caddy lifter preload - turns vs depth
Thread Starter
Le Mans Master
Joined: Nov 2009
Posts: 6,882
Likes: 234
From: Bangkok, Thailand
caddy lifter preload - turns vs depth
I have a set of the GM caddy lifter on my Cam Motion cam (.595 lift 220/230). The heads are new LS3's that have been cut .020" and I'm running .040" MLS gaskets.
I don't have a dial indicator, so I'm trying to figure out how many turns of preload I should use. I did ask Cam Motion and they suggested not more than half a turn, but that seems really low.
From what I can find, .060" seems to be the accepted amount of preload for them, but what does that translate to in turns?
Seems like I'd need pushrods that are about .040" shorter than stock. I do have a pushrod length checker but haven't gotten to where I can check it yet.
I don't have a dial indicator, so I'm trying to figure out how many turns of preload I should use. I did ask Cam Motion and they suggested not more than half a turn, but that seems really low.
From what I can find, .060" seems to be the accepted amount of preload for them, but what does that translate to in turns?
Seems like I'd need pushrods that are about .040" shorter than stock. I do have a pushrod length checker but haven't gotten to where I can check it yet.
Le Mans Master
Joined: Dec 2004
Posts: 5,492
Likes: 807
From: West coast CA
I have a set of the GM caddy lifter on my Cam Motion cam (.595 lift 220/230). The heads are new LS3's that have been cut .020" and I'm running .040" MLS gaskets.
I don't have a dial indicator, so I'm trying to figure out how many turns of preload I should use. I did ask Cam Motion and they suggested not more than half a turn, but that seems really low.
From what I can find, .060" seems to be the accepted amount of preload for them, but what does that translate to in turns?
Seems like I'd need pushrods that are about .040" shorter than stock. I do have a pushrod length checker but haven't gotten to where I can check it yet.
I don't have a dial indicator, so I'm trying to figure out how many turns of preload I should use. I did ask Cam Motion and they suggested not more than half a turn, but that seems really low.
From what I can find, .060" seems to be the accepted amount of preload for them, but what does that translate to in turns?
Seems like I'd need pushrods that are about .040" shorter than stock. I do have a pushrod length checker but haven't gotten to where I can check it yet.
Or spend a little more for some nicer calipers. They last forever and you can use them for everything.
Le Mans Master
Joined: Dec 2005
Posts: 6,999
Likes: 1,684
From: Southeast TX
On my LS3 with Caddy lifters, I have .010 head milling, .040 head gasket thickness, and 7.375 pushrods, I ended up with 2/3's of a turn to get from 0 lash to 22'#'s. Valve train is quiet and it revs freely to 7K rpm. Don't forget that the last little bit of "turn" doesn't increase preload, but only stretches the bolt. Sounds like you have the means to measure and get it right the first time. I'd do just that.
Race Director
Joined: Mar 2011
Posts: 13,262
Likes: 3,150
From: SW Florida
2021 C6 of the Year Finalist - Modified
That much plunger travel available within the lifter gives you a lot of adjustability ... if you wanted to install pushrods that actually center the plunger in the lifter's internal bore, that would be .100" (one hundred thousands)
I think around .060" to .080" is just fine for lifter preload when using these GM lifters.
Le Mans Master
Joined: Dec 2005
Posts: 6,999
Likes: 1,684
From: Southeast TX
I don't think the Caddy lifter will tolerate as much preload as the LS7 lifters. My initial preload was 1.67 turns or about .120" preload by Turbo6TA's chart. That was with stock length push rods. I had them "in stock" from a previous build so I tried them. It ran smooth and quiet, but just quit pulling at about 6200 rpm. I mean it absolutely wouldn't rev any higher. I knew that wasn't right with the cam and valve springs I was using. Ended up swapping in a set of 7.375" push rods and now it pulls effortlessly to 7K rpm.
I was told on another forum that valve train harmonics were to blame...not too much preload. Whatever it was, shorter pushrods (less preload) cured it.
I was told on another forum that valve train harmonics were to blame...not too much preload. Whatever it was, shorter pushrods (less preload) cured it.
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Melting Slicks
Joined: Nov 2011
Posts: 3,174
Likes: 259
From: Virginia
From all the reading of done on the Caddy lifters I believe I would shoot for somewhere between .060 and .080 preload on them. I’ve never personally used them tho. Rather than counting your turns I would just use the adjustable pushrod and get an accurate measurement
Thread Starter
Le Mans Master
Joined: Nov 2009
Posts: 6,882
Likes: 234
From: Bangkok, Thailand
I installed the 7.350 pushrods last night and closed up the valve covers. We'll see how it runs hopefully by the end of this month.