screemn

found a pair of gt40 iron heads , did a lot of home porting and opening then up then when done had local engine shop do a complete valve job and make sure all was well with them....now the issue ...when ive gotten back together I used all factory parts rockers and such but did install new lifters as I did upgrade cam as well...so, all are stock parts , I am getting about a third of a turn of preload on all 16 rockers when I get my 20lbs torque spec...the car starts and runs great , but have not been able to get the valve train to be as quite as it should be...do I need more preload? and if so how do I go about getting it considering nothing is adjustable in the valve train ....thanks to any with info

proeagles

Sounds like your push rods are a tad too long. Even though the parts are stock they may not be matched plus any machining of the deck and heads could have reduced the height of the deck making your push rods too long as well. Just a thought.

screemn

Do you mean the push rods are a little short?...right? If they were longer id be able to get more preload...

mongolchuck

There isn't adjustment in a hydraulic valve train. The lifters will take up the slack. Did you soak the new lifters in oil before putting them in? It might take a while to pump them up with oil. Also a lot of what sounds like valve noise is exhaust leaks at the manifolds/headers.

88 orangepeel notch

+1 ^^^

proeagles

This is true to some extent, if the push rods are too long there won't be any hydraulic play in the lifter and if the push rods are too short, the lifter won't push the valve all the way open. That is why when you "adjust" hydraulic lifters you set the lash with 1/2 turn after the push rod stops turning as you crank the rocker down on it.

screemn

thanks for the input all...but like i said i am getting 1/3 of a turn of preload at the 20 lbs of tourqe...seems like people like a full turn or at least 3/4 turn ...maybe a 1/3 of a turn isnt quite enough?...heck i dont know ...has anyone ever used adjustable pushrods before ?....had any luck with them ? thanks for any info....i did not soak the lifters but primmed the heck outa the system everything is surely stuffed with oil

proeagles

Honestly, I've never heard of torquing the preload of a lifter. If all the parts match up, you simply put the valve in the closed position, crank the push rod down till it doesn't twist with your fingers, and then crank it 1/2 to 1 full turn, tighten the jam nut and move on. Try it.

bluebeastsrt

It seams over simplified. But that's how I've done it in the past also.

mjr46

Guys.............you all are missing one key element, which most do it yourselfers often do as they don't have the full grasp of what changing things can affect, such as different cams installed with different base circles than oem , valve jobs, ect ect...... since the cam has been changed, base circle is most likely a tad different than oem which can change lifter height, inturn this can affect push rod length "needed" and the fact that a valve job was done this will sink the valve further in the head thus often requiring valve tips to be ground to maintain stem height for proper geometry, also hopefully the machine shop set spring installed height up....so in short the issue you have most likely is a result of the valve job and cam base circle, what you need to do is measure now for push rod length and are you using stock pedestal rockers??