drjimmy

Hello All,

I have a set of hydraulic non roller lifters in my 86. I am using aftermarket roller rockers. I rebuilt the engine and set the valve lash by tightening the rocker while rotating the push rod until I felt resistance. Then I gave the adjustment nut 1/2 turn to set the pre-load. The odd thing is that when I did a leakdown test, all the valves leaked. I loosened the valves back 1/2 turn and the leak stopped.

I am stumped on how to proceed. I used the valve lash method for years and have not had any issues. But it seems weird the valves leak if they are set properly. Any ideas?

Joe C

for the adjusting sequence, follow the FSM --

with the engine in the #1 TDC (compression), adjust the following:

exhaust -- 1, 3, 4, 8
intake -- 1, 2, 5, 7

(this is my personal method) instead of "rotate the push rod while turning the adjusting nut," I use a .0015" feeler gauge, between the rocker arm and valve stem, slowly tighten the adjusting nut until the feeler gauge "grabs." at that point, you should be within .001" of zero lash. then adjust the nut 3/4 turn. this method seems a little more exact or precise than the "rotate the push rod" method, which IMO is a little too subjective. this should result in a more even adjustment across the board. either method will, however, work just fine.

now, rotate the crank 1 revolution or 360° and adjust the following:

exhaust -- 2, 5, 6, 7
intake -- 3, 4, 6, 8

i've been doing .0015" thing for over 10 years now without issues. basically, you set it and forget it.

gerardvg

Don't forget to prime the new lifters before fitting them , it doesn't take much to over adjust them. takes a bit of practice then you can never go wrong again.

Krusty84

I had a motor years ago give me fits with initial valve adjustments so I just started adjusting them with the free spinning to resistance method and then firing up the engine and adjusting them the rest of the way while she idled. Never had any problems after than except for a little oil clean up.

84 4+3

I move the rocker until I can't feel it tap while tightening (basically just seating the pushrod against the lifter) then give her 3/4 turn. I did the adjustment while running a few months ago after that method and it was exactly half a turn until I just started hearing a light rocker tap while loosening.

cardo0

It reads like your idea of "zero resistance" is not the same as "zero lash". But first of all the lifter must be on the "base circle" of the cam. You didn't mention base circle but I find it by watching which valves open in the firing order. Easiest way I can explain is if you watch which plug wire the distributor rotor is pointing to that would the cylinder under compression stroke and ready to fire which means both valves have to be closed and on the base circle.

Now for zero lash that is when you can roll the p-rod with your fingers but not move it up or down. Your really not looking for resistance but you want to identify when the p-rod is not going to move the valve or depress the lifter plunger yet has no slack between rocker arm and lifter cup.

Hope this helps.

BTW I use 1 full turn of preload.

VikingTrad3r

drjimmy

All good advice on how to adjust the rocker arm but that is not the question I was asking. Why do the valves leak if they are set correctly? Has anybody ever done a leak down test on their engine after adjusting the rocker arms?

Joe C

sorry - assumed the valves were too tight since when you loosened the adjustment, the leaking stopped - . unless you have some sort of a valve face/valve seat issue, you shouldn't have leaking with the valves seated and correct adjustment.

cardo0

Not sure where you are going with this? Now you could do a leakdown test with the rocker arms off once you get the cylinder to TDC. But normally you test for leakdown with the lifters adjusted whether recently or long ago.

What it appears to me is if you had to adjust the litter preload to stop valve leakby on a leakdown test the lfters were not adjusted correctly. It implies the valves were held open by overtightning/overadjusting the lifter/preload.

Hot Rod Roy

If the valves leak with correct adjustment of the valves, you have a valve or seat problem, or a valve spring problem.

drjimmy

Have not eaten crow in a while but have to now. My mistake was adding too much preload as stated.

I was adjusting the rocker arms to the point the where the pushrod would not rotate. Did it again until I just felt resistance and then added half a turn. Checked for leaks. All good.

Thanks for the assistance.