70 Z28 LT-1 Cam questions

[Kurt S]

John's procedure now lives here where it's accessible:
http://www.camaros.org/302valves.shtml

[Hotrodpaul]

Awesome info. Thanks Kurt!

What would be the proper cold setting for a L-89 big block with the factory aluminum heads? It has the stock GM L-78 solid lift cam which I believe is set at .024" Int and .028" Ex. I would presume the Aluminum heads would expand at a greater rate than the iron and open up the valve lash when hot.

Paul

[Chevy454]

Paul: my service manual calls for 22/24 *hot*, so I'd try 20/22 *cold*, get it warm, and then check it...a little tight is better than a little loose. Just remember....set the intake as the exhaust opens, set the exhaust as intake closes...

[Kurt S]

I believe this post-script is being added to the article:

Note:

This progressive technique will ensure that ANY solid-lifter cam has the lifter for the valve to be adjusted on the base circle of the cam, but the actual lash dimension will vary depending on the height and length of the clearance ramps and the TRUE ratio of the rocker arms. The only way to determine that is to set up two dial indicators (one on the pushrod end of the rocker and the other on the valve spring retainer) and take readings on both in one-degree (crankshaft) increments for 720* of crank rotation, to develop a crank angle/cam lift diagram.

The measurements have been done for the "30-30" cam with stock stamped rockers, but for any other cam and rockers, the same thing must be done; we know from our work to date that the small-block stock stamped rocker ratio is 1.37:1 at initial contact and peaks at 1.44:1 at full lift (vs. a spec of 1.5:1), but we haven't measured a big-block. The BB nominal ratio is 1.7:1, but we don't know what it REALLY is either at initial contact or at full lift.

[70CitrusZ]

This procedure is the same as what is recommended in my GM service manual, with the exception of the 1.37 vs 1.50 factor on the lash.