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Old 07-19-2004, 03:17 PM
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400 Compression, Stock Pistons

Any guesses to what compression the following will make?

400 block, standard (4.125) bore,
Stock redone crank (rod bearings .010 over),
stock rods & stock dished pistons,
#461 heads (not modified, 64cc I believe),
Comp #280 hydraulic (230/230, 480/480) ....

We run circle-track (dirt). We were trying to nurse a 355 through the end of the year but it can't go three laps without getting up to 230 degrees -- with a good fan & shroud & aluminum radiator, etc., etc., etc. I think one of the heads is shot, if not worse -- it was a used motor that came for the right price (that price being zero). [The guy that gave it to us has been beathing his head against the wall trying to help, and it'd be a solid motor if not for the heat deal ...]

We've already tore up a head-gasket, replaced gaskets & flopped heads (late 80s van heads, I don't recall the casting #, that's how impressive they were). Seems like the exhaust pressure out of the pipe is not as strong on the left as it is the right. We thought it might just be an anomaly of the firing order or something but then realized that the bad headgasket was on the right, and the corresponding head is now on the left (where the exhaust seems weaker).

Looking to make some good low-end; our only restriction is a minimum of 12# vacuum -- I don't think the cam & combo will have any problem seeing that. The 355 with an Edelbrock 2102 cam (204/214, 420/442) is pulling about 20#.

Thanks, first post.

Deak-Jr

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Last edited by Deak-Jr; 07-19-2004 at 03:28 PM.
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Old 07-19-2004, 03:19 PM
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tough to say without exhaust, intake or carb figures. Your heads are the bottleneck, probably abou 350-375 horse-

K
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Old 07-19-2004, 03:27 PM
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Stock Q-jet rebuilt,
GM late 80s truck manifolds,
GM spreadbore intake -- believe it was a marine intake.
(I don't have casting #s for those handy)

We can't run headers; must run stock castiron intake (or one that appears to be -- we're legit, though).
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Old 07-19-2004, 03:28 PM
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From my references, the 400s came with 8.5:1 compression, except the 1970 which had 9:1. All of the factory engines I've seen came with 76cc heads. So, if you put 64cc heads on a stock engine a rough estimate of your compression would be about 9.5:1 or maybe a little more.
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