[tubman]

This may sound completely O/T, but hear me out. I have a '54 Chrysler Hemi in my vintage dirt car. When I needed to rebuild it, i decided to do it right; I ended up with new forged pistons, prepped heads, and an Engle roller tappet cam for starters. The cam was new, but came with no instructions or even a cam card. I called Engle and had a long conversation with one of their techs (who seemed to know what he was talking about). He told me that anything between .010" and .030" would work fine. The difference is how you want the cam to work. Tightening up the lash increases duration, and backing it off decreases it. For racing at least, he said this was one of the final factors in tuning an engine. He sounded credible and all, but not wanting to take any chances, I asked him if he could get me the original manufacturer recommendation. He finally came back to me with .014" on the intakes and .018 on the exhausts. That's what I set them at, and the engine runs fine. I was vintage racing and didn't need that "last little bit". Since mine was a roller cam, maybe this doesn't apply to flat tappets, but he said it did. Just another factor to ponder.