TNT_Z28

i just installed a set of roller rocker arms and want to make sure i preloaded the lifters correctly...

-concentrating on one cylinder at a time (intake and exhaust), i rotated the crank by hand until one of the valves was closing.
-i then tightened the opposite rocker arm while swiveling the pushrod between index and thumb. when i felt tension, i then tightened an additional 1/2-3/4 of a turn. then tighten the set screw
-rotated the crank again and did the same the for the other valve.
-then repeated the process for every other cylinder.

this is the first time I've gone valve by valve. in the past I've always just followed the method described in the Haynes manuel. so im just looking for conformation for peace of mind.

eseibel67

Procedure is good, except you said "rotate crank until one of the valves was closing". The exhaust valve moves first, then the intake. Make sure the intake valve is fully closed so that the cam is on it's base when you are setting the preload. Then you can do both at once on the cylinder and only rotate the crank 8 times instead of 16.

There is an even better procedure whereby you can adjust 1/2 the valves, move the crankshaft once, and then adjust the other 8.

sofakingdom

iTrader: (1)

THINK about an engine cycle for a minute....

If you do as described, i.e. adjust ing each valve just as the one for the other cyl is closing, you will be adjusting the intake as it's already starting to open; since "just as the exh is clsoing", is TDC, and the intake opening.

Reason through the entire engine cycle and several RIGHT ways to do this will occur to you, which what you described is NOT one of.

The intake is fully open about halfway trhough the intake stroke (duh)... at that point, the lifter is on the "nose" of the lobe, which is EXACTLY OPPOSITE the "heel" which is where you want to set it for adjusting it... therefore the correct point to adjust it is when the engine is exactly one full crank revolution, which is 2 out of the 4 cycles, away from the middle of the intake stroke. 2 strokes away from there the other half of the int stroke, the compression stroke, and about half of the power stroke; since the exh valve starts to open as the piston nears the bottom of the power stroke, exh opening corresponds to ½ of the engine cycle away from the peak int opening, which is directly opposite the "nose" of the int lobe, which is of course the heel of that lobe. Likewise, the exh is fully open about halfway through the exh stroke (duh again).... and 2 full strokes away from there is the other half of the exh stroke, the full int stroke, and about half of the comp stroke. Since the int closes sometime shortly after the beginning of the comp stroke, there's your slignment point for exh adjustment: just after the int valve closes.

The "Chilton's" method of putting the engine at one place and adjusting half of them, then rotating it one full turn (½ cycle) and adjusting the rest, is ONLY good for the lamest of the lame stock cams, and for when you want to use SO MUCH preload that the ¼ turn or more of inaccuracy in it, is swamped by your preload. I would NEVER use that on any engine that I actually cared about.

One correct procedure is the "EOIC" method. In this, you adjust the intake for each cyl just as that cyl's exhaust is just barely beginning to open; and you adjust the exhaust just after that cyl's intake has closed. Easiest way to do this is to find one of those points for one kind of valve, and then just go through the firing order one cyl at a time, rotating the crank exactly 90° from one cyl to the next; then repeat for the other kind of valve.

THe MOST ACCURATE way is to realize that one cyl is doing THE EXACT OPPOSITE, i.e. exactly ½ engine cycle, of what the cyl 4 cyls away from it (one full crank rotation) in the firing order is doing. For example, when the #1 intake is fully open (on the "nose" of the lobe), the #6 intake is exactly on the "heel" of its lobe, and is ready to be adjusted. So, find the peak opening of a valve, then go through the engine and do that same kind of valve on the cyl 4 cyls away in the firing order, one at a time through the firing order as described above, then repeat for the other kind of valve.

"Feel tension" is wrong also. That will end up making the valves too tight. Instead, jiggle the push rod up and down while tightening the rocker; as you get close to zero lash, there will be less and less jiggling available; at the point where the jiggling just disappears, you are at zero lash. From there, add your desired preload.

And of course, no matter how bad you screw it up, as long as it's not so bad that the engine can't run, you can alwways go back and re-do them with the motor running, by backing each one off one at a time until it just begins to clack, then tightening it until it just shuts up, and go through the whole motor this way; then shut it off and add your desired preload to each one.

TNT_Z28

Thank you. I couldn't find the procedure described in detail when I used the search function earlier, and I figured I was doing it wrong which is why I posted. Thanks again.

TNT_Z28

Thats the procedure that makes the most sense to me, so thats the on I used. i also used the jiggling method instead of the tension method as suggested.

the problem i ran into is when i started the motor, there was obvious loud clacking coming from the majority if not all of the rockers. its very hard to determine which are making noise and which aren't. so i snugged each nut up slightly until the only clacking i could here is if i had my ear 6 inches or so away from the rockers.
(which leads me to ask... is there always going to be a little bit of noise?)

thats seems logical, but i dont know if its really that practical, seeing as oil gets sprayed everywhere and its hard to here over the cooling fan and exhaust.

whats frustrating me now is...
-i dont know now how tight or loose each individual arm is or isn't. (im thinkin ill just start all over tomarrow)
-when i try to adjust with the engine running, oil gets everywhere, including the headers, which start to burn and smoke (and is more irritating than anything)

and i guess now is as good of time as any to ask...
1) what are the consequences of having the rockers too tight or too loose?
2) this seems like a lot of screwing around. am i making it more complicated than it is, or is it one of those things that gets easier each time you do it? (i dont mind putting in the time and effort. im just used to the Haynes manuel way)

samiam91RS

so what happened? did you ever figured out a better way since everyone dipped out on ya?

sofakingdom

iTrader: (1)

From where you are now, do it with the engine running. The best way.

Run all 16 as fast as you can, with the motor running; THEN AND ONLY THEN, shut it off and add your desired preload AFTER you shut it off. That'll reduce the time spent with it running to about a third of what it would otherwise be.

Also, it's basically IMPOSSIBLE to tighten the Allen set-screw enough to keep em from backing off. THerefore tighten them that way as tight as reasonably practical, without any significant effort; then tighten the Allen and the Poly-Lock TOGETHER to about 15-20 ft-lbs on the nut. Don't get too aggressive with that or you'll split the nuts.

Next stop... the quarter car wash.