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Help With Valve Clearence

cuong nguyen

By cuong nguyen,
in Engines & Forced Induction

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cuong nguyen Proficient

cuong nguyen

Posted
Posted

hey guys i had a overheating issue with my 33 gtst. it caused my head to crack. i originally thought it was my head gasket. the car was built by previous owner. so i dont know all about it. ive by told by a few ppl on here that im running a forged piston, i was also told it was 40 thou over sized too. ive added a pic of my piston so u can check it out. i pulled my head off and found out i was running a mls gasket. so i didnt blow that as i assumed first. ive chosen to go back to the standard hg but realised that my pistons stuck out a tiny bit when the motor was at TDC. i looked at my mls gasket and realised that it was like 4 or 5 layered so its pretty thick.

anyways.

my question is when i put a breaker bar on my crank bolt to see if it all rotates freely i kind of feels like that pistons are tapping the valves or hitting the head. ive got a second hand head and had it cleaned up, so its not the same head.

was my old head gasket that thick for clearance or what?

ill take photos of my old hg and measure it so u guy can see. any help would be good. originally when i bought the car the guy told me its a 2.7L stroker but i assumed he was full of it.

cheers cuong.

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89CAL Grand Master

89CAL

Posted
Posted

Measure piston height at TDC, align the cam gears with the marks on the backing plate (TDC head alignment) then you shouls be able to measure how far your valves stick out at TDC. Work out the clearance from valve to piston then buy head gasket to suit

Ben C34 Grand Master

Ben C34

Posted
Posted

Head gasket thickness is crucial on a built engine especially with a positive deck height. I wouldn't have put a thinner one on but I don't think that would actually cause the valves to hit. Have you triple checked the cam timing?

hy_rpm Proficient

hy_rpm

Posted
Posted

With any interference engine you should never turn cam and crank separately fully

That's asking for bent valves

Have cams out first allign crank to tdc then install cams to tdc and attach timing belt or you can

Have the crank just before tdc 20 so all the pistons are slightly down and then rotate the cams to tdc and then bring the crank to tdc and attach belt

If you have the crank just before tdc 20 you can rotated the cams all you like and it won't touch the pistons

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