Hi read thrugh a very very logn article about mid lift theory and it explained very well what is actually caused when the wrong pushrod size is chosen.

Well I know now how to measure, but what I still don't understand is how to measure correctly when I have hydraulic lifters. I understand I just use a solid rocker and adjust the rocker to zero play. but how would I know the mockup lifter has the correct size? do manufactures have a mockup lifter for all different lifters they sell?

how does it work?

Kalli

 

You ought to be able to measure both the solid and hydraulic lifters for overall length and depth to their pushrod seats with vernier calipers and determine any basic length (height?) difference for yourself. What I'm not sure about is how the hydraulic lifter preload movement would figure into it all.


Norm

 

that's exacltly what I'm having trouble with. if i'm supposed to measure correctly to 0.05" or better, then i need a mockup lifter that is the exact same size as a hydraulic one while running ?!

 

uuuuuugggghhhhh. I just went through this with my GT40 heads and getting the right pushrods. I am assuming you have bolt down rockers so getting the right preload is critical. I don't have my book with me, but it depends on how many turns it takes from zero lash to the correct torque spec.

I can do it now better than I can explain.

 

no they're stud mounted, not pedestal. adjustable.
if they were solid lifters, it would be easy. zero lash+half turn, then check. but the hyd lifters confuse me

 

Hydraulic's need preload. It's usually zero lash and then a half turn or 3/4's depending on who you talk to.
If you are worried about the geometry you need to paint the valve stem tip and make sure the roller tip rides right on the stem.

I have never done solid lifters, but I believe they would need a feeler gauge to adjust the lash.

Here's a good page for both
http://www.centuryperformance.com/ad...h-spg-149.html

 

I'd call comp cams and ask their techies. They've been helpful for me in the past, even if i've had to wait on hold forever.

 

Tad: will do just that. thx!
scootchu: thx for the article, that helped clarifying the preload

 

Use the lifters that you will actually be using in the engine for the test. The way you can do this is to use a "checking spring" in the place of your regular valve spring. The checking spring is a very light pressure spring. This will allow you to use the push rod length checker without collapsing the lifter.

 

great idea, but as I understood you have to preload a lifter so that the lifter actually works. (~0.03"). so i probably have to add that later to the pushrod lenght?! anyway. I'll keep researching if there's a way without me having to change valve springs. i want to do at least 2 cylinders intake and exhaust side. so that means I need more tools ...
If i find a different method, I'll post it !!