Adjustable push rod query

mgbv8 · Post by **mgbv8** » Sun Sep 30, 2007 6:51 pm

I have fitted adjustable rods to the new 4.6 and have set the pre load to 50 thou. If I want to do any adjustments, how can I reset the preload?
Do I back them off and then open them up until I feel the slack take up, then adjust using a digital vernier to measure between two reference points on the push rod?

kiwicar · Post by **kiwicar** » Sun Sep 30, 2007 7:34 pm

Hi
afraid it is a case of take out the lifters, drain them of oil, put them back together again and reset the preload as you did when you originally set them up (ie push em down and measure the gap to the retaining ring). Hydraulic lifters are designed to be, and are very good, at coping with variation in manufacturing tollerence and component wear but not designed for precise set-up.
in fact if you are just going to move the rocker shaft up or down a bit on shims I would just lengthen or shorten the pushrods by about the same amount (if you know what pitch the thread is on the push rods just work out how far to turn the end) and the lifters will just take up the rest.
have fun
Mike

mgbv8 · Post by **mgbv8** » Mon Oct 01, 2007 8:06 am

I guessed you were going to say that Mike. I was hoping it would be a case of adjust until you feel a bit of resistance then measure the adjustment at the top of the rod somewhere. Hmm, the lifter draining is one of my fave jobs. I'm happy I got it right on thr build, but the other probs I'm having at the mo have made me suspect everything.
Ill leave the top end alone until I have sorted my timing etc.

kiwicar · Post by **kiwicar** » Mon Oct 01, 2007 11:01 am

you'll just have to go solid roller cam now!

Mike

mgbv8 · Post by **mgbv8** » Mon Oct 01, 2007 4:59 pm

I've not done much research on a solid cam. Why do they call it a solid cam? Does the cam have rollers? Do I use solid lifters and pushrods with adjustable tappets?
I better get reading eh?

kiwicar · Post by **kiwicar** » Mon Oct 01, 2007 8:41 pm

Hi try the compcams website, and the hotrod website, both have alot of info at many levels.
basics are,
"hydraulic lifters" have a resivoir that acts as an automatic adjuster that takes up the slack in the valve train.
"solid lifters" are just that solid, no self adguster you need adjustable push rods or better adjustable rockers.
flat tappets have a flat face that rides on the lobe of the cam
roller tappets have a roller/wheel that meets the lobe of the cam.
so you have 4 basic types of lifter/tappet, each needs a different cam profile and treatment to the face of the lobe.
hydraulic lifters are low maintanence, fit and forget but limit top end revs.
solid lifters are generally lighter and allow more revs.
roller lifters allow a much more agressive opening of the valve by the cam (this tends to give a wider power band for a given timing).
have fun
Mike

mgbv8 · Post by **mgbv8** » Tue Oct 02, 2007 3:13 pm

Thanks Mike
Info duly noted. I'm off to do some reading.
Perry