Visit The Dirt Forum for More Information

Author Topic:   Cam Low Down
DirtDobber
Dirt Forum Racer

Total posts: 79
posted May 10, 2002 02:01 PM
What are the steps used for adjusting SBC hyd. lifters? Cold at 3/4 turn or running with some clearance?
I quess I am getting confused with all the settings I am reading about.
We have just set up a pure stoke engine with a rather warm cam. I used the cold method and the car performed well but I would like to get a better understanding of how the adjustments made - loosing or tightening - effect power.

Monster
Dirt Maniac

Total posts: 135
posted May 10, 2002 05:45 PM
Here is the way we used to do it: Like you did, then, with the engine warm and running, back off of each adjusting nut(one at a time) until it clatters, then snug it up to just get rid of the clatter. This will put it at zero lash, or just a tiny amount of preload. What happens with a lot of preload is that as rpm increases and the valve train approaches float, the lifters take up the tiny separations that occur between parts. This action builds up and eventually holds the valves off of their seats, and power goes in the tank. If the lash is zero, the lifters cannot do this, and you can run the valve train right into complete separation, just like with a solid cam (theoretically). This is a whole lot easier to do on an engine with mufflers, which we had. And these days, I'm not so sure it's necessary, but it did make us feel bad fast at the time.

DirtDobber
Dirt Forum Racer

Total posts: 79
posted May 14, 2002 12:42 PM
Thanks!!
Could you define Tiny amount of preload?
Obviously by what you just described we would want minimal but is 1/4 round too much? How about just taking the clatter out?

Monster
Dirt Maniac

Total posts: 135
posted May 14, 2002 04:42 PM
Certainly it was no more than 1/4 turn, probably less. It was more of a feel and sound thing. If I did the math right, 1/4 turn on a 3/8-24 stud, with a 1.5 rocker, will equal .017 or so rocker movement at the pushrod end. When I set up 5 liter Mustangs with shimmed rockers, I shoot for .015 preload. Try 1/8 turn after clatter leaves. If you take that last portion of a turn, and you can feel the engine labor, it's too much.

WesternAuto17
Dirt Freak

Total posts: 248
posted May 15, 2002 10:13 AM
What about solid? I'm havin a heck of a time gettin them to settle down.

With engine cold, I run the nut down to .020, and than tighten the inside ***** . Than I put the stud girdle on. After the engine runs for a few minutes, I take the covers off and I have a couple loose and a couple too tight. The cam card says .016 hot.

Am I just retarded or what?

6pack
Dirt Maniac

Total posts: 128
posted May 16, 2002 01:32 AM
Put your stud girdle on before you adjust, and tighten it. Only loosen the cylinder you are adjusting.

Back to the Archives