Exhaust valves hitting pistons....help!
Thread Starter
Teching In
Joined: Jul 2016
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Exhaust valves hitting pistons....help! L33/5.3L being rebuilt. Exhaust valves hitting pistons. Flat top pistons. Texas speed cam with following specs: 220/220, .600/.600 112LSA 110ICL. Cometic head gaskets .040 thick. Stock valve. I don't know what the stock head gasket thickness is, the .040 thickness was recommended by texas speed. Heads and block were not decked. Was installing rockers and found all exhaust valves will hit pistons. So will a thicker head gasket clear the valve or do I have to run a different cam? Obviously the cam was recommended by Texas Speed. Thanks for the help, pretty discouraged right now!
I think the cam is not on a 110 centerline. The exhaust valves are smaller than the intake valves. Typically, you'll hit the intake valves first. if the exhaust valves are hitting and intake valves are not, it sounds like the cam and/or timing is off.
Only times I've ever seen exhaust valves hit pistons are:
1. Mechanically over-revved engine (money-shifting third to second at the top of third)
2. Broken timing chain
3. Timing chain off by teeth
Only times I've ever seen exhaust valves hit pistons are:
1. Mechanically over-revved engine (money-shifting third to second at the top of third)
2. Broken timing chain
3. Timing chain off by teeth
Thread Starter
Teching In
Joined: Jul 2016
Posts: 37
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I hope it isn’t in the right place! I’ll pull the cover and double check. I’m not going to claim that I’m overly knowledgeable about cams or installation: been a while since I installed. Ill follow up shortly. Thanks for the quick replies.
Thread Starter
Teching In
Joined: Jul 2016
Posts: 37
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Man I feel dumb....timing gear and crank not lined up....not sure how the heck I overlooked when assembling. Must have thought at some point I'd line it up before putting on the cover, came back and just put the cover on without fixing.
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Split Overlap Measurement Hi Rock, good news with NO bent valves reported.
This CASE is a perfect EXAMPLE of HOW EASY (SIMPLE) it is to TDC the engine #1 & #6 then MEASURE Valve Lifter distance FROM THE DECK. (1&6)
BOTH lifters in each cylinder, I&E paired, should be the same distance out of the lifter bore if any.
The Rock case, if measured, would have found the EX lifter was much higher than the IN lifter.
FINDING this error would have stated the Cam Timing was not correct !
MY findings are that there ARE Timing Sets being "miss-marked".
THUS I do not trust the dot/dot alignment.
Lance
This CASE is a perfect EXAMPLE of HOW EASY (SIMPLE) it is to TDC the engine #1 & #6 then MEASURE Valve Lifter distance FROM THE DECK. (1&6)
BOTH lifters in each cylinder, I&E paired, should be the same distance out of the lifter bore if any.
The Rock case, if measured, would have found the EX lifter was much higher than the IN lifter.
FINDING this error would have stated the Cam Timing was not correct !
MY findings are that there ARE Timing Sets being "miss-marked".
THUS I do not trust the dot/dot alignment.
Lance
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