Exhaust manifold leaks

[Stan W.]

I just replaced all the intake and exhaust gaskets on my 52 Special. I followed the tightening sequence in the shop manual but the exhaust ports in the center lay a little back from the head. Needles to say they are leaking. Can I just put another gasket between the head and exhaust manifold or is there another way to seal the gap? Thanks,

[brad54]

I don't know if that would work. Ask a muffler shop if they've got extra thick gaskets?<BR>I've heard of resto guys machining the exhaust manifold's mating surface, and the mating surface on the head, so both are perfectly flat again, then not needing gaskets. They didn't come with gaskets from the factory.<BR>That probably doesn't help you right now, but it may help others before they get it all bolted together.<BR>-Brad

[NTX5467]

There are a couple of options here.<P>The first might be to loosen the manifolds and then retorque the center bolts in sequence by themselves. Then do the outer bolts in sequence. Hopefully, getting the center ones done first might work around the situation.<P>The second option would be to get the manifolds "surfaced" on what I call the "rotating rock surfacer". This is how many older machine shops surfaced cylinder heads when having a lathe was too expensive or "fancy". Take off just enough metal to get a uniform surface and no more.<P>At that point, you can reinstall the manifolds and tighten in the specified manner.<P>The variation of this would be to also put a black header gasket set or the exhaust manifold gaskets that would come in an engine overhaul gasket set between the manifold and the head. Many engines that did not use exhaust manifold gaskets from the factory would have those gaskets in the overhaul sets, or available separately, from the gasket suppliers.<P>Also, be sure to put the correct fasteners back on with the manifold. If there were flat washers under the bolt heads, use them. If there were not any, I strongly recommend you find some that are just barely larger than the bolt head while still having the correct inner diameter. Still follow the factory torque procedures.<P>Washers, you say?? Yes, washers. As the manifold and engine heat and cool, the manifold will see greater heat variations than will the cylinder head. I suspect you'll also discover the bolt holes are a little bigger than they need to be. If a bare bolt head digs into the manifold and restricts it's "movement" as during the heat/cool cycles, the manifold can crack. Plus, the flat washer will allow a better interface during the torqueing process.<P>Sometimes, you can be sneaky and coax things along with the alternate torque procedure I mentioned first, but surfacing the exhaust manifold is a reasonably common deal too, but can't be done more than about once before the manifold bolt flanges could get too thin.<P>Just some thoughts . . .<BR>NTX5467

[Guest]

Read your factory bulletins to see how Buick handlrd the situation back in 1940.