correct lifter preload

Posted By: dave571

correct lifter preload - 02/18/10 04:29 AM

OK

trying to rememebr this, but coming up dry...LOL

I'm assembling a 383 for a friend. It has been decked a fair bit to get some comp out of it.

Stock pushrods are too long.

I have used an adjustable pushrod to figure out how long I need one to be for zero preload.

How much longer do they need to be for the correct preload?

I normally go 1/2 turn on my adjustable rockers, but this motor is still stock rockers.

Thanks

Posted By: 70Cuda383

Re: correct lifter preload - 02/18/10 04:35 AM

.030-.040 seems to be the standard answer here.

Posted By: dave571

Re: correct lifter preload - 02/18/10 06:16 AM

Thanks

Posted By: MoparforLife

Re: correct lifter preload - 02/18/10 02:14 PM

If this is a relatively stock engine and is basically street driven. As long as the lifter plunger is not bottoming out in the lifter you will be fine and no noticeable difference in performance, mileage or any other detrimental effects. There is a lot of forgiveness built into a hydraulic lifter.

Posted By: dave571

Re: correct lifter preload - 02/19/10 02:43 AM

I fear they may be bottoming. It's close for sure.

For the cost of a set of pushrods, I'd rather go that way.

Posted By: 70Cuda383

Re: correct lifter preload - 02/19/10 03:22 AM

Quote:

I fear they may be bottoming. It's close for sure.

For the cost of a set of pushrods, I'd rather go that way.

close to bottoming out would be WAYYY too long then, if you're looking at custom pushrods. they should be "just barely pushing down" on the plunger inside the lifter...remember "zero lash plus 1/2-3/4 turn on the rocker"

make sure that you're checking them with valves closed on the base circle, I forget the sequence, but it's something crazy like TDC #1 compression stroke, check intake on #1 and exhaust on #7, rotate crank 90 degrees, check intake on #3 and exhaust on #4, rotate crank 90 degrees.

if you want, I can look it up in my rebuild book and post the correct sequence if you need?

Posted By: dave571

Re: correct lifter preload - 02/19/10 04:15 AM

It's the stockers that are almost bottoming, and yes they are way too long. That is why I was asking how much I wanted with the right pushrods.

These are About .120" too long by the looks of it.

I get the base circle thing/sequence , so we're good there.
I had a similar issue with my 400, that I milled down. I ended up using an off the shelf pushrod(for a differenet application) for that one. They gave me .015 preload if I remember right, and that worked, (although I was worried that it wouldn't be enough)

I've got an adjustable one, adjusted to zero. I took it in to the local parts/machine shop, so they could measure it, and get me ones that are .030" longer. It should work out.

Posted By: NotEnufGarage

Re: correct lifter preload - 02/19/10 07:30 AM

Can't this be resolved by shimming the rocker shaft out 1/2 the amount the head was milled? Or would that change the rocker geometry too much?

Posted By: The_Mean_Machine

Re: correct lifter preload - 02/19/10 11:43 AM

Quote:

if you want, I can look it up in my rebuild book and post the correct sequence if you need?

I need to determine PR-length on a 383 - 496 stroker with Indy heads in the near future and would appreciate if you could post that info...
Thanks,
Frank