I am in the process of installing the compcams shaft mount rockers (1.8's). I know that shorter pushrods are necessary, and I will be using a pushrod checker to determine the correct pushrod length, however I wasn't sure if the length should be checked with the hydraulic lifters collapsed or full?
Thanks.

 

Anybody?

 

Neither.
You need to get the lifter for the cylinder your checking on the base circle(low point on the cam). Slowly tighten the rocker bolt while spinning the pushrod between two fingers. Need small fingers. When the pushrod just makes contact that's your start point. Tighten the rocker bolt until it is tight. 22lbs of torque if you're not sure. As you're
tightening count the number of turns to the bolt seating. 3/4 turn to one turn is ideal and should give you about .060 preload. Your adjustable pushrod will help determine the length pushrod needed to achieve the currect number of turns and translate to pushrod length.
I had a hard time with the adjustable pushrod, because when you spin it the adjuster changes. Rocking the rocker arm works too.

 

Try the following:

http://www.holley.com/HiOctn/TechSer...ECVTTech1.html

 

Brent, you realize that the link is for determining if geometry is correct after the PR length has been established?

 

Thanks gojo,
but the rockers are a shaft mount. I understand how to adjust the rocker lash. What I was inquiring about was wether the lifters needed to be bled or pressurized to determine the proper pushrod length.
Thanks.

 

I was told that geometry was an important part of determining push rod length.

 

It doesn't matter if they are shaft mount.
I described the method for determining PR length. If you know how to get lash then you know how to get length. If you have too many turns to bottoming out then the PR is too long. If you have to few then the PR is too short.

 

Thanks Brent,
I agree geometry is important, however I am simply asking if the pushrod length is determined with the lifters bled or pressurized.

 

You are asking the right question, zero lash on a unloaded lifter and zero lash on a pre-loaded lifter are two different things. I learned that when trying to adjust my Comp pro-magnums.

You really need to hear this from a pro, but my guess is you need to do this with the lifter pre-loaded.

And getting this information is SOOOOOO easy call Comp's tech line. Just explain it to them and they will tell you exactly what you need to do. Trust me it's worth it even if you have to spend some time on hold.
CAM HELP: 1-800-999-0853 (it's help for any of thier products really, not just cams)

 

You are asking the right question, zero lash on a unloaded lifter and zero lash on a pre-loaded lifter are two different things. I learned that when trying to adjust my Comp pro-magnums.

You really need to hear this from a pro, but my guess is you need to do this with the lifter pre-loaded.

And getting this information is SOOOOOO easy call Comp's tech line. Just explain it to them and they will tell you exactly what you need to do. Trust me it's worth it even if you have to spend some time on hold.
CAM HELP: 1-800-999-0853 (it's help for any of thier products really, not just cams)

Good Luck!

 

The lifter seat is always at the top of the bore(as long as no pressure is applied to it). So there is always some tension pushing it up, just more when it pressurized(car running). Like gojo said “When the pushrod just makes contact that's your starting point” or Zero lash.

 

Thanks IFLUBYU,
Thats exactly the problem I was anticipating. It seems every time I ask somebody in regards to either bled or pressurized lifters, they go on a tangent about something else. When I checked the pushrod lengths, I noticed a distinct difference between pressurized height and bled height. Thanks for the ph. no., I'll give compcams a call in the morning.

 

One more try.

3. Back off the intake rocker arm adjuster and remove any tension from the pushrod. Wait a minute or two for that hydraulic lifter to return to a neutral position. The spring inside the lifter will move the pushrod seat up against the retaining lock if you give it time to do so. (If you are installing brand new lifters they will be in the neutral position when they come in the box.)[IMG]3. Back off the intake rocker arm adjuster and remove any tension from the pushrod. Wait a minute or two for that hydraulic lifter to return to a neutral position. The spring inside the lifter will move the pushrod seat up against the retaining lock if you give it time to do so. (If you are installing brand new lifters they will be in the neutral position when they come in the box.)[/IMG]
There is no difference bled or not. If there is you have bad lifters or you have put a load on the lifter. Go get a lifter and try pushing down on the seat. You will be surprised at the pressure the spring exerts. Nobody is going on a tangent. You are not understanding everyone who tries to explain.

After the call to comp. please post the answer.

IFLUBYU There is no such thing as zero lash on a preloaded lifter.

 

hightest - I'm not tyring to argue here. But, gojo and brent 02 are not heading on a tangent to your subject.

Take apart a lifter and examine it . The spring maintains pressure on the back of the lifter seat (cup) - as brent said. As gojo said - as long as you don't exceed the pressure of this spring you wil have the max length of the lifter. The .060" preload gojo is referring to translates, geometrically, to the range (midpoint) of acceptable movement of the seat within the lifter bore.
You can go to Yella Terras website and download their Install Instructions and Tech Tips. If I remember correctly there is a tech sheet on determing proper PR length that basically follows gojo's and brent 02's suggestions.
FWIW.


***OOOPS...darn I'm slow!! gojo posted in the Time it took me to write the above!!!

 

Brent, you are right. However, it's likely the geometry will be okay if the correct length pushrods are used. Nothing radical has been done to the heads or valvetrain and the rockers are designed by Comp for the car.

 

Yes, I agree. Sorry, I was just basing all of the above by my own experiences with head/cam/rocker arm swaps

 

Hey Guys,
I wasn't referring to to your replies in regards to going off in a tangent.
If you notice, I said that "whenever I ask", as in the verbal sense. I had contacted a couple of speed shops, and a GM dealer with the same question, and none of them had any answers, they would only talk about how shaft mount rocker systems were never designed for use in the LS1 engine and that I was better off staying with stock rockers for longevity. That was what I was reffering to when I said "tangent".
I apologize if you think I was reffering to Gojo & Brent02.
I didn't mean to offend anyone here. I appreciate all of the replies.
By the way, I spoke to someone at Jesel (CompCams is closed for the weekend). Jesels' reply is, yes there should be enough spring pressure within the lifter to properly check your pushrod length without oil pressure in the lifter; however the GM lifters are not of the highest quality and it would be prudent to do the length check as soon as possible after the vehicle has been run as the added pressure may help compensate for any weak lifter springs that may be present. They also suggest checking the lengths at at least 3 pushrod locations in case one weak lifter provides an erroneous reading.
Thanks again for the replies.