lifter preload experts take a look** video added
08-25-2012, 11:36 PM
#1
lifter preload experts take a look** video added hey guys i recently redid my 4.8 turbo set up with some better valve springs and while i was at it upgraded the ls6 style lifters i had in it to the ls7 style. with the ls6 lifter i used a 7.375 push rod and got just at or under 1 3/4 turns till 22 ft ibs. with the new ls7 lifters im getting a tad over 1 3/4 turns and when i fired it up it clanked and rattled like all heck. it finally started to idle quietly as i left oil pressure flow threw the lifters but as soon as i would try and rev it it would get noisy again and clank around and stall. i think the push rods are to long , after reading around i think i want to order a push rod thats 30 thou shorter. the chart i saw said that 30 thou would equal about a 3/4 of a turn and im a tad over 1 3/4 now. does this all sound correct? so if i have a 7.375 now i want a 7.345 correct? also does any one think i hurt any thing running it? it does run quiet as long as i let it idle if i rev it thats only when it starts to clank around.
here is how it sounds, idles and drives fine with no sound until you rev it up and then it clanks for a while. have to sometimes shut it off and wait a little then restart for the clanking to stop, i thought maybe the lifters bleed down some during that time or some thing. most the time it clanks even worse then this.
http://www.youtube.com/watch?v=X-oLN...ature=youtu.be
here is how it sounds, idles and drives fine with no sound until you rev it up and then it clanks for a while. have to sometimes shut it off and wait a little then restart for the clanking to stop, i thought maybe the lifters bleed down some during that time or some thing. most the time it clanks even worse then this.
http://www.youtube.com/watch?v=X-oLN...ature=youtu.be
Last edited by lavoy; 08-26-2012 at 12:33 PM.
08-26-2012, 12:43 AM
#2
You should always prime hydraulic rollers by turning the motor over without firing in order to release air pockets in the internal pistons and allow the oil pump to prime them to proper spec - another common way is soaking them in oil for 24 hours with the venting holes straight up prior to installation. Either way air pockets need to be vented.
Next is proper installation. You will need this if you do not already have one: http://www.summitracing.com/parts/CCA-7702-1/
Remove the rocker and install this pushrod. It is recommended that you use check springs but not essential - i have seen it done with and without. Bottom the lifter out on the valve that you are checking. Torque the rocker to 22ft lbs. Adjust the pushrod for zero lash. Remove the rocker and measure the pushrod. Add 0.066-0.084 for proper LS7 lifter pre-load and this is the final installed pushrod length that you will need.
There is one thing i did not touch basis on, and that is proper valvetrain geometry with emphasis to proper travel of the tip of the rocker in relation to "over the nose" of the valve. It should travel as ideally as possible over the center of the valve throughout the valve event. If the rocker arms are adjustable and have lockout nuts, you can adjust both the rocker arm and the pushrod length to get the proper geometry over the nose of the valve. Once this is done lockout the rocker and begin normal procedure for zeroing lash.
If you do not have lockout nuts for adjustable RR's (with aftermarket RR's) then you cannot adjust valve stem wipe over the nose.
Next is proper installation. You will need this if you do not already have one: http://www.summitracing.com/parts/CCA-7702-1/
Remove the rocker and install this pushrod. It is recommended that you use check springs but not essential - i have seen it done with and without. Bottom the lifter out on the valve that you are checking. Torque the rocker to 22ft lbs. Adjust the pushrod for zero lash. Remove the rocker and measure the pushrod. Add 0.066-0.084 for proper LS7 lifter pre-load and this is the final installed pushrod length that you will need.
There is one thing i did not touch basis on, and that is proper valvetrain geometry with emphasis to proper travel of the tip of the rocker in relation to "over the nose" of the valve. It should travel as ideally as possible over the center of the valve throughout the valve event. If the rocker arms are adjustable and have lockout nuts, you can adjust both the rocker arm and the pushrod length to get the proper geometry over the nose of the valve. Once this is done lockout the rocker and begin normal procedure for zeroing lash.
If you do not have lockout nuts for adjustable RR's (with aftermarket RR's) then you cannot adjust valve stem wipe over the nose.
Last edited by SS10Tech; 08-26-2012 at 12:49 AM.
08-26-2012, 10:40 AM
#4
neither of these post are relevant to what i asked, i dont need a tool i have a home made one. but you can also go off the turns on the bolt because the thread pitch is known and consistent . on the last ls6 lifters the number of turns was on the high side and it didnt sound like this so i figure maybe the ls6 lifters could handle more preload or something.
08-26-2012, 11:13 AM
#5
hey guys i recently redid my 4.8 turbo set up with some better valve springs and while i was at it upgraded the ls6 style lifters i had in it to the ls7 style. with the ls6 lifter i used a 7.375 push rod and got just at or under 1 3/4 turns till 22 ft ibs. with the new ls7 lifters im getting a tad over 1 3/4 turns and when i fired it up it clanked and rattled like all heck. it finally started to idle quietly as i left oil pressure flow threw the lifters but as soon as i would try and rev it it would get noisy again and clank around and stall. i think the push rods are to long , after reading around i think i want to order a push rod thats 30 thou shorter. the chart i saw said that 30 thou would equal about a 3/4 of a turn and im a tad over 1 3/4 now. does this all sound correct? so if i have a 7.375 now i want a 7.345 correct? also does any one think i hurt any thing running it? it does run quiet as long as i let it idle if i rev it thats only when it starts to clank around.
The problem I see however, is that the motor should run with either of those preloads (the "tad over" 0.111 or 0.0782). So you may have some issue other than just preload.
08-26-2012, 12:05 PM
#7
At 1 3/4 turns I calculate the preload to be at 0.111 inches. At a "tad over" is somewhat more. If you go go 0.030 inch shorter pushrod your prelaod will be a "tad over" 0.0782 inch.
The problem I see however, is that the motor should run with either of those preloads (the "tad over" 0.111 or 0.0782). So you may have some issue other than just preload.
The problem I see however, is that the motor should run with either of those preloads (the "tad over" 0.111 or 0.0782). So you may have some issue other than just preload.
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08-29-2012, 03:42 PM
#13
Could be the lifters bleed down from the push rods being too long. At higher RPM, the lifter might bleed down just enough for the lifter's plunger to bottom out inside the lifter body. After the engine idles for awhile, the lifters pump back up just enough to keep the plunger off the bottom of the lifter body.
As others have suggested, you need to get shorter push rods in there to see if that's the cure.
I didn't see any mention of your oil pressure at higher PRM ... is it good?
As others have suggested, you need to get shorter push rods in there to see if that's the cure.
I didn't see any mention of your oil pressure at higher PRM ... is it good?
08-29-2012, 08:28 PM
#14
listening to the video it sure sounds like too much preload to me. what you posted backs up again the fact using number of turns on the rocker is a flawed method.... with the ls7 lifter you should have subtracted .050 from the push rod length. you showed almost the same preload using the rocker method.
my advise is to use the comp cam tool and verify.
my advise is to use the comp cam tool and verify.
09-18-2012, 03:59 PM
#16
problem ended up being small pieces of shrapnel from the previous blown motor had puked into the intake and even though we thought we got it all out we missed some and it sucked in and was banging around between the piston and head. all fixed and sorted now, but i did go to a shorter push rod any way, now im 1.25 turns.
