LQ9 piston/valve clearance/compression
LQ9 piston/valve clearance/compression I had had an oil pressure problem so I pulled the motor and bought a stock LQ9 from an escalade and dropped that in and bolted on my P&P 5.3L heads with 2.02/1.5 valves and tr236 cam (has around .600" lift) that I used on the LS1. I didn't check clearance or anything.
I got it all together and the engine ran fine (noticed some noise which sounded like the annoying LSx valvetrain noise), adn eventually got quieter - I assume lifters pumped up. I drove it for around 10k miles or so then after some high rpm runs on the hwy, it started running really bad/missing/vibration, I thought it was a lower end issue, broken rod, spun bearing, etc.
I just took the heads off yesterday and found piston-valve contact and and bent valves.
Now my question is, why would I have no clearance issues with the LS1, but have clearance issues with the LQ9 with the same setup? Does the stock LQ9 have a greater piston height and less clearance than the4 LS1s? I was under the impression that if I had an LS1 with x heads and x cam, that I would just swap them over and have the same CR and clearance.
When I spin the engine over I did notice that the pistons do go protrude up above the deck slightly at TDC, I didn't notice that with LS1 so maybe like for like, the LQ9s do have less clearance and higher compression due to higher piston height in the bore?
I got it all together and the engine ran fine (noticed some noise which sounded like the annoying LSx valvetrain noise), adn eventually got quieter - I assume lifters pumped up. I drove it for around 10k miles or so then after some high rpm runs on the hwy, it started running really bad/missing/vibration, I thought it was a lower end issue, broken rod, spun bearing, etc.
I just took the heads off yesterday and found piston-valve contact and and bent valves.
Now my question is, why would I have no clearance issues with the LS1, but have clearance issues with the LQ9 with the same setup? Does the stock LQ9 have a greater piston height and less clearance than the4 LS1s? I was under the impression that if I had an LS1 with x heads and x cam, that I would just swap them over and have the same CR and clearance.
When I spin the engine over I did notice that the pistons do go protrude up above the deck slightly at TDC, I didn't notice that with LS1 so maybe like for like, the LQ9s do have less clearance and higher compression due to higher piston height in the bore?
probly just the combination of parts, the lq9 has flat top pistons and with your non stock valves you were probly close on ptv clearance,, but i think you probly have weak/bad valve springs and probly had some valve float at high rpm and bent the valves
you would not get 10,000 miles out of an engine with ptv clearance issuse
this is not possible,, your going from a 5.7L to a 6.0L engine but you are keeping the same cc heads,, your compression has to go up, you cant assume anything like this, it always needs to be checked when you mix and match parts
you would not get 10,000 miles out of an engine with ptv clearance issuse
this is not possible,, your going from a 5.7L to a 6.0L engine but you are keeping the same cc heads,, your compression has to go up, you cant assume anything like this, it always needs to be checked when you mix and match parts
probly just the combination of parts, the lq9 has flat top pistons and with your non stock valves you were probly close on ptv clearance,, but i think you probly have weak/bad valve springs and probly had some valve float at high rpm and bent the valves
you would not get 10,000 miles out of an engine with ptv clearance issuse
this is not possible,, your going from a 5.7L to a 6.0L engine but you are keeping the same cc heads,, your compression has to go up, you cant assume anything like this, it always needs to be checked when you mix and match parts
you would not get 10,000 miles out of an engine with ptv clearance issuse
this is not possible,, your going from a 5.7L to a 6.0L engine but you are keeping the same cc heads,, your compression has to go up, you cant assume anything like this, it always needs to be checked when you mix and match parts
I definitely didn't check the clearance, just carried it over to the LQ9 shortblock, apparently it was a bad assumption - lesson learned. Thanks for the input.
