high rpm miss
high rpm miss iv been throwing parts at this thing for a while now and i cant seem to get it right. it misses at WOT above 5500. new GM opti, MSD coil, Airtex fuel pump, ACdelco fuel filter, red top injectors, ACdelco regulator, GM icm, NGK TR-6s (had TR-55s, did it then too), it has a bad tune on it but i dont see how that could be it. iv been told my roller rockers need to be re-adjusted. it has LS7 lifters
It could be the tune, if its bad enough... Never know whats going on with that...
What have you checked in the order of cheap stuff (coil/icm - fuel pressure - plug wires, anything)? Even though its all new, something could be defective and giving you trouble. You mentioned someone said that your roller rockers needed to be adjusted, who told you that, do they know anything about cars? Do the rockers make excessive noise?
Since you have an AI cam, I assume you called them and they set you up with the proper springs? Your problem sounds almost like valve float but if AI set you up with springs it couldent be.
What have you checked in the order of cheap stuff (coil/icm - fuel pressure - plug wires, anything)? Even though its all new, something could be defective and giving you trouble. You mentioned someone said that your roller rockers needed to be adjusted, who told you that, do they know anything about cars? Do the rockers make excessive noise?
Since you have an AI cam, I assume you called them and they set you up with the proper springs? Your problem sounds almost like valve float but if AI set you up with springs it couldent be.
the guy that told me that is an ase certified mechanic that scored perfect on his last ase test. i did adjust the rockers before the new lifters had broken in. you can hear them when idling but im told roller rockers make that noise
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well, after setting each cylinder to TDC, i turned the nut until the pushrod had some resistance to turning, then tightened it a 1/4 turn, tightened the lock, then turned the whole thing about an 1/8-1/4 of a turn.
"spin the pushrod" almost always results in too tight, often WAY too tight.
When the polylock touches that is zero, not even finger tight on the polylock, just touching and then try and move the pushrod inline between the rocker and lifter.
This is a VERY VERY common problem. I have no idea why this bad way of adjusting is so popular, it causes a lot of guys a lot of problems.
When the polylock touches that is zero, not even finger tight on the polylock, just touching and then try and move the pushrod inline between the rocker and lifter.
This is a VERY VERY common problem. I have no idea why this bad way of adjusting is so popular, it causes a lot of guys a lot of problems.
Teching In
Joined: Aug 2008
Posts: 17
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i tried that spin the pushrod thing and it didnt work for me.. i had to start the car and with it running, i wold tighten each poly lock by hand until it quit chattering then tighten the allen head afterwords, backing off a half a turn, then tightening the allen head and going another half turn to get back to where it quit making the ticking sound ... seemed to work for me
And FTR, I have NEVER had a problem doing them this way. Mine are currently set at 1/8 past zero lash + a little bump of the polylock.
Engine has been running for 3-4 months now and haven't had to re-adjust anything. well i went out and readjusted my rockers. this time with the car running i loosened and tightened on cylinder at a time. with it running i tightened it until it stopped tapping, shut the car off and tightened it 1/2 a turn total. i did all 8 cylinders and took it for a ride. nothing changed. i did notice that after a couple hundred rpms it does seem to go away. but i dont want to push it much higher than that. i wouldnt think a tune would cause this but then again i dont know anything about tuning. ill call HPE tomorrow and ask them. this may sound stupid but is it possible to over power the stock rev limiter?
sounds like a valve problem to me....and on a stock bottom end you shouldnt be running it much past 5500 anyways...it will take out your bottom end...was this running for the dyno or something
I have never bothered with running adjustment. Did you have asecond person turning the car off or did you have to let go of the wrench to turn it off?
Tuning issues can cause a whole lot of troubles.
Stock bottomend is fine beyond 5500, most of us find 6500rpm to be a more realistic limit.
If you have datamaster shoot me a PM and I will give you my email addy so I can look at a log.
Tuning issues can cause a whole lot of troubles.
Stock bottomend is fine beyond 5500, most of us find 6500rpm to be a more realistic limit.
If you have datamaster shoot me a PM and I will give you my email addy so I can look at a log.
no i dont have a datamaster but i think i found my problem. i hooked up a fuel pressure tester and took it for a spin. it held a constant 40 psi until about the time it starts missing. at one point it dropped to 30 psi. so i guess im gonna go ahead and get a granetalli fuel pump.