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Need help on a 400 sbc

2K views 12 replies 7 participants last post by  chevy lover 
#1 · (Edited)
Just got a 72 impala conv starting talikng the engine apart for a performance rebuild then out of curiosty i took down the casting number to find out what im working to find out that its a 4 bolt main should i scrao it or should i try to find something thatll work with it
? thanks
 
#8 ·
420hp is pretty easy in a 400. 400's love air and 200cc heads are perfect for street 400's. Give it around a 280 duration cam, good hi-rise dual plane intake, 750 carb and 1 5/8" headers and you are there. Keep compression to about 9.5:1 to run unleaded fuel. To get more hp, the 5.565" connecting rods become the weak point as the main cap area is the weakest part of the 400 but going to 350 5.7" rod gains strength but also gets the connecting rod dangerously close to the camshaft.
 
#12 ·
What are you wanting to keep stock? The stock crank should be able to handle the power you're looking for. You might need to have the engine bored so you'd need new pistons. You're going to have to put a decent sized cam in it and it'd really help with a set of good aftermarket heads as Tornado Tech mentioned. If cost is a main issue for wanting to keep stock parts then you should sit down and figure what it is going to cost to recondition the rods and the cylinder heads to be suitable for a 400+hp application then compare that to what it would cost to buy a set good set of aftermarket heads and rods. I'd bet you'll be surprised.
 
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