It looks like I might end up going with a set of Yella Terra rockers and am curious as to the proper install methods for these rockers. I know the torque spec is 22 lb/ft but I am seeing alot of talk about preload/shim's, etc.


Any info would be great. Just want to make sure I am not missing anything.

Thanks.

 

http://ls1howto.com/index.php?article=21

 

A blurb from the site above:

[quote]
You want the smallest number of turns you can get, as long as you have at least 1/4 or 1/2 full turn of preload in there once you are all setup. If you get to the point where the bolt is tight yet you can still spin the pushrod (without using shims), then your pushrods are either too short, your valves are too short, or you have some strange valvetrain geometry. You MUST have some preload or it will be OBSCENELY loud and run very poorly. Longer pushrods may fix your issue in this case.

Now that we know if you need the shims or not, we don't need to do ANY of that legwork above on the other 7 cylinders...we can just throw the rockers on and go (either using the shim or not, depending on what you found out above). So, do just that....bolt up all the other 7 pairs of rockers (if you have ported heads, you may want to use a little locktite on the bolt threads). Remember, since these other cylinders are in totally random positions, it is 100% normal for the rest of the rockers to compress some valve springs as you start to tighten the bolt down, since these valves aren't all shut. Using a small socket wrench, tighten all these bolts down. You should be able to feel when the rocker seats itself as the bolt will stop turning if you are using a small socket wrench [/quote}


Could somebody explain this a little further. Everything else seems crystal clear to me except this part.

Once I install the first set of rockes over the closed valve - it says to hand tighten them with my fingers. Then use a socket to make 1/4 turns from the 12 o'clock position to preload everything. How do you know when you put enough preload on it. It says to alterante between each rocker on the set back and forth but to what point? How do I know if I only need 1/2 turn on each or more?

Then once I have installed the first pair - can I just throw the other sets on as is? How do I know how tight to make them especially on the springs that arent a full height? Would it just be tightening them up to 22 lb/ft? I guess I am confused as to why you would preload one set and then just use 22 lb/ft on the others?

 

Can anyone further explain this?

 

Checking Lifter Preload (non-adjustable rocker arms)
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1. Turning the engine, bring one of the cylinders to TDC on the compression stroke. Both valves will now be fully closed on that cyl.

2. Now, fully loosen one of the rocker arm bolts on that cyl.

3. Then start turning the rocker arm bolt down until the lifter is at "zero lash". You will be able to tell it is at zero lash when the rocker bolt gets very hard to turn. It gets hard to turn because the valve spring starts to compress. Again, stop turning the bolt as soon as you feel resistance to turning. You can also spin the pushrod with your fingers while turning down the bolt. You will feel resistance to spinning when you are at zero lash.

4. Then mark the bolt with a marker.

5. Now count how many turns it takes to completely tighten the rocker bolt to 22 FT/LB.

The bolt should have turned between 1 3/4 to 2 turns for the acceptable GM lifter peload. This is how much preload a bone stock LS1 will have.


NOTE: You really only need to do this on one cylinder. The rest will be the same.

NOTE: If you have aftermarket Comp Cams “Type R” lifters, I understand that those like less preload than stock lifters. Instead of 1 3/4 to 2 full turns as indicated above, about 3/4 to 1 turn may be more acceptable.
Yella Terra rockers may also use less preload too. Just remember, no matter what hyd lifters or rocker arms that you have, you must have [some] preload.

NOTE: Allways run the engine prior to checking the preload so as to get the lifters pumped up. This is important if you just installed new lifters or had the old ones out while installing a new cam.
_______________________________________________

Hope this will help to clerify this a little....
Ron,

 

Yeah I think it does. Basically I use the first two as a guide. If I hand tighten down to zero lash and it take 1.5 full turns to hit 22 lb/ft - then I can just hand tighten the rest down to zero lash and then turn the same amount of turns as needed on the first set. Sounds easy enough.

 

I think you are looking at this the wrong way.

This procedure only allows you to see how much preload you actually have. It does not allow you to actually set the preload. You don't have ajustable rocker arms. You cannot "just hand tighten the rest down to zero lash and then turn the same amount of turns as needed on the first set".

All rockers need to be torqued to the spec of 22 lb/ft.

If you want to actually change the lifter preload, you will need to either install shims under the rockers or change the pushrod length.

 

I don't like that much preload. I use 0.5 turns in my engine.

 

As you turn in the rocker bolt, at some point the spring will start to compress; start counting turns here. You keep turning it and at another point, the bolt will bottom out because the rocker pedistal will be all the way against the head; stop counting here and put the final torque on the bolt. I got 5/8 of a turn and have zero valvetrain noise. BTW, Yella Terra's are supposed to be torqued to 25 lb/ft; stock rockers are 22 lb/ft. Be sure to clean the bolts first with carb cleaner or acetone, then put Locktite under the bolt head. Also, when removing the old bolts, use an 8mm black impact socket as you will likely break an ordinary socket.

 

***Head hurting***

Sad part is that I am an engineer - so you would think that it would make SOME sense lol.

Ok - let me see if I get this know - and please refrain from smacking me in the head if I still am not getting it.

Hannibal <---- new to wrenching on his own car

Ok - couting the turns on the first set is more or less just to check preload to see if you need to shims or not (with YT's). If you get more than 2 turns or so - then add shims. After that the rest can go on and torqued down to 25 lb/ft regarless of valve position on the particular valve?

 

Bingo!

You got it. All you are doing is checking one cylinder to see how many turns of preload it has. All the rest will be the same. If you are happy with the preload, just make sure all rocker bolts are tightened down to the correct torque before you button the motor back up.

If you don't like the results, add shims or change pushrods on the cylinder you are checking. Check it again. If it's then ok ... Add shims or change pushrods to the rest of the valves so they will be the same too.

Just make sure that after your done, all the bolts are tight (22 lb ft)

Ron,

 

Tin Indian ..... 25 lb/ft for YT's <--- Hannibal's been reading

Thanks alot for the help and patience

 

I've installed a few sets and I use 22 all the time. If it was good enough for GM, its good enough for me. You can do 25 if you want, but I'd rather go by the GM spec (and thus, that is what I recommend on my site). Its still the exact same stock bolt in the exact same stock hole.

 

Might want to rotate the engine and torque when the valves are closed, read the post about a broken rocker arm? Sickening to think that the bolt could break from the tension on the spring as your tightening, and bending the bolt to point of failure. Just a thought, only takes a minute, and could save a lot of time.

 

Good point. In fact, once I tightened my rockers to the required torque, I just turned the engine a little and re-torqued the bolts. Did this a couple of times to insure the springs were in there least compressed position at least during one of the re-torques.

I will say this, once they were initially torqued, nothing really changed during the other re-torques with the motor turned at various positions ...

But ... Still a good idea.

 

Cat3:
I beleive we did the terra yellows in my car tightening the rockers one-by-one when both valves were closed. this requires you to turn the engine a few times with a breaker bar...

I started to tighten the arm on one cylinder with the valves open and the bolts got cocked....we wnet to this method as a precaution and it worked great...

JMX says he has done a bunch of these without turning the moter with no problem but, why take a chance....many here have broken/bent rocker bolts.....

 

Is it really needed to check lifter preload with just a cam install and reinstall of stock rockers? Would it be OK to just torque them the 22, spin the motor and recheck the 22? Thanks!

John