Sorry, another preload question
Thread Starter
Teching In
Joined: Dec 2004
Posts: 24
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From: Atlanta
Sorry, another preload question Here is what I have- heads are not milled, block is decked
.005, and I have a Comp Cam ( a little different base circle
than stock) I am using a set of 7.4 pushrods and Jessel SS
non-adjustable rockers. I am using new Comp 850 lifters.
I marked the tip of the valves with a marker, installed the
valve train and rotated the motor a few times. When I removed
the rockers, the mark on the valve was very thin ((1/32") and
right in the middle of the valve. Seems perfect to me.
Now my stupid question....If the geometry is good, how do i
know if the preload is correct? I can't spin the pushrods because
the clearance is too tight. Do I need the setup a dial indicator
on the assembled rocker and no preload, then torque the shafts
down and measure the rocker movement? Or should I be O.K.
with what I have already checked?
Thanks!
.005, and I have a Comp Cam ( a little different base circle
than stock) I am using a set of 7.4 pushrods and Jessel SS
non-adjustable rockers. I am using new Comp 850 lifters.
I marked the tip of the valves with a marker, installed the
valve train and rotated the motor a few times. When I removed
the rockers, the mark on the valve was very thin ((1/32") and
right in the middle of the valve. Seems perfect to me.
Now my stupid question....If the geometry is good, how do i
know if the preload is correct? I can't spin the pushrods because
the clearance is too tight. Do I need the setup a dial indicator
on the assembled rocker and no preload, then torque the shafts
down and measure the rocker movement? Or should I be O.K.
with what I have already checked?
Thanks!
If you want to know for sure, use the dial indicator. It's good practice and you will know the real preload value. If you run into other problems, you will be able to rule out preload since you already measured it. Just make sure you check 3 or 4 rockers to verify your numbers are consistent.
You dont have to worry about preload with the SS series rockers as they are non-adjustable. Just follow the Jesel directions and use the adjustable pushrod that came with them. Shim the stand if required...
Thread Starter
Teching In
Joined: Dec 2004
Posts: 24
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From: Atlanta
Originally Posted by xssive
You dont have to worry about preload with the SS series rockers as they are non-adjustable. Just follow the Jesel directions and use the adjustable pushrod that came with them. Shim the stand if required...
the preload to see if my push rod lenght is correct. I was plaaning to
get the correct preload by using different push rods, not by shimming
the stand. I didn't get an adjustable pushrod with the rockers.
Thanks!
The adjustable pushrod should have been included with the rockers. I agree that you should change the pushrod length accordingly, but the shims are nice for temporary adjustments. You sound good to go with your setup though if the rocker tracks straight in the center. The Comp 850 lifters are pretty forgiving with the preload as far as I remember...
TECH Resident
Joined: Jan 2003
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From: AUSTIN TX
Unfortunately you can not adjust the valvetrain geometry on the LS1 with out going to an adjustable valvetrain. The reason for this is obvious, you can change the valvetrain geometry by using different length pushrods, but if you have to adjust the preload by using different length pushrods then you are stuck with the pushrod, that gets your preload correct. Of course you could pull the heads and change the valve stem heights by either grinding the stems (to shorten the stem height) or replacing the valves with longer ones or sinking the valve seat (to increase the height), but then of course you would be changing the lifter preload when you do any of those which would then require different pushrod lengths again to get that right, which would alter the geometry again. Basically what I am getting at is your geometry should be pretty damn close if the heads were built by a reputable shop that knows about where the stem height should be, so just alter your pushrods to get the lifter preload set and be done with it. Or by a good set of the Jesels that are adjustable. Then you can use pushrod length to correct for geometry and adjust the rocker to set preload.
I agree with all of this, but why guess? It's not that hard to set up the dial indicator (DI) and find out the REAL value instead of wondering if your setup is ideal. With non-adjustables rockers, the only way to vary preload is with your pushrod length, so why not determine which pushrods are best? Even with an adjustable pushrod, you still have to use the DI to determine the preload.
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TECH Resident
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From: AUSTIN TX
Originally Posted by Byter
I agree with all of this, but why guess? It's not that hard to set up the dial indicator (DI) and find out the REAL value instead of wondering if your setup is ideal. With non-adjustables rockers, the only way to vary preload is with your pushrod length, so why not determine which pushrods are best? Even with an adjustable pushrod, you still have to use the DI to determine the preload.
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Teching In
Joined: Dec 2004
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From: Atlanta
O.K... here is what I came up with.
I used a dial indicator to check the preload. I checked the
preload on 1,2,7,8 With the Jessel SS torqued to spec I came
up with .065 on #1, .110 on #7, .120 on #2, and .115 on #8.
What should the correct preload be on the Comp 850's? Comp
told me .030-.050, but that doesn't seem right.
Thanks!
I used a dial indicator to check the preload. I checked the
preload on 1,2,7,8 With the Jessel SS torqued to spec I came
up with .065 on #1, .110 on #7, .120 on #2, and .115 on #8.
What should the correct preload be on the Comp 850's? Comp
told me .030-.050, but that doesn't seem right.
Thanks!
TECH Resident
Joined: Jan 2003
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From: AUSTIN TX
Originally Posted by axer
O.K... here is what I came up with.
I used a dial indicator to check the preload. I checked the
preload on 1,2,7,8 With the Jessel SS torqued to spec I came
up with .065 on #1, .110 on #7, .120 on #2, and .115 on #8.
What should the correct preload be on the Comp 850's? Comp
told me .030-.050, but that doesn't seem right.
Thanks!
I used a dial indicator to check the preload. I checked the
preload on 1,2,7,8 With the Jessel SS torqued to spec I came
up with .065 on #1, .110 on #7, .120 on #2, and .115 on #8.
What should the correct preload be on the Comp 850's? Comp
told me .030-.050, but that doesn't seem right.
Thanks!
Last edited by BOWTIE; Apr 5, 2005 at 06:35 PM. Reason: additional info
Thread Starter
Teching In
Joined: Dec 2004
Posts: 24
Likes: 0
From: Atlanta
I removed the rockers and re-checked everything again and
I may have found the problem. I used new lifter trays and they
hold some of the lifters pretty tight. I found out I needed to push
down on the rocker to make sure the lifter was seated on the cam.
These are my new measurements :
#1 I- .080
E- .055
#8 I- .075
E- .065
#7 I- .085
E- .060
#2 I- .080
E- .080
Does this much variance seem normal? I called Comp again and a
different tech told me .030-.080 is normal. If the rest fall in the same
range, should I get some 7.375 pushrods?
Thanks!
Russ
I may have found the problem. I used new lifter trays and they
hold some of the lifters pretty tight. I found out I needed to push
down on the rocker to make sure the lifter was seated on the cam.
These are my new measurements :
#1 I- .080
E- .055
#8 I- .075
E- .065
#7 I- .085
E- .060
#2 I- .080
E- .080
Does this much variance seem normal? I called Comp again and a
different tech told me .030-.080 is normal. If the rest fall in the same
range, should I get some 7.375 pushrods?
Thanks!
Russ
Last edited by axer; Apr 5, 2005 at 08:25 PM. Reason: spelling