Had an annoying snick-snick barely audible and traced it down w/ a smoke test to the exhaust manifold at the top of the #7 exhaust port. The PO had installed gaskets, and it looks like either the gasket failed, the surface is too pitted, or both. I don't have practical experience to judge if this surface is too pitted to do without a gasket, or if it is likely to seal to the block as is. What do you think? If experienced eyes say it is likely to cause problems I can bring it to a local machine shop and have it cleaned up. I have gaskets but would rather not use them.

The block looks great, it is just the manifold surface that has pitting.

Thanks.

 

I would say that is not good enough to use without a gasket. The "pitting" actually looks like it was from one of those perforated metal gaskets being used.

People dont realize how really difficult it is to resurface exhaust manifolds. I dont even try. There is no good way to get them clamped in the modern type of milling machine most machine shops have. You need to ask around and see if you can find a shop with one of the big belt sander type machines. That is really the only way to surface one. Maybe if someone in your area has an ancient Van Norman broach. They will work most of the time but its still a pain to set it up.

I agree with you that the preferred way is without the gaskets but sometimes you dont have much choice and truthfully there are probably a bazillion cars out there with gaskets and not many issues.

 

When these engines came from the factory, everything was flat and square. Through thousands of heating and cooling cycles, internal stresses came into the picture and changed shape. This is called warp. The exhaust manifold side of the head is no longer flat, nor is the exhaust manifold. Ever wonder why heads are resurfaced on the head gasket surface ?

As BillK says, people don't realize how difficult it is to resurface exhaust manifolds. There is no good way to clamp them without some machining. I re-machined an exhaust manifold to true up a broken bolt ear.enough for a gasket. The whole manifold surface was flat within .012"

A big belt sander will smooth it up, but don't count on it making the surface flat.

 

The type I mentioned absolutely will get it flat. But not many people have them. There is a guy local to me with a Heavy Duty truck shop. He has one and that is who I send people to.

https://www.comecpn.com/en/engine-li...elt-resurfacer

 

My buddy happens to have a big belt sander (maybe 2', on a bench) in his garage. I took my manifolds off and took them over. I just sat the manifold on the belt and held it as belt turned. I could see high spots. I just went until it all looked flat. Takes a long time and very dirty- lots of "Iron dust" all over me and floor. I put back together with gaskets- sounds good.

 

JUST a thought, I have taking exh manifolds to my local machine shop and they do a great job. If you have a machine shop around you see if they would take care of this...They use a milling machine. same as the cylinder heads..I don't know how they secure this to do it,,,, but they do...

 

That wouldn't be too hard to custom fixture. Expensive, though.

 

Cost me 130.00 FOR 2 USUALLY, some a bit more. Sure beets me trying to true them up.

 

Quick anecdotal story: I had an 02 Silverado with a cracked manifold. Took the "good" side to get surfaced= $80 at the machine shop. New Dorman manifold to replace the cracked =$50.

Get a quote, weigh your options, then get some Remflex gaskets.

 

I don't know if you could find a reman manifold for this car or not, all newer and popular cars that is the way to go for sure. I agree with you 100%
maybe he wants to keep this a number matching ???

 

What's wrong with using high temp 700° silicon gasket ?

 

Actually, I didn't even think of it - I assumed there wasn't a gasket material made for direct contact w/ the heads at the exhaust ports. After your question though, I'd rather not just because future me will hate current me when he has to pull the glued on manifold and clean it all off the heads the next time I have to remove it (for whatever reason).

 

Just want to make an educational comment.

A lot of people don't realize that one of the reasons that most manufacturers do not use gaskets between cast iron manifolds and the head is for heat transfer. When the manifold is mounted right to the head without a gasket the heat from that manifold can get transferred to the head and dissipated by the cooling system. When you put a gasket in between the manifold temperature goes way up. Then the manifold expands and contracts and the gaskets don't last Worst case and the manifold cracks. I dont know if it is a big issue with Oldsmobile but it is critical with a lot of engines.

So if there was no gasket from the factory, it it always best to put it back the same way if at all possible.

 

You could hit it with a sander but MAW use a good quality gasket.