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Old 12-12-2013, 12:04 AM
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Oil leak under valve cover

I was running my truck at a pretty high idle, it has a 350 sbc, 1990. The valve cover bolts run through the center of the cylinder heads. The gasket I have is a blue rubber gasket that I picked up from Oreilly Auto Parts. Back to the explanation. I was running my truck at a pretty high idle in park to warm it up, and my dad tells me to kill the engine. I looked and saw that I had smoke coming off of my header, and that oil had sprayed from under the front right corner of my valve cover. I removed my bolts to my valve cover, they werent on very tight, meaning they could have been on tighter. I checked the valve cover gasket, which was still in good condition and had no cracks or splits. I think it was just the valve cover not being tightened all of the way, but I heard from a guy I work with that Chevy is known to have their valve covers with center bolts leak all around for no reason. Advice and or help please. Thanks

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Old 12-12-2013, 05:35 AM
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You may be experiencing a gasket shift due to bolts not being tight enough. Sometimes even if they are tight, with vibration from the motor they can shift.
I always use a good high temp silicone and adhere the gasket to the inside of the cover. That way it stays where you put it and it won't shift with vibration.
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Old 12-12-2013, 08:18 AM
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If it continues to leak after tightening to the proper torque,you covers could be warped.A lot of the cheaper chrome covers are thinner & warped when you buy them.Overtightening can also cause a leak.Another thought that comes to mind,is,ck your drainback holes in the head.Sometimes these can partially clog,causing slow drainback & leaks from the valvecover.A malfunction in the PCV system can also cause oil to blow from valvecovers.
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Old 12-12-2013, 09:52 AM
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Pull your PCV and shake it, if you hear it rattle like a spraypaint can, its supposed to be in good working order.
check your valve cover flanges, you may need to tap them flat again, make sure you support one side of the lip with something when you tap against it. If they're diecast, there really isnt a fix other than to use some sort of sealant between the cover and the gasket. do NOT put sealant on both sides of the gasket. Someone here should have a torque spec for centerbolt OEM valvecovers, but if you have stamped steel cheapies, I have no idea. Over-tightening them is just as bad as leaving them loose
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Old 12-12-2013, 12:12 PM
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Quote:
Originally Posted by 88scottsdale View Post
I was running my truck at a pretty high idle, it has a 350 sbc, 1990. The valve cover bolts run through the center of the cylinder heads. The gasket I have is a blue rubber gasket that I picked up from Oreilly Auto Parts. Back to the explanation. I was running my truck at a pretty high idle in park to warm it up, and my dad tells me to kill the engine. I looked and saw that I had smoke coming off of my header, and that oil had sprayed from under the front right corner of my valve cover. I removed my bolts to my valve cover, they werent on very tight, meaning they could have been on tighter. I checked the valve cover gasket, which was still in good condition and had no cracks or splits. I think it was just the valve cover not being tightened all of the way, but I heard from a guy I work with that Chevy is known to have their valve covers with center bolts leak all around for no reason. Advice and or help please. Thanks
The elastomer gasket when mounted is in a stretched condition, if the bolts are loose enough for the gasket to escape its retainer oil will leak from the gasketed surfaces. You may well find that you'll need to remove the cover from the engine and the gasket from the cover to reposiiton it. If the gasket proves to be short on lenght, you will need to hold the ends and stretch it over your chest like doing pectoral exercises with stretch bands to lengthen it to where it lies in position on the valve cover before reinstalling the cover. A little 3M adhesive can be helpful in keeping the gasket positioned on the cover. Work quickly as the stretch doesn't last too long, so you've got to get the cover bolted down to clamp the gasket in place.

Bogie
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Old 12-12-2013, 01:32 PM
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When ckn the PCV system'shaking the valve will tell you if the valve is working,however,you also need to verify that there is vacum present @ the valve.Ports in the intake can stop up blocking vacum to the valve.This in turn can cause oil leaks from too much crankcase psi.Hopefully repositioning & tightening will solve your problem.
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Old 12-15-2013, 08:41 AM
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I had a set of the cheap chrome center bolt valve covers,one had such a poor flange the gasket would not stay on the cover. Try to use the originals and tighten from the center out .
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1990, chevy 350, oil leak, truck, valve cover

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