Hydraulic lifters

I am confused as to the logic of hydraulic lifters adjustment.

On a pre-1968 engine with an adjustable valve train my book says to take up all the slack and then give the adjusting nut another 3/4 of a turn. If this is done with the lifter cold and empty of oil then what is the point of the pump-up design of the lifter? It has no lash to take up. Perhaps someone could explain.

Secondary question. If hydraulic lifters are not so good at higher revs and have a limit of maybe 6,000 then why do Edelbrock use them on their Performer RPM package?

By taking up the lash, means to take up the push rod free play with out depressing the plunger in the lifter. 3/4 to 1 turn should center the plunger where it should be. There are lifters made for performance use (Anti-pumpup).

VIC

CAV40
Lemans Blue
Owner built 302
Stack Inj.
Getrag trans

Most hyd lifters have a light spring holding up the plunger that you would be depressing with this adjustment. Hyd lifters are good to about 6000-6500 RPM and require very little or no maintenance. Look at how many 5.0 owners get tons of miles on there cars with hyd roller lifters without problems. Mech roller lifters require periodic checking, valve lash adjustment and roller rebuilds. Solid lifters require periodic lifter adjustment.

Dave, I also have an early '68 302 with adjustable valve train. We adjusted the valve train with the engine running. I took a junk valve cover to a muffler shop and had them torch a wide slot across the top (cost $5). We ran the engine to fully warm and then replaced one of the valve covers with the cut one. We ran the engine and loosened each rocker nut until you hear the clacking sound. The nut was then tightened to stop the noise and further tightened about a half turn. The cut valve cover caught the oil and you can adjust a side in about 5 minutes. We then did the same on the other side.

Dave,
Don't make the mistake of interpreting "taking up all the slack" as bottoming the plunger in the lifter. The "slack" is in referrence to any gap between the pushrod and the plunger in its most upright position. Bottoming out the plunger will destroy your valve train. I witnessed a Corvette owner removing mangled pushrods from his engine after making that mistake.

Mark,

Over the years I have adjusted hydraulic valves and ALWAYS ended with an oil mess (rags just didn't do the trick) and NOW you share this idea about the cut valve cover. Where were you years ago? What a neat idea!

Have fun!

John

I have been told numerous times by my fellow club members that I should be changing to solid lifters but I haven't yet. For the last ten or so years I have run Rhodes lifters, the tappets that tick! Had them set when I first got the engine and then again when it was rebuilt in 1997. No interim adjustments made.

According to the sales brochures, Rhodes lifters are good for super high RPM as they pump up. I have over revved the engine occaisionally and been close to 7000 but the valves bounced before I could determine what was happening with lifters pumping up or not. Actually I was most likely trying to find a gear or hoping that the second gear corner was closer than I thought it was as I should have changed up a gear instead of holding it down in 2nd.

Anyway on this latest rebuild with cutting a long story short, I have roller hydraulic lifters on a comp cams hydraulic roller cam. It is the first time on any V8 that I have owned where I have not had Rhodes lifters. I wonder if I will spot a difference.

Malcolm

Thanks everyone.

I think I understand a bit more. The hydraulic lifter has an in-built spring which extends it even when there is no oil in it, so when the oil is pumped in it 'hardens' it at this level - meaning you have 3/4 turn's worth of wear before it will rattle.

Following the manual means the lifter spring is compressed by 3/4 turn or .020 to 0.60 thou. I'll have to check the thread on the rocker post as this will allow me to calculate the pre-load once the slack/lash is taken up.

and the idea of cutting an rocker cover for access is great.

The actual correct way set valve lash on a adj. valvetrain 302 is to set the lifter preload (which is what you are doing with that extra 1/2-3/4 of a turn) the measurement is between .020-.060, which to say is after you've obtained .000 lash. The book says 3/4 of a turn, but to really achieve acuracy (especially with non adj. rockers) you should use a dail guage to set preload.