Adding a second keyway to a crankshaft and cam help.

[GOSFAST]

The ride in my (new) signature gets the valves set tight enough (cold) to allow the unit to fire-up, usually around .002"/.004" intake and .006"/.008" exhaust. It is a 100% aluminum BBC build. Was blown a few years back now twin-turboed!

To the post above (what's in the can): "Works much better using oil than water (see the photo below), been using this method for some years now."

Thanks, Gary in N.Y.

P.S. All the settings were the same with the blower and the turbo's. Almost needed a "negative" lash setting (impossible) to be fired, at operating temps lash is on-the-money!

[MadBill]

I read an article some years back about a well-known West coast Porsche tuner who was going through a careful series of dyno lash loops on an air-cooled race motor. Power kept increasing with tighter lash. They broke for lunch and when they returned, the engine wouldn't start due to so much negative lash that there was no compression..

[blown265]

In a similar vein, a side project of mine is an air cooled single cylinder motorcycle engine- all aluminium (case, barrel, and head) The factory rocker clearance is zero cold, and when the engine is first fired the valve train noise is fine. When hot, no so good.

I went through a hot lash loop like that mentioned by Madbill, and the result was the same. Power went up each time (data logged with a Glute-o-meter) and the valve train clatter went down, but the next day it wouldnt kick start with the (now) open valves. As a compromise, I cold set the pushrod adjusters as tight as possible without lifting the valves.

I wonder if vintage race teams reset a hot lash just before the race?