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Old 02-27-2013, 04:43 PM
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cobalt327 cobalt327 is offline
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Personally I like that cam. It has a powerband that compliments a stick shift 400 Pontiac, especially w/freer flowing heads. Not to say your 48's won't be a good match, but if ported the cam can make more power.

This cam in a 400 should make just enough vacuum (11-13 in.) for power brakes, but if it was a problem I'd expect you'd have said so already. Do you know if it was installed at 108 degree ICL? You might try advancing it a little but that's something for the fine tuning stage.

BTW, do you know what pistons (description or part number) are in your engine? At some stage it would be good to CC the heads and measure the piston deck clearance to get the exact compression ratio. Your heads (assuming they're 400 heads and not the 350 heads, which I seem to remember had smaller chambers but you'd need to verify that) are listed as 72cc in most places, but they usually measure somewhat higher than that if they're unmilled.

In any event, running the numbers through a calculator using 72cc chamber volume, a 0.041" quench distance, a 5cc valve relieve volume and a 0.030" over bore, I get a little more than 10.5:1 CR.

Using a wider 0.061" quench (unmilled block and 0.041" head gasket thickness), it's a little more than 10.1:1.

It would take a dish of about 15cc to get you to 9.5:1, using the tighter 0.041" quench, or a 12cc dish using the wider 0.061" quench. Note- All these figures use an arbitrary gasket bore diameter of 4.2", and a flat top piston valve relief of 5cc. Adjust this as needed for the parts being used.
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