Hydraulic lifter, roller cam valve clearance/preload

[wrogers55]

My 418 small block with Comp Cam roller hydraulic lifter motor has the rocker/valve lash set at zero. No preload. The rocker will "slide" easily across the valve tip with the valve closed, but no clearance and no preload.

I suppose this is avoid the lifter from pumping up since it's already maxed out in height.

This is a 550+ hp flywheel motor at 6,250.

Any comments on this being a good, bad or medium set up for a street only motor? Other suggestions?

Thanks,

[madmaxx]

You dont know it is set at zero, it may be set anwhere from 1/4 to 3/8 turn and it will do what you are describing. The advantage to setting the lash close to zero is if you float the valves (lifter pump up) they will not hit the piston. The disadvatage is if the valve train wears you will get lash and noise. The probability of you wearing out a vavle train in a cobra is .0000001%.

If they are set as zero as you feel they are you probably get some noise. Factory cars are set with .015" preload.

If you have high rev lifters which restrict the travel of the lifter plunger I think? you set 1/4 turn if you do more you might bottom out the plunger and now you have solid lifter which in some cases could hold a valve open.

[bobcowan]

Hydraulic lifters are designed to run some pre-load. If you're not sure if you have any or not, you should probably take the time to do a proper adjustment to be sure. It's not a difficult task, and doesn't take long.

One trick though. Over the years, it has been generally accepted that you tighten the adjuster nut down until you can't spin the push rods with your fingers. But with modern materials and lubes, you can often spin the rods after they're adjusted properly, so that doesn't work any more.

To find very lash, tighten the nut down with your fingers until you can't turn it any more. That's zero lash.

Here's some complete instructions: http://www.compcams.com/Technical/In.../Files/250.pdf

[blykins]

It all depends on the lifters.

Comp has two sets of lifters, one set requires hardly any preload at all, the other requires zero lash plus a 1/2 turn.

If you're running it this way, I don't see anything wrong with it.

[CowtownCobra]

Originally Posted by bobcowan

tighten the nut down with your fingers until you can't turn it any more. That's zero lash.

Been doing that for years and many thousands of miles on several moders. Works fine.

[DAVID GAGNARD]

I took an old valve cover years ago and cut a strip out of the top about 2 inches wide, the length of the cover...
this is what I do, start the motor, get it to full operating temp and then shut it down, remove one cover and put on the "modified" cover on (this lets you do the adjustment while the engine is running and not have hot oil leaking all over everything), one at a time I loosen the adjusting nut slowly till I hear the valve "ticking", then tighten slowly till it stops and then go from 1/4 turn to 1/2 turn, repeat on all valves and then go to the other side of the motor........been doing it this way forever (almost) and have never had a problem with my valve train..........

David