Thread: Hydraulic Lifter Pre-Load

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Been away from the 'gearhead' stuff awhile and the memory cells are a bit depleted.

I'm re-assembling the upper-end of a SB Chevy that's w/ a hydraulic cam.
What's the proper pre-load for the rocker / lifter nuts?
With each lifter on a cam lobe base, after the push rod was slightly snug - I went an additional half-turn w/ the rachet.
Am I remembering this correctly for the initial set before I can adjust it while running?

at o lash given them 1/2 turn .

One half turn is safe. Some say a quarter turn others more. IMO as long as the rockers aren't clacking, looser is better.

1/4 is not much and a full turn is to much for me i have been setting them for over 20 years at a1/2 turn

I use a 1/4 turn but as stated I know some who put 1 full turn, a half turn is a safe bet.

my engine didn't start right away so the lifters were already pumped up. I adjusted until all vertical movement was out of the rods and left them at that

My Chilton says a full 360 deg turn, however I think that is way too much.

GM calls for 3/4 turn. However, used lifters (and sometimes new) sometimes will not take that much and will start missing. 1/2 turn is sufficient. Firebird knows this as we went round an round on his for the longest time.
Ed

nice pick denny i like them 0.30 thats 1/2 turn and no more. i do this when lifter is at the base of the cam this is done when one is at just full lift when intake is off and never had to go back to them .if so somthing is goning south i like to see more spring pressure this help to but if worried go solid cam

by the way i have seen snap rings from the lifter in the valley from 1/4 or less it hammers the snap rings out real nice

yes that what i said didtn i do them when one is up on full lift one is at the heel of the cam ajust the one on the heel dose not matter intake or ex as long it the same hole if the intake is off why not do the lifters? maybe i didtn spell it out rigth but i have set lifter a long time on soilds hyd and roller to and they are set rigth

ok i know i not to clear some times

i am working on it .i guess i can do it better than spelling it out

Originally Posted by DennyW

Guys, listen. The adjustments for these is all over the place. 1/2 turn is fine, how ever. The whole point of the adjustment is to put the lifter plunger in the center of the total travel, and not have the plunger come up and hit the plunger retainer. So, if you adjust them to light, you could pop the retainer out, and the plunger come up out of there, and possibly push a valve into your piston. To tight, and you put excessive load on the cam lobs. It is a hydraulic cushion, thats all. The basic adjustment is 3/4-1 turn. If the lifters won't adjust properly, change them.

PS: If you run high oil pressure, or a high volume oil pump, it's always a good idea to install Anti-Pumpup Lifters. Why ? At higher oil pressure, at high rpm's, it will actually over pump the lifter because of the bleed down rate of the lifter. This in turn, will pump up the lifter opening the valve more than normal. Also known as valve float.
Just trying to help.

After doing a piston ring installation, one exhaust valve on my pushrod hydraulic tappet 2 cylinder Polaris RZR 800 engine is not closing, as evidenced by a rough idle,carbon on the valve seat, and a cylinder compression of only 80 lbs (the other cylinder is 110 lbs).I've disassembled the top again and installed new rings on both cylinders. I've disassembled all four lifters and cleaned them, put in new oil in the plungers. Now, when I tighten down the rocker arm bolts to the recommended 22 ft/lbs, all the valves push open about an 1/8th inch. There is no adjustment on these rocker arm holders, just one center bolt tightened to 22 ft/lbs. Will these tappets pump down and allow the valves to close when I start the engine? Might a piston hit a valve and do damage? Should I remove the lifters and remove the oil and let them pump up on their own? Ah man! I surely liked the solid lifters and adjustment bolts on my chev 348.

Welcome to the forum. IMO there's not much similarity to an automobile lifter and your Polaris. I'd probably look at the cost of four new lifters vs trusting the old ones, but that may be totally bogus as I really know nothing about them. All of the instructions say to simply torque the retaining bolt to 22ft lbs, + 2 so it doesn't seem to be too critical - anything from 20 to 24 ft lbs is good per the book. What's your Polaris shop say? I'd torque them to 22 and fire it, but again I know nothing about small engine details so I might swing by the local small engine shop to talk to an expert in my area first.
Just a thought, but do you maybe have a damaged exhaust valve or valve seat causing the leak? Maybe lap the valves to ensure good sealing?