1madss

iTrader: (10)

While I hate to bump such a contentious thread I am going to post what I have found in MY setup.

LS2 402, PRC237 heads, FTI cam and stock rockers w/ Comp upgrade.

I am in the process of repairing a good deal of damaged parts after a ls7 lifter failure a couple of months ago that took out a lobe on a rather expensive cam as well as a number of other parts. In the process of refreshing my memory on preload I came across this thread and being that I am in the process of putting the top end back together I went ahead and actually measured my preload with a dial indicator this time instead of just counting turns. I always struggle a bit with finding zero lash as it seems to be a bit subjective.

In measuring a number of times across a number of valves both tightening and loosening I came up with the same results ~.075 per full turn of the bolt. This is measured with a dial indicator on the tip of the end of the rocker arm directly over and in line with the pushrod.

Don't know what to say. All I know is what I actually measured in my setup.

Not trying to discredit or lay blame on anybody but myself for the damage. I should have broken out the dial indicator first time around and saved myself a lot of work and $1000 in parts.

SPRAYED 01

iTrader: (22)

Thanks. So what did you have it set to that caused the damage?

1madss

iTrader: (10)

7.50" pushrods put me right at ~.130"



Had to replace lifters as well as cam,oil pump, timing chain tensioner (damned LS3 tensioner ) timing chain and a valve spring and seal.

pinhead

I have brought this tread back from the dead because I have been pulling my hair out measuring for pushrods this weekend and the 0.047 is wrong
I have been using a pushrod checker and getting massively diferent results to the turn bolt method but if you use 0.049 x 1.7 then I am within a couple of thou of the checker I double checked my work by using pushrod checker to find zero lash then open up 1 full turn 0.050 and then turn the bolt method gets a little over half a turn to snug down it should go a full turn if 0.047 was correct

Now I have brought this thread back because people need to know about the mis information out there and I have to wonder when you read threads about cams getting wiped out and blaming manufacturer for poor quality if it is actually people running too much pre load

Andy

soundengineer

iTrader: (16)

1 turn = .078
its been said 9 million times on this forum.
myself and several others have even given hard proof with videos and pictures.

pinhead

Could some of the true posts be stickied as I searched rather than asking what had been asked time and time again and found very few posts like this but pages of results that state 0.047 or links to that instructional

SPRAYED 01

iTrader: (22)

WOw crazy this was bumped up.

I started this thread like 4 years ago when I was doing springs and measuing for proper push rod length. 4 years later and I am rebuilding my engine because a lifter broke, lost some oil pressure and burnt up some main bearings.

Back then I just used a dial indicator to make sure I had the correct preload so I dont think thats the reason the lifter failed. LS7 lifter with xer lobes and some trans shifting issues so bad rev limiter bouncing at 900whp, turbo car could have been a factor.

SPRAYED 01

iTrader: (22)

I will be back at it in a couple week this time with morel lifters.

One thing, does it matter when finding 0 lash if the lifter has oil in it or is brand new and no oil?

Thanks
Alex

Darth_V8r

iTrader: (4)

Yeah, and it's not even that hard to do the math to verify it. What also adds to the confusion is people continue to count the torquing of the bolt as part of the rotation. Torque means you're stretching the bolt for clamping force and by definition are no longer adding preload.

The most reliable method imo continues to be to find zero lash and then mathematically add desired preload. Use rocker bolt rotation ONLY AS A DOUBLE CHECK, not the primary metric.

There's a couple different how-to's out there, but not sure if either ever got stickied