Z28GEN3

how do you lash a valve, is there a torque rating specified to tighten the rockers? what are the processes to do this?

Rocker arms are Comp Cams Magnum Roller tip. 1.6 ratio matched springs.

camaro03

from my experience, you get it to tdc adjust the valves that are closed, you should be able o tell, im not sure of which ones, then you turn it over to 180 out tdc and adjust the other ones.

when you adjust them, you want to tighten them down till you cant turn the pushrods, then a quarter turn more.

Me personnally i always do those steps then go over them when the motor is running, loosen them till they chatter then tighten them just a little past were they quiet down, you can buy oil clips from the parts store to make this a little less messy.

jamesbob02

NO DON'T DO THIS! I don't think he intended to mislead you, but DO NOT tighten until the pushrod cannot be turned. I think what he meant was to tighten until you feel a little RESISTANCE on the pushrod. This is "zero lash." And then a half turn is what's recommended. Tightening until the pushrod doesn't turn is WAY too far.

Again, I don't think he meant to say the wrong thing, but you just needed to know the right way before screwing something up.

camaro03

i used to work at a marina and thats what the mercruiser books say, you sure thats too tight? sorry if i misinformed, but thats what i remember and what i was told

jamesbob02

Are you sure it said to go til the rod doesnt turn anymore, or until it's feeling resistance from the rocker arm?

To be absolutely honest, I've never tried to tighten them that far. I did research before I ever did it, and came to the conclusion of the method I described. Also, I've read the "proper" way to adjust them, many times, here on the board, and I've seen more experienced guys than me say to not go that far.

I guess that makes me sound like a hypocrite for never actually going that far, but I'm just going off what I've heard from the more experienced, and am only trying to help. However, I'm absolutely sure that the right way is to find zero lash, and add a bit, not find "zero turn", and add a little bit. It may or may not screw something up, but depending on the extra turns it requires to get to that point, it could keep the valves from seating properly, which is not good. I've always adjusted mine the way I've said, and I know most other guys do too, so it works. I'm pretty sure the shop manuals say to tighten a little past zero lash, as well.

You might want to do some research here on the boards (search), and come to your own decision.

camaro03

just so you know i just went out and loosened all me rockers up, im in the middle of a motor install, its all new and i dont want to grind down a lobe from having my valves to tight during the 2000 rpm 20 min break in. They may rattle a little, but im planning on adjusting them while its running after break in anyway.

jamesbob02

Oh yeah I forgot to mention that too. Obviously you can screw up a cam too by tightening them down too much.

Z28GEN3

thanks for the replys guys
if theres anything else keep posting, cuase im planning on doing this in a few hours.

sqzbox

0* lash is obtained when there is no clearence between the rocker arm and the valve stem. What method you use is up to you as long the end results are 0* lash. Valves should be set warm, not cold, for final adj. Are you putting these on a stock cam & lifters? or after-market? You might look into getting a set of Poly-Locks also, that way you won't be under the covers every week or two readjusting them.

Slade1

When I did mine, I tightened down to a bit of resistance then tightened a 1/4 turn more. It takes awhile with this method because you have to turn the engine till the desired rocker moves up to TDC of that stroke I think. With a hydraulic roller though, it didn't exactly give consistent results for me. Some chattered from being loose, others were a bit on the tight side.

So I did the next thing I read on the boards, messy as hell, but worked like a charm.

I turned on the car and let it run, and loosened until it began to chatter, then I tightened oh so slightly till it stopped chattering and then gave it 1/4 turn more.

It's been more than a year now, no problems since that time.

sqzbox

Exelent! The end results are what your after. Some methods vary, I've tryed them all! If you don't mind getting some oil on you, I prefer the loosen, tighten method cause I sure don't want to hear them clatering when I'm driving! Whatever the feeler gauge says!

jamesbob02

This is the method I prefer as well because it is easier, and is actually more accurate - tighten til no noise, then half turn more. May not be the best way to do it "officially", but seems to work well for me.

Z28GEN3

it has all ready had the heads built for the cam swap. this is a Melling MTC-1 cam with the specs:

Degrees Degrees Inches Degrees
.050" Dur ADV. Dur. Valve Lift Lobe Cntr

Int. Exh. Int. Exh. Int. Exh. Int. Exh.
204 214 278 288 .420 .443 107 117


Non Roller. Hydrualic flat tappet. the camaro is a 1986 TPI 350 not original engine.

jamesbob02

I don't know what all the info was for, but basically the only thing imporant to know for this topic is that it is hydraulic, so you have to compensate for pre-load.

sqzbox

U soak lifters for preload, after it runs and oil pressure builds it's done! What's so tech about it? Tap Tap, no Tap, 1/4 turn! Hello?
U don't need a college degree to do that!

Z28GEN3

:hail: mighty one :yourock: know-it-all.

Error404

how does this method sound to everyone?

Bring #1 to tdc comp stroke and adjust intake 1-2-5-7 exhaust# 1-3-4-8 rotate one full turn and adjust intake#3-4-6-8 exhaust#2-5-6-7.


I did some searching on hotrodders.com, and this is the way they suggested.


any thoughts on that method?

jamesbob02

Yeah, that's the correct valve position to adjust each one (with the motor off), but you still have to know how to adjust it properly.

Error404

so, get the pushrods so that they touch the rockers (zero lash), and then 1/4 turn more. Break in the cam, then adjust the rockers so they don't clack when the engine is at idle? or is it 1/4 turn after they stop clacking?

sorry for the questions, I have just hear sooo many ways to do it.