Changing preload changes rocker geometry. There is substantial power to be had in correct geometry. The engine Crane did there testing with may have had the best geometry at 1 turn past zero lash thus making the most power. It does not necessarily mean all engines with their lifters will make the most power at 1 turn.

 

Excellent point on the rocker geometry! Therefore, the best approach for me will be to test several different preload settings and then determine which one works best for my application 1/4, 1/2 or 1 turn.

WD

 

did you ever get back to the track????

 

Yes, and I've got an opinion on Crane's tech advice about the heavy preload (1 to 1-1/2 turns).

Bottom-line, the heavy preload "does not" improve the high RPM performance with the Crane HP lifters. And, possibly the one turn of preload (.050") hurts the high PRM and something around .015 to .020 would be best.

Also, I added some new hardware to my valve-train, besides the new PAC-1518s. The performance improvement was significant!

WD

 

TPIS did a lot of dyno and track testing with lots of lifter preload and had
some very interesting results that are in line with the Crane recommendation.
I've played around a bit with 1.5 turns on a stock GM lifter and it seemed to
agree with the TPIS findings. I would say 1 turn is a very reasonable preload
without going extreme. I set my GM lifters to 1 turn now (with 7/16 studs).

 

can you guys look at my post about my 383 and see what you think

 

Because it may be a precautionary measure so they don't get smeared like Comp from those who had valvetrain troubles to start? Just a guess...

 

Awesome set up.