how to determine pushrod length, 351W, nonadjustable valves, rollercam, hydraulic lifters - Ford Forums - Mustang Forum, Ford Trucks, Ford Focus and Ford Cars
 
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post #1 of 3 (permalink) Old 12-07-17, 10:52 PM Thread Starter
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how to determine pushrod length, 351W, nonadjustable valves, rollercam, hydraulic lifters

Okay, nukkleheads, here's an often repeated question. There is a lot of wrong information out there, so let's see if we can get it right in one go so future readers get the right information.

Setup: 1996 351W 5.8L. Stock everything, rollercam, roller hydraulic lifters, stock rockers (non roller).
Trying to find: pushrod length.
Own: pushrod length measure device.
why am I dinking with it: valve train noisy

Details: I've read that for non-adjustable rockers, the only two ways you can adjust - well - anything - is by changing pushrod length, the lifter's height, and shimming or shaving the rocker pedestals. I have no intention of doing anything to the pedestals, or the lifter heights, so that leaves the pushrods. The valve train as it stands is NOISY, and I've determined I have oil coming to the lifters, and they're pumped up. That only leaves the pushrod lengths as culprits.

I've seen a lot of videos out there describing "preload", "lash", etc, but most of these videos have to do with adjustable rockers. I don't know what the right procedure is to determine the pushrod length for a non-adjustable rocker. I am thinking it's RELATED to how it's done for adjustable rockers, but not the same. In other words, get lifter onto the base of the cam lobe, then start tightening the rocker's non-adjustable bolt until the slack goes out of the pushrod, then figure out how much further you have to tighten the bolt until it snugs up and reaches torque range. This is assuming the lifters are either all the way pumped up, or you're watching them *very* closely to make sure they're not depressed into their bores. Obviously, if there is too MUCH slack, when the bolt is all the way tight, the pushrods are too short. If they're too long, and the lifters are pumped up, the valve won't close all the way.

Currently, I can turn the bolt about 1/4 to 1/2 full turn before it reaches torque snugness.

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post #2 of 3 (permalink) Old 12-08-17, 04:28 PM
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Re: how to determine pushrod length, 351W, nonadjustable valves, rollercam, hydraulic lifters

See my other post.

Ever notice that there's so many high performance parts available for GM products?

Did you ever think that maybe they NEED them?
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post #3 of 3 (permalink) Old 12-12-17, 10:17 AM Thread Starter
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Re: how to determine pushrod length, 351W, nonadjustable valves, rollercam, hydraulic lifters

I called my local machine shop expert and asked him the same question. He said the exact same rules for adjustable vs non adjustable rockers apply. First, get the valve in question to the base of the cam lobe. Then either:

A. tighten down the rocker bolt until all play is removed from the pushrod, then look for another full turn before the bolt gets to full torque rating

B. use a pushrod measuring tool, adjust it until there is zero lash (with the rocker bolt fully tightened down), and then the pushrod length should be 0.050" longer than that.

That's it, he said, no other guesswork.

I was asking him about hydraulic tappet theory, and mentioned a few things that were bugging me. ("it's impossible to compress a pumped up lifter in a vice, it won't compress no matter how hard I try!", "even when I leave a lifter on a cam lobe, it takes all night for it to pump back down!", "won't putting 0.050" of preload on it when the cam is on the base, cause the valve to slightly stick out and never fully close?")

he said, "how cold is your engine oil?" I said, "garage temperature". He said, "and what is that?" I said, "about 40 degrees F". He said, "lifters change how they work dramatically when the oil starts to heat up to 250F. You can't judge them when they're cold. This is why hydraulic lifter engines run so poorly when they are cold, the lifters don't work right until they get warm engine oil in them. Don't try to fix a lifter issue with heavier weight oil, under any circumstances, fix the pushrod length."

I'll be darned. Never thought of oil viscosity changing how the lifter works.
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