Correct pushrod preload?

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trbodrt

trbodrt

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Used the search feature and finding different answers. I'm running a compcams hydraulic flat tapper lifter xe275hl cam. I converted my lifter to a solid by taking apart and shimming the inside. This is going in a stock stroke 360 for street use and was wondering after I set my adjustable pushrod length to 0 preload how much of a theoretical turn should be made and about what that equals in additional length so I can calculate what length pushrods to order. Thanks guys.
 
If you turned your hydraulics into solids you don't want any preload. You want to have a gap. If I remember correctly the gap on the intakes is .018 and the gap on the exhausts is .026. That is not gospel. You will have to get the answers on the gaps from somebody that knows more about it than me.

Jack
 
I believe he made one or two solid just to check pushrod length if he was running solids on a hydraulic cam - which can be done - I'm thinking the lash would around .010 and I think but don't quote me preload is around .030
 
Yeah, I just converted one to solid to check for pushrod length and it will then be converted back to hydraulic.
 
Extend to zero lash, remove, measure and add whatever length you want as preload.

1/4 turn on adjuster usually = ~.010

I run a bunch of stuff with only 1/4 turn preload when using adjustable rockers and hyd lifters. Lots like 1/2 turn. Some places suggest a lot of preload, not for my stuff.
 
Thanks crackedback! I think I'll try the 1/4 turn when it comes time to adjust. So I'll be ordering 10 thou Longer push rods from 0 lash. How many threads do you like to have coming out the bottom of the rocker?
 
You will need at least 5 threads on the bottom showing. I have always used 1/4 turn down from 0 lash on hyd lifters. In my opinion, it helps at higher RPM's.
 
You have adjustable rockers?

Get the proper number of threads showing below the rocker body and then measure using the adj pushrod. I like to go on the minimum amount of threads showing out of rocker body. Too many threads and the adjuster get levered and more susceptible to breaking.

Measure both sides, they aren't always the same.
 
crackedback said:
you have adjustable rockers?

Get the proper number of threads showing below the rocker body and then measure using the adj pushrod. I like to go on the minimum amount of threads showing out of rocker body. Too many threads and the adjuster get levered and more susceptible to breaking.

Measure both sides, they aren't always the same.
Click to expand...

this
 
I would lock the hyd cup .020" below the snap ring (this is a good preload amt & this duplicaes the actual running setting plus SB pushrods are at a severe angle so even more I would want to duplicate the actual conditions). I'd want 1&1/2 threads below the rocker (MP has a 9/32" dimention from the rocker to the ball tip. With all those settings in place then adj the checking pushrod to get the right length. In addition I would also first check the wipe pattern and the end view & see how close the rocker arm/pushrod is to a right angle at 60% of cam lift (iirc it's 60% for a SB/50% for a BB you might check Hughes engines site for confirmation). coil bind/retainer to seal/rocker to retainer clearances/piston to valve: "clearances"
 
trbodrt said:
Yeah, I just converted one to solid to check for pushrod length and it will then be converted back to hydraulic.
Click to expand...

Sorry about that trbodrt. I read preload on a solid and saw wiped cam. Just trying to help to fast I guess. The quarter turn = .010 sounds right to me. That is where I ran my 360 before building the 340.

Jack
 
oldkimmer said:
............... 1 1/2 to 2 threads showing is plenty anymore than 3 and ur asking for big trouble..........kim............
Click to expand...

THIS! --- ^^^^^^^

1-1/2 - 2 threads showing is it!
5 is way to much! Mitch! Re-do your pushrods!

Useable plunger area is the first and last .010. Of plunger travel. Better to have a little more than a little less. You don't want to run it to close because you do not want the plunger to travel fully closed or depressed all the way down. This will damage the plunger. You do not want a litter coming apart in a running engine.

A little extra preload is not the end all.

Cracked runs it close, Rapid Robert runs it in a safer zone and still has some room.
 
Haha! No worries Cotote Jack. Thanks for all the help, that's why I love this site, having awesome mentors at the click of a button. Even though I'm a mechanic by trade I feel like I'm going through my mopar apprenticeship. Thanks again.
 
i read a test in one of the muscle mags on different pre loads but 1/4 to 3/4 turn was best.They checked some factory stamped rockers that were as much as .100
 
That's interesting ir3333, I guess that's the good thing about hydraulic lifters that's it's not an exact science and a bit of room for error.
 
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