I have had my heads off a couple times now and never had a loud valvetrain, but the most recent time when I rebuilt the motor....its loud. I have the comp cams type r lifters and hardened pushrods. Tightened all the rockers to 22 ft. lbs. and the valve train is still loud. Is there a different way to check preload or fix my problem? thanks

 

Checking lifter preload of LS1 non-adjustable rocker arms
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1. Turning the engine, bring the EXHAUST valve on one of the cylinders down until it is at peak lift (valve fully open). The pushrod will be pushed all the way down and the valve spring will be compressed.

2. Now, fully loosen the rocker arm bolt on the INTAKE of that cyl. (this valve will be fully closed).

3. Then turn that INTAKE rocker arm bolt down until the lifter is at "zero lash" (pushrod will start getting harder to turn when spun with your fingers while tightening the rocker bolt).

4. Mark the bolt with a marker.

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

From what I have read, the bolt should have turned between 1 to 1 1/4 turns for the acceptable GM lifter preload ... I was told that 1 full turn of the rocker bolt (past zero lash) equals approx .045” of lifter preload.

NOTE: You have aftermarket lifters. I understand that those like less preload than stock lifters. Instead of 1 to 1 1/4 full turns as indicated above, 1/2 to 3/4 turn may be more acceptable.

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

If you don't get the 1/2 to 3/4 bolt turn of preload with your Type R lifters, you need a different length pushrod.

Hope this may help,
Ron

 

What did you change in "the rebuild" of the motor? Cam? Lifters? What has changed since it was quiet?

 

All I did was install all of the rocker arms...tightened the nuts just snug then TQ them all to 18 pounds then went back and then to 22 pounds. I then turned the motor by hand with a socket on the crank several revolutions. Then I re-checked the TQ to make sure they read 22 pounds. I'm not saying this IS THE WAY to do it but is the way I just did mine. They are quieter than a church mouse.

 

If you torque a rocker down when its valve isn't closed, will there not be enough preload on it when it IS closed? Could this cause a slight tick?

 

Although the service manual recommends tightening the rocker bolt to 22 FT/LB when the valve is closed (less spring pressure on the rocker), it really is no big deal if it's torqued when the valve is open.

Bottom line; Tightening the rocker bolt has [no]effect on lifter preload. All the rocker bolt torque does is keep the rocker bolt from loosening up later and backing out.

Hell, you could tighten the bolt to 50 FT/LB if the bolt would not break in the process. Still would have no effect on lifter preload.

22 FT/LB is the torque spec that will keep the bolt tight, but not break it off. This is the same thing as with any bolt that holds something in place.

Ron,

 

In the rebuild I put new weisco forged pistons/ rings, all new bearings, arp rod bolts. Im not sure that the noise comming from the motor is definately valvetrain noise but the engine as a whole is louder. I did everything to spec when I was putting it back together. thanks I am going to be putting a different cam than what I have been running, so when I do this I am going to go over the preload on the lifters. thanks

 

I agree with Kimchee and Rice because when you TQ them you are really tightening the bolt down to the rocker arm swivel (for the lack of better word) then down to the rocker seat. 10, 22, 50 or so pound will still set it on the seat the same. Can seat it past the seat! If you don't go tight enough that's when you get a loud valve train.

 

2000 Camaro SS, You started out fine, but then you blew it. Ron's information is correct. Your last two sentences are misleading at best. You need to reread his second post beginning with "Bottom Line..."

Respectfully, Gary

 

</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by black98ws6ta:
<strong> In the rebuild I put new weisco forged pistons/ rings, all new bearings, arp rod bolts. Im not sure that the noise comming from the motor is definately valvetrain noise but the engine as a whole is louder. I did everything to spec when I was putting it back together. thanks I am going to be putting a different cam than what I have been running, so when I do this I am going to go over the preload on the lifters. thanks </strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">Changing to a different cam can create the wrong preload and cause lifter noise. When I went to the 01 LS6 cam I had more lifter noise due to the base circle being .032 diameter less than my stock LS1 cam. That gave me .016 less preload. My stock cam had a base circle of 1.552 and the 01 LS6 cam 1.520. I now have a Comp Cam with a base circle of 1.540 which yields a lifter preload of only .006 less than my stock. I have no noise now.

 

Larry is right. Here is something I wrote that may make all this cam base circle stuff become more easily understandable:
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The aftermarket cams being installed today will usually have a smaller base circle than the stock LS1 cam they are replacing.

Base Circle is actually the distance accross the cam's lobe. This is 90 degrees from the top of the cam's lobe at the point of highest lift.

You can easily measure this distance with a micrometer. Measure across the cam's lobe (the lobe's smallest distance across). You will find that it is 1.552” That is actually the cams “base circle”. You will need to cut this distance in half in order to get the cams "centerline to lobe heal" distance. The stock LS1 cam has a .776" centerline to lobe heal distance (19.7mm).

This centerline to lobe heal distance is what is important to you in determining lifter preload.

By the way, someone posted a while back that the TR-224 actually was measured to have a .030" smaller centerline to lobe heal distance than the stock cam.

If your aftermarket cam has lets say a .746" centerline to lobe heal distance, that would mean that it is .030" (30 thousands inch) smaller than stock. Remember, the stock cam was .776"

To be very accurate, you would then need a pushrod that is .030" longer than stock to achieve the same spec lifter preload as you had with your stock cam.

These aftermarket pushrods come in .050" length increments, so in this case, a longer 7.45" rod would get you closer to your factory spec lifter preload than using the stock 7.40" pushrod.

Remember, hydraulic lifters, due to there design have a + - preload variance that the lifter can operate within. It don't need to be exact. Just get it as close as possible with the various pushrods that are available (in .050" increments)

Be advised, milling the heads will change all this and require shorter pushrods equal to how much is milled off the heads.


So, to re-iterate all this:

1. If your cam has a .030" smaller centerline to lobe heal distance than stock, you would need a .030" [longer] rod.

2. If you just milled the heads .030", you would need a .030" [shorter] rod.

3. Combine the two, and your stock 7.40" pushrod would be perfect … It then becomes “tit for tat”

Hope this info helps a little.

Ron,

 

I didnt change anything cam or valvetrain wise this time. I just installed the forged pistons and apr rod bolts. The car never had this much valvetrain(or another noise) to it before. just dont know why the noise is here now and was never there the three other times ive put it back together.