some shim stock from a chevy starter, cut the right size and tightened it down. Not that's the way to do it, but worked for me.
 
I ran the bolts between the intake and exhaust manifold hard finger tight, (no shim between the manifolds) then used a straightedge to line up the average of the exhaust and intake openings, moving the intake manifold to get the best alignment

Then I tightened the bolts gradually in several stages to "gut feeling tight" while re-checking the alignment of the holes.

Then I checked the flatness of the intake and exhaust faces using a flat surface stone, and of course, they did not align.

At this stage the purist solution would be to use a professional surface grinding machine.

However, I simply taped a large piece of emery cloth (180 grit i think) to the flat surface stone and sanded the whole manifold face assembly until all areas around the intake / exhaust openings had been touched by the emery cloth. You need to take great care that you press the manifold assembly face evenly against the emery cloth, and that you keep away from where the tape fastens the emery cloth to the flat surface.

This brought my assembly flatness below 5/1000.

It is probably easier to hold the assembly evenly against the surface while sanding if the exhaust ports stick further out than the intakes (like in my case) If the intake ports stick out beyond the exhaust, you may want to give the intake a go on the cloth alone before proceeding with the assembly

Now lets hope that your block is straight !
 
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