What are the pros and cons of setting your lifters at 3/4s turn over 1 1/2 turns ? The 3/4 is .060 preload and 1 1/2 is .120 almost a 1/8 inch . This is on my 3.4.
I just set mine today. The Comp lifters I used only called for half a turn (.030) while the facotry service manual calls for the 1.5 turns. I used Comp's recommendation I'm using their lifters and not GM's.
I would think that depending on what the lifter was designed to operate with, it would increase load and therefore accelerate wear on the lifter and cam. In an extreme case I suppose it may cause cam failure during break in, but I'm sure that would take more than the difference of a single turn.
I spent a lot of time researching how to set the lifter pre-load on my Formula's 2.8 when I installed the 1.6 roller-tip rockers. I think plenty of people, especially novices, totally screw up when it comes to determining zero lash.
In general w/ any hydro lifters... You only need bare minimum preload to compress the lifters so can't hammer and make noise or worse break small clip on top of lifters plus adds tolerance for Push Rods, valves, etc for engine hot vs cold.
Find FSM etc w/ correct preload data. Aftermarket setup try calling the makers of that. If that doesn't help, watch the lifters while adjusting the rockers. Very Small adjustment of the rocker can be a lot bigger at PR tips because of level action of rockers. IOW Small changes at rockers can slam the lifters at top or bottom of travel and quickly wreck the valve train.
Part of L4 valve noise is because can't set preload as engine wears valve parts. More so w/ Duke engines w/ 100,000 miles or more on them.
------------------ Dr. Ian Malcolm: Yeah, but your scientists were so preoccupied with whether or not they could, they didn't stop to think if they should. (Jurassic Park)
Whatever spec you choose... I have usually heard that you are supposed to spin the pushrods, and tighten the rocker nut until they become more difficult to spin. The trouble is that today's lubricants are so good, that it becomes impossible (at least for me) to tell when the slack is gone. Instead of doing that, rattle the pushrod back and forth. When the slack is gone, it will become readily apparent. (And it will still be easy to spin.)
I have usually heard that you are supposed to spin the pushrods, and tighten the rocker nut until they become more difficult to spin. The trouble is that today's lubricants are so good, that it becomes impossible (at least for me) to tell when the slack is gone.
Well I have the intake off. And I'm using a dial indicator with an extension. The extension goes on the piston/plunger in the lifter. Set indicator to zero and tighten to desired preload. I chose .060, 3/4 turn. My engine builder suggest .050. I might contact the seller (ARI?) and see what they say.
If done correctly adjusting hydraulic lifters can be an easy procedure. He is a fool proof method. Remove the spark plugs. Make sure all rockers are loose. Set the balancer to the timing mark. Now go to every pushrod,push up and down until no motion is felt. Tighten rocker just to the no slack point but not tighter. Then rotate engine 1/4 turn, check each push rod for no up down movement. Rotate another 1/4 turn and do the same. Continue doing this for two entire revolutions of the balancer. When you are done just go to each rocker arm and give it the recommended preload turn.
------------------ " THE BLACK PARALYZER" -87GT 3800SC Series III engine, custom ZZP /Frozen Boost Intercooler setup, 3.4" Pulley, Northstar TB, LS1 MAF, 3" Spintech/Hedman Exhaust, P-log Manifold, Autolite 104's, MSD wires, Custom CAI, 4T65eHD w. custom axles, Champion Radiator, S10 Brake Booster, HP Tuners VCM Suite. "THE COLUSSUS" 87GT - ALL OUT 3.4L Turbocharged engine, Garrett Hybrid Turbo, MSD ign., modified TH125H " ON THE LOOSE WITHOUT THE JUICE "
[This message has been edited by Dennis LaGrua (edited 06-05-2020).]
Here's some pictures of how I adjust my valves. I'm actually showing 2 methods same principal. I had to retap an althread coupling to a metric size to go in to the valve cover bolt hole. Just set the dial to zero and turn till the needle starts moving, being careful not to push down on the fulcrum (?) half round washer thing under the nut. Set to desired turns or thousanths of an inch. The compcam timing degree kit is where I got dial indicater from. I degreed the ARI cam and came out right on the money, .421/.444 llift. This is actually for my s10. I think the intake is better than the fiero intake. The throats at bored to fit a 4.3 tbi which equals 60mm, runners are bigger and a whole lot shorter. Hope this helps someone.
With hydraulic lifters, you don't need to be very precise with lifter pre-load (not like a solid lifter). There's a pretty wide margin. And as long as it falls in that margin, you're OK. But ideally, the plunger will be in the center of its range of motion. Since you have a measuring device, you can measure that. Find out how far the plunger travels until it bottoms out, and divide that distance by 2. That will be your preload. It'll put the plunger exactly in the middle.
That said, I prefer to use zero lash plus 3/4 turn. I've seen a valvetrain get loose enough to clatter (after fully broken in) when I used only 1/2 turn of preload.
