So using the comp pushrod length checker, I came up with 9.75 turns to zero lash with the #1 cylinder at TDC on the firing stroke (cam on base circle). By my math:

9.75 x .050 = .4875 + 6.8 = 7.2875 before lifter preload.

7.2875 + .080 for LS7 lifter preload = 7.3675 total pushrod length.

So my questions are, am I using the correct preload for the LS7 lifters, what length should I order, and any recommendations on brand?

Thanks for the help

 

Your math is right, I'm guessing it's a fairly moderate aftermarket lobe but it will help people verify your zero-lash measurement if you post the cam specs and manufacturer.

For example, my TR224 cam measured 9.25 turns to zero lash and had 0.563" gross valve lift.

You'll be rounding to the nearest 25-thousandth of an inch (assuming Trend off-the-shelf pushrods) when buying pushrods unless you go with custom ones.

7.350" rods yield 0.0625" preload according to your measurement;
7.375" rods yield 0.0875" preload " ".

 

PS: did you measure both intake and exhaust? Same measurement for both?

 

yes both intake and exhaust were the same measurements....9.75 turns. Cam is a 230/232 592/595 on a 111 LSA

 

other opinions on brand of pushrod?

 

Trend makes them for Comp and other vendors and just puts their name on them. Buying direct from Trend is fast and less expensive. Trend made my 3/8 double taper pushrods, they were beautifully machined.

Have you considered a larger OD pushrod such as the Manton 11/32"?

 

I am so confused on pushrod length checking. I am waiting to fire the motor and let the lifters pump up before checking them again. Hopefully I wont do any damage to anything while the motor is at idle.

Chad

 

I've never measured this way. If you measure the base circle of the cam, subtract that from factory base circle, subtract how many .001" your heads are milled, then subtract that number from 7.400 (factory length push rod), you will be able to get very, very close to the length you need.

That PR length seems pretty damn high for that size cam. I wouldn't imaging base circle being any different than factory on a cam that small.

 

yeah the whole pushrod length thing is confusing to me