Predator 420 head gasket
- Thread starter Rgreif21
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BrownStainRacing
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Welcome!!!
How thick is the gasket???
On small blocks with the thin shim gaskets, I put flat washers under the head bolts, and use copper gasket spray on the head gaskets, usally 5-10 thin coats.
Some blocks, the bolts will bottom out with the thinner gaskets and not seal.
I do the same with studs.
Another thing, is too much crankcase pressure on older, used engines. 1 way check valves will solve that problem, if engine is not completely worn out.
How thick is the gasket???
On small blocks with the thin shim gaskets, I put flat washers under the head bolts, and use copper gasket spray on the head gaskets, usally 5-10 thin coats.
Some blocks, the bolts will bottom out with the thinner gaskets and not seal.
I do the same with studs.
Another thing, is too much crankcase pressure on older, used engines. 1 way check valves will solve that problem, if engine is not completely worn out.
I have this gasket on now https://www.nrracing.com/product-p/hgc45-90.htm and what is a check valve
Denny
Canned Monster
Permatex aviation head gasket sealer.
BrownStainRacing
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That's a thick fiber gasket. Should have been fine, I don't see a fire ring tho.
1 way check valves, I use em to replace the stock baffle in the valve cover. They let pressure out, but dont allow air back in. We can get to those later.
Take a straight edge and check the deck for a flat surface, use feeler gauges to measure any gaps between straight edge and deck.
Do the same for the head.
Let us know what you find.
BrownStainRacing
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Grap you some flat washers and that gasket sealer @Denny recommended, on you way home.
It's very rare to have a warped head or deck on these, unless it got super hot. I run my junk 300+ degrees, haven't warped any.
Ok i will try that tomorrow thankyou
Denny
Canned Monster
You did torque the head properly? Right?
Yes
I put the shims and head gasket sealant it want turn over with the electric start tho so i think there may to to much compression
BaconBitRacing
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Check valve lash before you pull it apart, you can find specs online.
They were right
BrownStainRacing
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How about the pull start. How does it feel???
Any mods or upgrades ??
Flywheel, ignition timing will cause hard to pull start.
Its got a different carb new 45lb valve springs timing key exhaust and intake
But i didnt used to have this problem its a recent thing and i have had those mods for almost a year
BrownStainRacing
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Some thing definitely changed.
Did you verify the ignition timing with a degree wheel, or jus add a key??? It should have not changed, but these can be so unpredictable.
Dropping the timing down will help with hard to pull.
I would put the stock key back in, or turn the advanced key around and try that, see if it blows the gasket again. That lil bit of timing is not gonna kill power that bad.
BrownStainRacing
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The small blocks will run too, with a leaky head gasket, power will be way down, air/ fuel mix will be all jacked up.
And you checked with straight edge???