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........now the topic is cylinder heads. I’m building an engine for a C1. To be used on street mostly with occasional strip trips. Short block is 400 CI sbc with hyd roller cam. 2000-6500 rpm range. Compression 10.8 to 1. Camshaft is about 230 @ .050 with 525 lift. Single plane intake. Now, given all that, I am at 5000 ft elevation in Denver. I have been told intake cfm should be anywhere from 180 to 220. That is to big a range. I’m thinking 195 or 200 or less. I’m looking at good heads like AFR or the like and have been leaning toward full CNC. Is my thought off at 195 cfm? Thanks in advance
I'd suggest a cylinder head in the 195CC range with a smaller combustion chamber. I'm an engine builder/shop owner and do a lot of muscle car/race engines in the Ohio valley. (but the dyne I use is only ~850' above sea level). At high elevations, your air is thin and less dense. You will benefit from the velocity of the smaller runner vs the slower 200CC+ ones. Higher elevations can get away with more compression before running into detonation issues. Higher elevations will require more spark advance as well. This is the reason for the smaller chamber.
Thanks guys.
I understand the port velocity thing at elevation, as having worked with oval port bbc.
Here is the head I think I have decided on.
AFR 1034 - full CNC, 195 intake - 65 cc chamber -
I once had a set of Brodix 195cc intake port heads on a 350SBC. Crane .467/.494 lift, 222° duration I, 234° duration exhaust, on a 112° LSA. Ran good, great street manners, but I wished I would've gotten the next size up, say 210cc intake ports. Anyway, this was at 600ft elevation. A 400/406 small block Chevy would really be choked with a 195cc intake port, at least at 600ft elevation. Can't speak about high elevation. Never tuned there. BUT, my 350 was also running a 350 turbo trans. If this was my choice, and was gonna run at 600ft elevation, with a 4spd trans, or more, I'd be looking at 225cc intake ports, minimum.........
Last edited by grinder11; Apr 23, 2021 at 03:14 PM.
Those heads will serve you well. I would however suggest completely disassembling the valves/springs to ensure cleanliness, concentricity, spring pressures, run-out, etc. Even if you don't have the means to measure pressures, run-out, or such; you will be able to catch any major errors like nicked/rusty springs, missing seals, tc. Now is the time to eliminate any of these possibilities.
Ditto on that one...Good choice though overall those are real good performers.
They have good airspeed which you want on the street. If youre in Colorado Vortecpro can take a look at them for you he is expert on cyl heads.
Question for engine builders........
