Just starting to assemble my 416”. I have the Comp 15956-16 short travel hyd roller lifters. Anyone knows the preload in inches (or mm) measured on the rocker arm (pushrod end). The instruction only says zero to 1/4 turn but that depends on thread pitch and if you have pedestal bolt or adjustable pushrod cups. I have the Jesel Mohawk rockers.
Thanks.

 

¼ turn on a 1mm or 24 tpi bolt at the rocker fulcrum would be about .016" at the push rod with 1.7 rockers. Which would be a "typical" thread for most engines with adjustable rocker systems.

Sounds to me like they want 0 - .016" of preload, more or less. I might shoot for something like .010". If those rockers have an adjuster, see what thread it is, set it to zero lash, then turn it enough to put .010" more on the push rod. If the adjuster is also 1mm or 24 tpi for example, then 1 turn is about .040"; ¼ turn on the adjuster would be just about .010".

 

Good info. IIRC thread pitch on the rocker bolts in LS is 1.25-mm, to figure.048 per rev on the bolt threads and .076 at the pushrod. Splitting hairs at 1/4 turn for sure, though.

 

On Summit's website, there's a Q&A for this part number where someone said they contacted Comp with the same question and they got a recommendation of .020-.030" of preload. If I were you, I would call Comp and see what they say.

 

Ok, I’ll call Comp. Thank you all three.

 

0 preload is a bad idea on a hydraulic. The preload will loosen up about .008-.010 when the motor heats up.

What I’ve seen with short travel lifters is yes typically you are recommended minimal preload, but for a hydraulic you need to keep preload on the plunger always.

Preload it down .015-.025” cold and call it a day.

 

Yea, just called Comp and they told me to set .010”-.025”. I’ll go for something in between.
Here is the instructions for the 15956 lifters. Zero to 1/4 turn.

 

I have a set of Morel .040 travel (verified) lifters going into my LS7 build. I'm checking all 16 rockers and will be using two different pushrod lengths to fit the intake and exhaust base circles of our SUM-8721 Saturn Stage 5 cam. I'm shooting for .030 preload to keep it out of negative lash as the block grows. This isn't easy, but it is made easier with the Comp XD-A 2 piece shimmable pushrods (CCA-896806-KIT in my case).

 

I have been thinking of this for a while now, maybe I don’t interpret the instructions correct (my native language isn’t english). Does CC say to set a 1/4 turn after zero lash, would make more sense.
What do you guys think?

 

Yes.

Between zero lash, and ¼ turn of preload.

This should ALWAYS be done HOT on any tight-lash kind of setup, to take the metal expansion variable totally out of the picture.

And since those appear to be rather "generic" instructions, without any consideration of engines like LS that don't have adjustable rocker arms, that ¼ turn spec is still going to be referenced to a 24 tpi thread, which is just over .040" per turn; .010" would be ¼ turn; with the rocker ratio, that puts ¼ turn at just about .016" at the push rod; therefore a push rod selection giving preload anywhere in the .010" ± .005" range should be totally fine.

 

That’s pretty much my conclusion also. I have been measuring all day and came up with 7.850” and I was a little suprised of the length. Measured all 16 twice and they are within .010.
The 7.850” is without preload and the adjuster half a turn out from bottom so I’ll end up with approximatly one turn out and that’s where I want to be. Jesel recommends not more than 2 turns out if possible.

 

If you have to set the lash cold you can factor in like .010 expansion in an all aluminum block/head situation of like .005 for just aluminum head - or something like those numbers. I think Comp Cam or someone like that has expansion rates numbers as general rules of thumb. So a preload of .020 cold would turn into a hot preload of .010 in an all aluminum situation as the aluminum block and head would expand more than the steel pushrod. Come to think of it Manton pushrods would also know the answer.