Push Rod length and Preload on LS7 lifters
Push Rod length and Preload on LS7 lifters Would like people's opinion on what preload is good for a Blower cam and LS7 lifters.
With the shims required for the YT 1.7 roller rockers to get a center wipe on the valve stem... the pushrod checker ended up being 12.5 rotations and left just a tiny click with the rocker.
6.800" x (12.5 rotations x 0.050") = 7.425"
Which pre-load is better?
~0.075" preload requiring a 7.500" pushrod pn 7957-16
~0.050" preload requiring a 7.475" pushrod pn 7797-16
With the shims required for the YT 1.7 roller rockers to get a center wipe on the valve stem... the pushrod checker ended up being 12.5 rotations and left just a tiny click with the rocker.
6.800" x (12.5 rotations x 0.050") = 7.425"
Which pre-load is better?
~0.075" preload requiring a 7.500" pushrod pn 7957-16
~0.050" preload requiring a 7.475" pushrod pn 7797-16
Zero lash would be when there is no slack left in the rocker. From what I have read about LS7 lifters you should run about .080 preload (which is about half travel of the plunger inside the lifter) for a quieter operation. I started at .058 - .067 preload and I still had some lifter tick. Then I stepped it up to .083 - .092 and the lifter tick was gone.
Okay... I just checked the Intake valve and it looks like it needs more pushrod than the exhaust (another 0.025)?
looking at all the valves, it appears that the Exhaust has a higher stem vs the intake? wtf...
has anyone come across this issue?
looking at all the valves, it appears that the Exhaust has a higher stem vs the intake? wtf...
has anyone come across this issue?
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Verdad Gallardo I measured using a Comp cams checker pn 7702.
Cam is a Brute speed Blower cam.
To eliminate all the turns counting and confusion, I simply established 0 lash with the adj pushrod, removed it and measured end to end, added the desired preload, and ordered pushrods.
If going custom, you can get exactly what you want.
If buying off the shelf, might fall in between, so you have to decide less or more preload.
Alos, I noted at least on trick flow pushrods, they are .015" longer than stated when measured end to end. I just took that into account. I really think as long as you are between .050 and .080" preload, you are fine.
Clearly, the AFR heads use 2 different tip heights, so for sure, you will need 2 lengths.
Is my valvetrain silent? Nope. Too much spring for the LS7 lifters. I live with it. Compared to a solid roller....it's quiet!
Ron
If going custom, you can get exactly what you want.
If buying off the shelf, might fall in between, so you have to decide less or more preload.
Alos, I noted at least on trick flow pushrods, they are .015" longer than stated when measured end to end. I just took that into account. I really think as long as you are between .050 and .080" preload, you are fine.
Clearly, the AFR heads use 2 different tip heights, so for sure, you will need 2 lengths.
Is my valvetrain silent? Nope. Too much spring for the LS7 lifters. I live with it. Compared to a solid roller....it's quiet!
Ron
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From: MIchigan
The intake stem appears close to level with the retainer (may be the photo). Have you rotated the rocker through the entire lift cycle to check clearances with the retainer, etc.? I would do this with a check spring by hand.
Also, not sure how much shim you used but on my AFR's it took a 0.125" shim to get a good wipe pattern. The shims that came with the rockers weren't thick enough as the AFR valve stems were a little longer than stock.
Also, not sure how much shim you used but on my AFR's it took a 0.125" shim to get a good wipe pattern. The shims that came with the rockers weren't thick enough as the AFR valve stems were a little longer than stock.
The intake stem appears close to level with the retainer (may be the photo). Have you rotated the rocker through the entire lift cycle to check clearances with the retainer, etc.? I would do this with a check spring by hand.
Also, not sure how much shim you used but on my AFR's it took a 0.125" shim to get a good wipe pattern. The shims that came with the rockers weren't thick enough as the AFR valve stems were a little longer than stock.
Also, not sure how much shim you used but on my AFR's it took a 0.125" shim to get a good wipe pattern. The shims that came with the rockers weren't thick enough as the AFR valve stems were a little longer than stock.
Yes, shim was 0.110", however, this would vary due to valve stem height. The shims with the YT were definitely not enough.
Also it would mean i require a 7.550 - 7.600" rod. you cant buy 0.025" lengths after 7.500".
Good idea, the intake stem are closer, not sure if all clear the retainer, cycling will be a good idea.
Yes, shim was 0.110", however, this would vary due to valve stem height. The shims with the YT were definitely not enough.
Also it would mean i require a 7.550 - 7.600" rod. you cant buy 0.025" lengths after 7.500".
Yes, shim was 0.110", however, this would vary due to valve stem height. The shims with the YT were definitely not enough.
Also it would mean i require a 7.550 - 7.600" rod. you cant buy 0.025" lengths after 7.500".
Also, with a 0.110" shim, you will either need to provide a lot of clearance in the rocker covers or get 1/2" spacers. I am running a 0.125" shim and need to remove all the baffles an bosses inside the valve covers. It was a lot of grinding. If I had it to do over again I think I would have tried the 1/2" spacer first.
As far as pushrod length, you can get any length you want. Manton will make them easily and I would go to 11/32" OD as well. Note that Manton uses overall length for measurement. Trend will also make custom lengths and was where I got my 3/8" double taper pushrods. I wouldn't worry about the final length, you can get whatever you need just not from the vendors who only stock off the shelf sizes.
