Inconsistent Pushrod Measurements
03-07-2013, 03:07 PM
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Inconsistent Pushrod Measurements Just torqued the heads down after a cam swap and am measuring for new PR length.. On one head I got perfectly consistent measurements but the other has varying results. The heads are unported ls3 heads. I know the intake valves are just a smidge longer but i'm having trouble thinking of anything that would cause such a wide range of results
03-07-2013, 07:06 PM
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Okay, I just went back and double checked the measurements. One of the intakes measures zero lash at 9.5 turns.. I take it out and stick it on the intake valve of the cylinder right next to it (making sure of course the lifter is on the base circle) and there's lash until 10 turns I can't think of a reason why only one head is giving me such varied measurements when the other side is just fine. Could I have a problem with the lifters? I did make sure that all of the lifters were pushed down on the cam before attempting all measurements. I even took the rocker stand out and looked it over to make sure it wasn't bent.
03-07-2013, 07:32 PM
#5
Man I've been playing this same game today. If I run my comp pushrod checker up to about 7.3" overall I get preload anywhere from .030 all the way up to .090. What I've been doing is running the pushrod checker up to zero lash and then counting the turns on the rocker bolt to get 22lbs torque. The idea is that each full turn is ~.047. So between 1.5 & 1.75 turns from zero lash is .070 to .082 of preload. Mine are all over place so at this point I'm probably going to pick a pushrod length somewhere in the middle. Some will be right, some will be more & some will be less.
03-07-2013, 07:41 PM
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Weird, I was just in the garage doing the EO/IC method. I cam up with 1.25 turns on all of the ones I tried.. I stopped and turned to one of the valves I have been getting funny measurements on. The EO/IC method took about 2.5 turns to get to 22 ft/lbs and zero lash with the checker is 9.5 turns which is way off from the rest. I can take the pushrod and pretty easily press the lifter down. Much more easily than the others...
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03-08-2013, 10:02 AM
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Well I just tried your method. I did all the valves on cylinders 1,2,3 & 4. My engine is in the car and it's more effort than I'm willing to put forth to get to the back four. To get zero lash on my checker took anywhere from 8.5 to 9 turns. It looks to me like a 7.3" pushrod will get me anywhere from .050" to 0.075" of preload. A 7.325" pushrod will get me in the range of .75" to .100" of preload. All in all, I'm good with that, the question is do i want more or less?
03-09-2013, 12:18 AM
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Well I just tried your method. I did all the valves on cylinders 1,2,3 & 4. My engine is in the car and it's more effort than I'm willing to put forth to get to the back four. To get zero lash on my checker took anywhere from 8.5 to 9 turns. It looks to me like a 7.3" pushrod will get me anywhere from .050" to 0.075" of preload. A 7.325" pushrod will get me in the range of .75" to .100" of preload. All in all, I'm good with that, the question is do i want more or less?
03-09-2013, 02:49 PM
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I cam up with 1.25 turns on all of the ones I tried.. I stopped and turned to one of the valves I have been getting funny measurements on. The EO/IC method took about 2.5 turns to get to 22 ft/lbs and zero lash with the checker is 9.5 turns which is way off from the rest. I can take the pushrod and pretty easily press the lifter down. Much more easily than the others...
03-13-2013, 01:43 AM
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Well, originally I was using the comp pushrod checker but have since been experimenting with the rocker bolt method. On cylinders 2-8 I got about .75 to 1 full rotation till 22 ft lbs. and on the other bank I got about 1.25 to 1.75 turns till 22 ft lbs. Is this difference something I should be worried about? I did the measuring with 7.4 stock push rods