Chevy86 IROC-Z

iTrader: (17)

Sup guys. I just got a set of Aluminum Rocker Arms. The ratio is 1.6. Im gonna put em into my IROC as soon as possible. But before I get into the heads, How tight should I tighten these pupies down? Should I tighten till the lash or ticking is gone, then turn 3/4? . Would these fit in my IROC and will I feel any gains as in HP? I already have roller lifters in the block.

IROC343

There are many ways to do this, engine running or not. What I have found easiest is to replace them per cylinder. Turn the engine over by hand and watch the rockers, do the intake when the exhaust starts to open and the exhaust when the intake is almost closed. This makes sure you're on the base circle of the cam lobe. Spin the pushrod back and forth with your fingers while tightening the rocker down, when the push rod becomes hard to turn you're at zero lash, for performance aplications I usually go 1/4 turn more. I have found this method to be easiest with no mess. You can go more than the 1/4 turn preload if you want, I've seen specs up to 1 full turn, but this will cause a greater chance for the lifters to pump up. If you have a helper they can jog the starter to make turning the engine over easier. Just go cylinder by cylinder and make sure your on the base circle.

Chevy86 IROC-Z

iTrader: (17)

I know how to adjust the lash when the IROC is on. That's the best method IMO. But I've never done it to roller rockers. So once I get the lash out with the engine running, how much of a turn should I go?

Chevy86 IROC-Z

iTrader: (17)

On my factory crap rockers, I have 3/4 turn after 0 lash. I don't think 1/4 turn is enough.

Chevy86 IROC-Z

iTrader: (17)

what do you mean by that if I give it 1 full turn, I run the risk of a lifter "pump up."

IROC343

If you understand how a hydraulic lifter works, you'd understand why 1/4 turn is fine. If you feel better with 3/4-to 1 turn then go ahead and adjust it that way. I'd rather adjust them with the engine off, less mess.

Chevy86 IROC-Z

iTrader: (17)

if you don't mind, how does hydraulic lifters work? What do you mean by pump up?

IROC343

Inside the lifter body there is a piston. this piston rides in a bore, when the engine runs the bore is filled with oil under pressure. The piston rides on top of this cushion of oil. Under high RPMs the oil presure can cause the piston to rise in the bore or "pump up". The more preload you give it the more the piston can "pump up" causing valve float. This is a simplified explanation as there is more to it. The lifter also has a check valve in it to control bleed off, but this should give you a general idea of what I'm referring to.

Chevy86 IROC-Z

iTrader: (17)

Got it. Thanx.

blackgold84

iTrader: (1)

if you do it runnig the motor, i have heard 1/4 to 1/2 turn...
i dont like messes tho, at tdc you can adjust half the valves, and @ 180 you can do the other half, no mess very easy.

Chevy86 IROC-Z

iTrader: (17)

Its an ugly mess. Ive done it a few times but with my OEM rockers. I got those little white oil plugs though to stop the squirt of oil.

So 1/4 - 1/2 it is. Thanks