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Question: intake manifold gasket

Bolisk

Well-known member
Joined
Nov 2, 2007
Messages
441
Location
Crystal Lake IL
Corvette
1972 LS5 Convertible PS, PB, A/C
I have had my heads recently rebuilt (story in another thread), I have checked the new seals and they appear to be correct. I believe that I'm still having a intake Manifold Gasket sealing problem. . .and oil is being sucked into my intake from the lifer valey.

I have been using the Fel-pro stock replacement intake gasket (the one you get at pep boys, autozone. . .etc. . .etc.) which is BLUE in color. I dont' know the part nubmer. . . I do know that it's .060 thick.

Can anyone recommed a thicker intake gasket that may fix my oil sucking problem? Brand / part numbers would REALLY help.

BTW: I live in Illinois, so having the open heat riser for the choke would be a big pluss bit is not nesseacry at this point. I just want the buring oil to STOP!!!

-Bolisk
 
Once you get the intake off and everything cleaned up, set the intake on without gaskets and see what it looks like. Maybe use a .005 feeler gauge on both sides and see if it's setting flat against the heads. If the block was decked or the heads surfaced or milled at some time during their life, the intake may not be setting correctly.
 
Once you get the intake off and everything cleaned up, set the intake on without gaskets and see what it looks like. Maybe use a .005 feeler gauge on both sides and see if it's setting flat against the heads. If the block was decked or the heads surfaced or milled at some time during their life, the intake may not be setting correctly.
This was also my first thought. That the intake and head mating surfaces may not be parallel. Possible that somewhere down the line, someone, for some reason changed the height/angle of either. :ugh
 
I swapped out my intakes last weekend. I used Fel-Pro 1205 in place of the 1256 I had in there. All I really wanted to do was check for oil leakage and test the Hylomar. No leakage, the Hylomar is like contact cement, I was told it stays jelly like but this stuff setup in a few minutes and stuck good. I suppose it's like High Tach or Gasgonich? I used Ultra Black on the china walls and let it all setup 24 hours. Test fit the intake on the engine and had a gap over the walls and maybe 010-020 gap on the side rails. The 060" gaskets filled in nicely.
 
I have had my heads recently rebuilt (story in another thread), I have checked the new seals and they appear to be correct. I believe that I'm still having a intake Manifold Gasket sealing problem. . .and oil is being sucked into my intake from the lifer valey.

I have been using the Fel-pro stock replacement intake gasket (the one you get at pep boys, autozone. . .etc. . .etc.) which is BLUE in color. I dont' know the part nubmer. . . I do know that it's .060 thick.

Can anyone recommed a thicker intake gasket that may fix my oil sucking problem? Brand / part numbers would REALLY help.

BTW: I live in Illinois, so having the open heat riser for the choke would be a big pluss bit is not nesseacry at this point. I just want the buring oil to STOP!!!

-Bolisk

If they surfaced your heads when they rebuilt them (which is pretty common practice in commercial shops to avoid "comebacks" for head gasket issues) and didn't take the corresponding cuts on your intake manifold, you may have a sliver of an intake port (like #1) exposed to the lifter valley due to port misalignment. Chart below shows the standard metal removal amounts to maintain port and bolt hole alignment.


IntakeMachining.jpg
 
UPDATE:

So I've been driving arround for several months with the car still smoking. While it doesn't seem to be as bad as it was (amount of smoke) it's now smoking from both pipes. So back to the drawing board.

Last night I took the intake off. While I was cleaning the mating surfaces, I noticed that there was some charred oil burn marks on the bottom of the intake. I didn't think anyting of it at the time. This AM I took the intake to the machine shop to have the intake "shaved" to off set the amount that was removed from the heads when I had them rebuilt. The guy at the machine shop was very kind and said that before he did anything, he wanted me to borrow a tool (a feld pro gague) that would check the alightment of the heads to one another. . .in order to ensure that the heads were not milled off square. Before I did so, he checked the intake manifold itself. . .with the same gauge and showed me that the intake manifold as it was was correct surface and angle wise. Next he asked me how much clearance I had at the front and back on the china walls. After giving him my numbers he said that a surfacing was not needed unless the heads were out of whack angle wise. At that moment I didn't want to argue so I left his shop and when home to check the angles of the heads. When I droped the tool in, they were dead correct. Maybe .003 of clearance at the very top of ports (Away form the valley). I reported to the machine shop about what I had found and he said that the heads were will with in spec so they were not the problem. Next he told me that what they usually do, rather that shave the intake) is elongate the bolt holes slightly to ensure that he intake, when torqued down, does not catch on the bolts themselves. This seemed like a logical and reasonable solution to my potential problem. . .especailly after verifity that the last gasketes I used were compressing evenly and correctly (as far as I could tell). So I had him elongate the bolt holes.

After about 3 hours he called me to say that the intake was done. . .but that he had a question. He asked me if I planned to replace the oil shield on the bottom of my intake manifold.

My immediate responce was, "what the hell are you talking about!"

He then proceeded to fill me in on what was missing off the bottom of my intake manifold, and mentioned that there was clearly burnt oil on the bottom of my intake manifold where the heat riser cross over was. He then explained that this could be the cause of the smoking. . .if it was burning on the bottom of the manifold, then being sucked through the PCV valvue into the carb and out the exhaust. Because my smoking problem only starts after about 5 to 10 minutes after the care is started (after the exhaust is good and hot) this started to sound like a even more plauseable explination. Then it occured to me that the reason why my car may not have smoked before was because the heat riser passages were blocked off before. . .so the intake never really got hot.

At any rate, my intake (for as long as I have owned the car) did not have the splash shield on the bottom. So he had one lieing arround and I asked him to install it on my intake.

So, tonight I reassebled my engine, this time using the Fel Prol 1205 intake gasket. I cut a small hole in the gasket for the heat riser, because I do actually want that to work the choke. Not sure if that was a good idea. . .but I guess I will find out. I also did not use hi-take anywhere except arround the coolant ports. So everything is reassembled and the Right Stuff is cureing on the china walls.

Tommrow AM, I will fire her up and see what she does. I have my fingers crossed that this will solve the problem.

If this doesn't work. . .then it's either bad "new" valvue guide seals. . .or it's rings. . .

I will update tommrow.

Wish me luck!
 
On first fireing, it started smoking right on schedule, approx 5 to 10 minutes after starting. then after about 20 minutes. . .after i was done burping the radiator....i noticed that it wasn't smoking any more at idle. however it does puf a tiny bit when i start it and when i blip the throttel to full and off at idle. so there is a marked improvement. . . but not completely solved.

now the next problem is. i don't know what made the difference. here is what changed:

1) oil shield on back of intake
2) elongated bolt holes on intake
3) fel pro 1205 intake gasket (pintoseal)
4) Mobile 1 15w50 oil (up from 10w30)

the reason i switched to 15w50, is because that is mobile's offical recomendation for flat tappet lifters. it's a bit thick, but has a ton of zinc and phos

comments? opinions?
 

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