Thread: which Cam

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I'm far from being the BBC guru on this forum, but I'll take a swing at it. There are aspects that I feel I must address before worrying about cam timing.

First off, unless you take precautions to prevent detonation, I think you're going to be disappointed when the motor pings on pump gas. Current thinking has the static compression ratio limited to 9.5:1 when using iron heads on pump gas. Iron heads just won't throw off enough heat from the chambers to prevent detonation like aluminum will. Of course, if you have access to quality fuel, like maybe E85, then it will not be a problem.

I'd be wonderin' how much that big 33cc dome would hinder flame propogation across the chamber and what it would do to squish as well. Speakin' of squish, did you plan to use the block at 9.800" with a steel shim gasket, such as the Mr. Gasket 1131G, or cut the decks for a composition gasket? 1.640" + 6.135" + 2.0" = 9.775" stack. Maybe your pistons are taller than that, but you did not bless us with that info, so I'm guessing.

I'd also be triple-checkin' piston to valve and piston to head clearances with clay.

On Wallace's calculator, I get 10.8:1 SCR and 0.045" squish using a shim gasket, 0.025" piston deck height and 9.800" decks.

Lunati 20110713 (old number 60213). LSA 110, intake centerline 106, intake closes 46.5 degrees ABDC. Intake closes too early for the 10.8:1 SCR, 106 ICL favors power in the lower rpm range, something you will not have with a 3000 stall converter.

Lunati 1140HR. LSA 108, intake centerline 104, intake closes at 44 degrees ABDC. Intake closes too early for the 10.8:1 SCR, 104 ICL heavily favors power in the lower rpm range.

Howards 120665-12. LSA 112, intake centerline 108, intake closes at 49.5 degrees ABDC. 3000-6500, lopey idle, broad mid-range power, 3000 stall. This would be my choice. I'd make provision on installation to retard the cam a couple of degrees after I ran it for a while and maybe saw the need for more top end. I like the offset cam sprocket bushings with a Cloyes aluminum 2-piece front cover, makes advancing or retarding a snap. This cam produces an 8.675:1 dynamic compression ratio on the KB calculator. That's maybe a little high for iron heads, but with good fuel, it should be a rocket. One last thought, I might use a little more converter with this cam, maybe a 10 inch, 3500 stall.

Whatever you do, DO NOT use a thicker composition gasket to lower static compression ratio. John Erb, chief engineer for Keith Black Pistons has stated that a builder will be better off with a slightly higher static compression ratio and a good tight squish (piston/head clearance with the gasket in place) than he will be with a slightly lower static compression ratio and a thicker gasket (wider squish).

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