lifter pre-load

[CobraV8]

I'm using a shaft mount roller rocker setup with an Edelbrock RPM hydraulic cam. The rocker arms have an adjustment screw, so lifter pre-load can be set to any desired value.

What is recommended for an engine with a redline of about 6800rpm? I recently read an article where the author recommended zero pre-load for performance applications, according to him even a certain amount of valve lash could be beneficial with hydraulic lifters on a high revving engine.

What do you recommend?

-Simon

[bobcowan]

A hydraulic lifter needs a little bit of pre-load to operate correctly. Check the comp cams web site. There's an excellent artical on rocker arm adjustment.

For a 6,800 redline, you'll need to be very carefull about parts selection. Standard "low buck" parts really won't work. Hydraulic valve trains generally start to float in the 6K range. Start by using lightweight parts, big rocker arm studs, beehive valve springs, and anti-pump up lifters. That rocker arm has to move up and down over 300 times a second.

[CobraV8]

Camshaft and lifters are Edelbrock Performer RPM, just like the cylinder heads. The heads came fully assembled with Edelbrocks springs and valves. According to Edelbrock these are "dyno matched" components, at least that's what they say on their homepage.

The pushrods are hardened Trick Flow one-piece, the rocker arms are shaft mounted aluminum roller rockers.

According to Edelbrock the Performer RPM camshaft and heads will make peak power at 6500rpm, so I assume the parts are designed to withstand these rpm levels.

I checked the CompCams homepage and contacted Edelbrock, however I ended up with the recommendation from Edelbrock what is turning the adjusting nut an additional 1/4 of a turn after all lash is taken out of the valve train.