1957 Yblock intake manifold, rough idle

bobioknight

bobioknight

Member
I had a small water leak in my intake manifold, I replaced the gaskets, But now my engine idles high (1000rpm) and rough, coughs when I shut it off. I sprayed carb cleaner on all the fittings looking for leaks and found one fitting on the back of the manifold (running to the brake and fuel pump) next to the distributor was a bit loose, so I tightened it and it did not help.

Prior to gasket replacement it would idle at 550rpm smooth and ran nice, except for hard starts after running a while and it was warm.

Should I assume it is the gaskets and try to reinstall again? I cant get the carb cleaner underneath the intake to test the underside for leaks...

So I am stuck, any thoughts would be greatly appreciated.
 
Never used carb cleaner to check for vacuum leaks, always a bottle of propane with a rubber hose. The gaskets get my vote for a vacuum leak problem, but what heads are you running on the y block? The 57 intake really needs 57 and up heads to seal well, otherwise you really need to get out the gasketmaker for each port.

If it was running just fine before you changed gaskets, that has to be top on your list for the problem.
 
My worry was that everything seated properly, Slowly tightening and jiggling as it went down, The angle made it difficult to tell. When I test with propane, (except for fire) what should I expect to hear or see if I get close to a leak?

It is the stock, engine and manifold.
 
darrell said:
you probably put the intake gasket on wrong and its only running on 4
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What? IF it was on incorrectly it would be puking water all over the place. :rolleyes::rolleyes:

Listen to The Rev. Vacuum leak. I use one of those little butane torches (unlit). When you get where your leak is, your engine RPM will increase.
 
Intake gaskets put on wrong...
 

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Pretty funny, NO everything lined up... But using brake cleaner this time easily found the leaks. I just backed off the bolts and retightened them from the front to back... No more leaks. And found leaks under the carb, changed the gaskets as well and no more leaks there either... Runs better than ever now with a nice purring idle.
 
I've seen those gaskets installed on the wrong sides so it can be done. If the original center studs are not there, then the gaskets can slip down during their installation. I prefer white grease on the intake gaskets in lieu of gasket sealer. Ted Eaton.
 
I developed leaks again, seems like everything is good until I hit the freeway, 30 minutes or so I start feeling small amounts of stumbling, getting off the freeway idle is rough and very hard to start. Often I smell fuel like its flooding. I loosen the intake, retorque in a crisis cross pattern, it runs great until the cycle starts again.

It is obvious I have not torqued the bolts correctly, and I really want to do it right this time.

You mentioned center out... I Found in the manual the only thing it says is: 23 - 28 lbs or torque, working your way out from center to the ends.

So does that mean instead of crisscross pattern like I did, should I completely torque the passenger side of the intake then torque the drivers side. And obviously they did not RTV back in the day, and I read some people say yes and others say no, well I am not experienced enough to have formed an opinion, I am still feeling that I should use it lightly around the coolant ports. What say you?
 
bobioknight said:
... I loosen the intake, retorque in a crisis cross pattern, it runs great until the cycle starts again. ....
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Once gaskets have failed re-torquing won't fix them, they should be replaced.

Don't tighten one side then the other, the manifold may shift slightly off-center and put uneven stress on something.

Most recently I used a a thin layer of sealant on both sides of the gaskets and went around starting from the center out in a criss-cross pattern and ending with the two(smallest) bolts at the front.
'Just snug' all around to start with then again at 10ft lbs, increasing 5ft lbs each time til I got to 28.

Are there good split-ring lock washers on all the bolts?

TedEaton said:
I prefer white grease on the intake gaskets in lieu of gasket sealer.
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I missed this the first time around. A good idea. It would make replacing the gaskets easier the next time. Less scraping & cleaning crunchy sealer chunks out of the intake ports.

(edit)
Might it be possible you have a fuel delivery or carburetor problem and not just an intake leak?

>
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Check that the front valley cover bolt is not sticking up far enough to hit the manifold, preventing you from compressing the gasket. Usually when the bolt is not seated far enough, it results in breaking off one of the front ears of the manifold, but not always. John
 
Hoosier Hurricane said:
Check that the front valley cover bolt is not sticking up far enough to hit the manifold, preventing you from compressing the gasket. Usually when the bolt is not seated far enough, it results in breaking off one of the front ears of the manifold, but not always. John
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Yes. The one I just did needed the top half cut off the overly thick grommet for the front bolt, to let the intake manif sit down far enough.
 
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