The Stovebolt Site Forums The Shop Area Engine Shop intake/exhaust mainfold won't tighten up flush to head

I'm trying to bolt my engine (and entire truck) back together after having the engine rebuilt. It's a 1959 235 ci . My manifold was broken so I bought one from someone through the parts for sale on stovebolt. I completely cleaned and disassembled the two halves of the original style manifold but I noticed before taking it apart that the intake and exhaust ports were not in line very well. I anticipated that separating the two halves and having the two halves loosely put together while tightening the manifold to the head might help this trouble but after assembling and tightening from the inside outward on the bolts, the intake ports are fitting very tight and the exhaust ports need to be tighter since I can push a .015 feeler gauge into the exhaust ports without placing much effort to do so. Has anyone ever used two manifold gaskets on exhaust ports and one on the intake? Just wondering what to do besides spending a lot more money on this thing?

If you take the manifolds off and lay a straight edge on the gasket surface chances are you will find that its warped. If so it doesn't usually cost to much to have the gasket area re-surfaced. Using multiple gaskets usually don't hold up well.

Always make sure that both manifolds are bolted together when machining is done. This will correct a warped and out of plane issue, between the manifolds.

Joe

It is common for inliner manifolds to be warped. I just bite the bullet and take them to a machine and have them straightened on a belt sander. It saves a lot of headaches.

Milling is my preferred method and as long as warpage is 1/32" or less the exhaust manifold can be machined separately which is also much easier to clamp. See here. Belt sanding is hit and miss IMO.

I am a firm believer in having the intake and exhaust bolted together in their final position. I have been truing them as a unit on a belt sander for 50 years and haven't missed one yet. I have seen the intake and exhaust milled separately only to discover that the mating surface of the two manifolds was warped and the guy who spent money to have them milled separately still had leaks. I also have fears of milling 60 year old cast iron. I have seen it shatter.

My machinist made me take them back (an hour each way) and install them on the engine and secure them heat box then bring them back as Crenwelge says. I think he muttered something bout a waste of time otherwise. Hmm he'd been doing it for 50 years too...
It made sense when I thought about it.