oil on intake valve's back - sbc

Belgian1979vette

Belgian1979vette

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I took off my intake manifold today in preparation of the EFI install. Found out that some of the closed intake valves have some slight amount of oil on the back of them. Car sat for 2 weeks prior to disassembly.

New heads, new seals (viton ones). Engine has about 1000 miles.

Is this normal or are the seals already shot ?
 
Funny you ask, but yes there is some oil on the bottom part of the intake gaskets. Would it be sucking air + oil through the intake gaskets ?
 
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no sealer on the rocker studs will do that also on heads that have the threads all the way through to the intake runners
 
Twin_Turbo said:
no sealer on the rocker studs will do that also on heads that have the threads all the way through to the intake runners
Click to expand...

I anticipated that one and did put sealant on the threads. I think that the intake gaskets weren't sealing correctly. I was low on vacuum so I might have found the source. Will put a good amount of sealer on it this time.
 
Belgian1979vette said:
Twin_Turbo said:
no sealer on the rocker studs will do that also on heads that have the threads all the way through to the intake runners
Click to expand...

I anticipated that one and did put sealant on the threads. I think that the intake gaskets weren't sealing correctly. I was low on vacuum so I might have found the source. Will put a good amount of sealer on it this time.
Click to expand...

Yeh, I learned that the same hard way a few years ago, with no lifter pan the oil is free to suck into the passages, so I put on a film of RTV on the lower edges, seems happy enough.....obviously I let it set up until the next day before starting.....

:smash::surrender:
 
Yes and no, I checked the clearance between the manifold and heads with some play dough and some pieces of old gaskets to get it to the right height. Turns out that the bottom of the face has 0.065-0.070 clearance and the top 0.055-0.060. Gasket is a 0.060 type.

I think I'm going to use the 0.120 gasket since sealant doesn't really hold up to gas. A bit worried about the distributor ending up at the wrong height though.

Suppose this was all cause by decking the block and cleaning up the head surface.
 
Decking the block should not change that intake angle, but sometimes they mill the heads at an angle and that definitely opens up the bottom edge.....

Maybe any possibility to knock 5 mills off the top edge on the intake, ??? change the flange angle?? I would think it not to drop down in the valley too much but give you some advantage on sealing that bottom edge....

:eek:
 
I don't like the idea of milling the intake. That makes it engine specific...

I think that with a thicker gasket I would be able to compress it more so that it closes all around.
 
mrvette said:
Belgian1979vette said:
I don't like the idea of milling the intake. That makes it engine specific...

I think that with a thicker gasket I would be able to compress it more so that it closes all around.
Click to expand...

I hear you, best of luck, hope it works out....:smash::thumbs:
Click to expand...

Remember this is not some off the shelf intake. It's an ITB manifold. Difficult to get and expensive. Anyway the surfaces of the manifold are straight as are those of the heads. I assume they shaved more off the block on the intake side than the exhaust side when they decked it. Will try to find some permatex aviation sealant. It seems like it is gasoline resistant.
 
There are pros and cons to all of the solutions: if you use the .120" thick gaskets you need a lot of RTV at the front and rear (intake will sit higher), the distributor may end up too high (as you said)....

If you seal off the ports and the block you could just take the .010" off the heads - at the intake flange surface ... that way any intake will fit with standard gaskets, basically restore the intake flange angle to what it's supposed to be....
 
Belgian1979vette said:
Yes and no, I checked the clearance between the manifold and heads with some play dough and some pieces of old gaskets to get it to the right height. Turns out that the bottom of the face has 0.065-0.070 clearance and the top 0.055-0.060. Gasket is a 0.060 type.

I think I'm going to use the 0.120 gasket since sealant doesn't really hold up to gas. A bit worried about the distributor ending up at the wrong height though.

Suppose this was all cause by decking the block and cleaning up the head surface.
Click to expand...

Mhmmmm..... this is the problem !

By the way 0.01" isn't that much and a thicker gasket may solve the issue.

An othe option are the gaskets with a very small clamp force with silicone bead, like these:
http://www.summitracing.com/dom/parts/sce-211102/overview/make/chevrolet
 
Stroker-427 said:
Belgian1979vette said:
Yes and no, I checked the clearance between the manifold and heads with some play dough and some pieces of old gaskets to get it to the right height. Turns out that the bottom of the face has 0.065-0.070 clearance and the top 0.055-0.060. Gasket is a 0.060 type.

I think I'm going to use the 0.120 gasket since sealant doesn't really hold up to gas. A bit worried about the distributor ending up at the wrong height though.

Suppose this was all cause by decking the block and cleaning up the head surface.
Click to expand...

Mhmmmm..... this is the problem !

By the way 0.01" isn't that much and a thicker gasket may solve the issue.

An othe option are the gaskets with a very small clamp force with silicone bead, like these:
http://www.summitracing.com/dom/parts/sce-211102/overview/make/chevrolet
Click to expand...

I think he means .055"-.060" vs .065"-.070" which is a .010" difference (0.254mm)

Damn metric system ... Lol..... :smash::smash:
 
MYBAD79 said:
There are pros and cons to all of the solutions: if you use the .120" thick gaskets you need a lot of RTV at the front and rear (intake will sit higher), the distributor may end up too high (as you said)....

If you seal off the ports and the block you could just take the .010" off the heads - at the intake flange surface ... that way any intake will fit with standard gaskets, basically restore the intake flange angle to what it's supposed to be....
Click to expand...

The chinese wall of the block hasn't been milled (although I requested it). Gap is already rather thin, so this will not make it any more problematic in that area. And I already use RTV at that area.

I made some preliminary checks with the distributor and 2 stacked gaskets and it seems to be ok.

I already mad the order for the Felpro gaskets.

I think the main problem arises from the fact the gaskets are only 0.060 thick. So this leaves only minimal clamping at the bottom edg where there is a 0.010 difference with the top.

The SCE's are not available in my port size so it seems.
 
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