sins of past owners....
10-23-2015, 01:01 PM
#43
That said, I never measured the two back to back.
10-23-2015, 01:09 PM
#44
10-23-2015, 01:11 PM
#45
There have been many reports that the LS7 lifter measures .05 inches (IIRC) longer than the LS1 lifter when installed due to increased internal spring tensions or some such mess.
This becomes important when working with a non-adjustable rocker like the stock LS rocker. From what I can tell, and I got tired of reading about it, you basically set lifter/valve preload by correctly setting pushrod length as you aren't supposed to change the torque (22lbs) on the non-adjustable rocker.
Again, you could read up on this for hours, but off the cuff, it seems .080 is the preload number that everyone is favoring and the .050 difference in length appears to be causing noisy valvetrains in some applications.
I've ordered parts and have all next week to truly figure it out but I'm on the right track...I think.
This becomes important when working with a non-adjustable rocker like the stock LS rocker. From what I can tell, and I got tired of reading about it, you basically set lifter/valve preload by correctly setting pushrod length as you aren't supposed to change the torque (22lbs) on the non-adjustable rocker.
Again, you could read up on this for hours, but off the cuff, it seems .080 is the preload number that everyone is favoring and the .050 difference in length appears to be causing noisy valvetrains in some applications.
I've ordered parts and have all next week to truly figure it out but I'm on the right track...I think.
I'd have to dig up my notes, but I think I went with 7.395
With my 102mm Fast Intake (resonating chamber), I got a tad more drivetrain noise.
10-23-2015, 04:26 PM
#46
I also get the feeling that the increased preloads lead to quicker lifter bleed downs which makes them noisy on start up.
10-25-2015, 02:37 AM
#47
buy a pushrod checker and use a digital caliper to check your findings.
Go old school and mark the top of the valve stem head with a black marker install everything and see if the marking is thin and in the middle of the valve stem head. If it is towards you its too short and if its away from you its too long. If you are using roller rocker arms.
thats the best and fastest way to find the proper pushrod length...
Go old school and mark the top of the valve stem head with a black marker install everything and see if the marking is thin and in the middle of the valve stem head. If it is towards you its too short and if its away from you its too long. If you are using roller rocker arms.
thats the best and fastest way to find the proper pushrod length...
10-25-2015, 09:26 AM
#48
buy a pushrod checker and use a digital caliper to check your findings.
Go old school and mark the top of the valve stem head with a black marker install everything and see if the marking is thin and in the middle of the valve stem head. If it is towards you its too short and if its away from you its too long. If you are using roller rocker arms.
thats the best and fastest way to find the proper pushrod length...
Go old school and mark the top of the valve stem head with a black marker install everything and see if the marking is thin and in the middle of the valve stem head. If it is towards you its too short and if its away from you its too long. If you are using roller rocker arms.
thats the best and fastest way to find the proper pushrod length...
The pushrod length gauge is indexed and machined to give you a dimension of .050" for every full turn through the indexing mark. I adjusted the gauge to the length of the stock pushrod and installed it, torqued it and noted there was no clearance between the valve tip and rocker.
I adjusted the pushrod gauge by one complete turn (thus shortening the pushrod by .050"), re-tourqued the rocker and repeated this process until I had clearance between the valve tip and the rocker.
It took 3 turns (which shortened the pushrod by .150" from stock) to give me clearance between the rocker and the valve tip (with the rocker torqued to 22lbs) and using a feeler gauge, I measured this valve clearance at .035".
3 rotations x .050" - .035" = .115" which is the preload on the lifter using the stock pushrod. To get to .080" of preload, I would need a pushrod that is .035" shorter than stock but they don't make that AFAIK.
What I haven't done is measured the length of the stock pushrod and as I don't have a set of calipers that big (and none of my immediate friends do either), its going to take a trip to the machinist because I'm too cheap to buy a set for a one time gig. Internet values for the length of a stock LS6 pushrod vary so to know for sure, I'll have to measure.
As soon as I get my VIN matched PCM, I'll let it run with the stock pushrods to see how it sounds and go from there.
10-29-2015, 12:29 PM
#49
I'm thinking I'd need to go with a 7.35 which is the next shortest pushrod I've found to stock. A set of those would put me right where I need to be but I put the stock ones back in it for now.
I also get the feeling that the increased preloads lead to quicker lifter bleed downs which makes them noisy on start up.
I also get the feeling that the increased preloads lead to quicker lifter bleed downs which makes them noisy on start up.
10-31-2015, 01:32 PM
#50
Got the PCM in and fired the car up and while its a little noisy, it isn't bad enough to warrant putting shorter pushrods in it at this point. Sounds kinda like a noisy/scrubbing belt although it has been described as the "sewing machine noise" which isn't a bad way to describe it. My other V with 237K is only slightly quieter.
If I have issues with the lifters bleeding down/noisy lifters on start up because of the dual valve springs in combination with the heavy preload I might revisit but only time will tell.
If I have issues with the lifters bleeding down/noisy lifters on start up because of the dual valve springs in combination with the heavy preload I might revisit but only time will tell.
11-18-2015, 08:31 AM
#51
After a thousand miles, I haven't seen any adverse affects of running the LS7 lifter preloaded at .115" other than the "whirring" noise that is noticeable but soon forgotten if you drive it everyday. I half way expected the lifters to bleed down over night with the added spring tension of the double valve springs in combination with the higher lifter preloads but that hasn't happened.