pre load

[steve maluk]

ok fans
i can read all day long on preload on hyd cam adjustable rockers
1/4 turn down after zero lash
1/2 turn down
up to 1 1/2 turn
340 fresh build only change single adjustable rockers
any guidance on after zero lash how far down on adjuster
thanks
sjm

 

[Dipstick]

Most adjusters have 28 threads per inch so one turn is a preload of about .036".

Some think the retaining ring style dictates the preload, and suggest adjusting lifters with Truarc-type retaining rings 1/4 to 1/2-turn down from zero lash; adjust paperclip retaining-ring lifters 1/2 to 3/4-turn down from zero lash.

 

[Budnicks]

I've always done max of like 1/2 turn, max
after I get resistance while spinning the pushrod
at 'real zero lash', while the cam/lifter is riding on the base circle
& then after tightening the allen set screw/or the lock down,
I use a wrench, like 9/16" (or 5/8" ?) box wrench on it, on the adjuster nut
against the lock/allen so it stays tight
so it's like almost 5/8's (to 3/4's) of a turn all done, max

done it on Gm, MoPar & Ford all the same, never any issues ever

 

[Geoff 2]

Most hyd FT lifters have a total of 0.150" or more internal movement. You can set the 'pre-load' [ PL ] anywhere within that range. The idea of just using a minimum of PL is that if the lifter pumps up, the power loss will be minimal because the valve is only held off it's seat a small amount. The problem is that many lifters have paper-clip type circlip that can get punched out during over revving.....with bits going everywhere inside the engine.

Much better to use more pre-load...& make sure your valve springs are strong enough to control the valve train. Lifter pump up usually occurs with the intake valves first; because they are heavier & not opening under pressure like the exh. You hear this as noise coming through the carb or throttle body....& then you back off the throttle. So you get a warning.

 

[Moms68]

Bw careful not to over tighten the lock nuts. I've had a couple stretch the threads (went too tight I guess) and break off a few days later.