Ford Mustang Forums banner

1 - 4 of 4 Posts

·
Registered
Joined
·
155 Posts
Discussion Starter #1
Ok i know this is over done, but it still seems to never work out right. Ok i know how to get the valve and cam in the right position. But the problem is "zero lash" and tightening. Ok i've heard zero lash is when you start catchin some drag on the pushrod, and then tighten a 1/2-1 turn after that or 18ftlbs. Well i can always rotate my pushrods, in the neutral position, and when you turn the engine over everythingt changes on that cylinders valves, you can tighten it more. So do i just so so i just tighten it up on the first alingment ? When you tighten the rocker down is the valve spring supposed to start to compress ? What i mainly need to know is where zero lash is. I have th FMS 1.6 blues pedestal mount roller rockers. I've tried it a lot and have never felt a 100% about it. So please explain your zero lash please, and how tight the bolt should be when you start to tighten it. I'm doing it again after getting some loud rasp out of something at 4,000 and on in third and forth mostly. Maybe a header leak? I just used ultra high temp Permatex, The bolt were loose and i tightened them but still getting the noise. It developed after a night of driving it pretty hard for the first time since my head porting. Thanks everyone Rock ON!

Thanks for the help.
 

·
Registered
Joined
·
1,824 Posts
Zero lash is where it starts to drag on the pushrods..
thats not the best way to do it, you should go end to end and onces theres no slop left thats Zero lash..

after you get there, you want it to turn about 1/4-1 turn before it tightens up to spec, It should never get tighter....

If it turns more than 1 turn you need to shim your Rockers up..
If its less than 1/4 turn you need longer pushrods....

Each Cylinder needs to be at TDC for this to work right...
 

·
Registered
Joined
·
155 Posts
Discussion Starter #3
ttt

ttt
 

·
Registered
Joined
·
35,078 Posts
For the pair you're installing, be certain the lifters are on the base circle of the cam - that is, the valves are completely closed. TDC happens twice for each cam rotation - TDC at the end of the compression stroke is one place both valves are closed. TDC at the end of the exhaust stroke both valves are open - so not just any TDC will do. The way I do it is to rotate the engine through the exhaust valve's opening and closing; as the exhaust valve closes, the intake valve begins opening. Keep rotating until the intake valve fully closes, and then you're on the base circle of the cam. After you've adjusted that pair, move to the next pair in the firing order, and you'll only have to rotate the engine a bit to get through the next pair's intake valve closing - and you'll be on the base circle for the next pair. If you're confused or uncertain about what I'm describing, I'd suggest getting a buddy to help you the first time - someone who's really clear on this part of the procedure, someone that's done it successfully before. By the way, the engine rotates clockwise - if you're turning it the other way, the procedure I've described won't work.

Zero lash is attained simply by tightening the pedestal bolt until there is no longer any clearance between the roller tip and the valve, and no clearance between the push rod tip and the other end of the rocker. On mine, for most rockers you can reach zero lash just tightening the bolt with your fingers. I tighten the bolt with one hand, and rock the rocker with the other. When there's no more "gap" at either end of the rocker you're at zero lash. Be certain that you're not depressing the plunger in the lifter any. At that point put your torque wrench on the rocker bolt. Tighten and count the number of turns. I usually do it 1/4 turn at a time. You should hit 18-20 ft-lbs of torque somewhere between 1/4 turn and 1 turn. If it takes more than one turn to hit that torque, then you need to place a shim between the rocker and the fulcrum guide. They come in .030", .060" and .090". More than likely, if nothing has been machined on the engine (heads cut or block decked) you'll only need a few .030" shims on a few of the rockers - at least that's how mine was. If you're hitting the recommended torque in less than a 1/4 turn, then you need different length pushrods - but this probably won't happen. Take your time and work your way around all sixteen working in pairs. It'll take a bit of time done correctly, especially if you're working by yourself with the engine in the car. Hope this helps - good luck with it.
 
1 - 4 of 4 Posts
Top