I have used the information ive found to calculate my lifter preload but to be sure ima use a pushrod length checker after I get it all together. Here is what I have calculated it as being.

7.380 Stock Pushrod
0.025 LS6 Cam Base Circle Diff
-0.060 LS7 Lifter cup is .060 shallower (FIXED)

7.345 My Pushrod Size
0.080 Plus Preload

7.425 Total Pushrod Length


Isnt adding the preload to the pushrod size correct?

 

I don't believe you would add the preload amount. Usually, as far as correct geometry would go, you'd use a pr checker and a solid lifter and check the geometry, going with the adjusted length as the correct pr.

I may be wrong.

 

well then if i had the 7.350 pushrod, the lifter would have no preload and would be really noisey and loose if im correct

 

You want to add 1/2 of the lifters total travel that way you're operating it in the middle of it's working range.
If the lifters total travel is .160'' then .080'' is right.

 

well gm recommends .080 - .100 preload

 

If the base circle of the ls6 cam is .025 larger than the ls1 cam then your calculations look about right .

 

After you measure with the checker, add .080 to .100 and that's your pushrod length.