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Old 02-13-2005, 11:20 AM
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chevy 400 block???

what is a good 400 block???
Block number is 3951509 this motor was taken out of a 71 Chevy Impala. but when i look up # it was 75 to 78???

Block number is 3951511 this motor was taken out of a 72 Chevy pick-up i think.

i want to make a 600 to 700 hp on spray

Thanks for your help

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Old 02-13-2005, 11:48 AM
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I have the 3951511 block. It has held up well. It is a 4 bolt main. I studded the mains on it to try and make it stronger.

The 2 bolt main blocks are actually stronger. I don't know what the first block you mentioned is, but if it is a 2 bolt use it.

Also, check to see which if either is standard bore. Mine was, so I bored it .020" over. That way I might get a couple more rebuilds out of it.

Have the block you choose checked for cracks. That is important with 400 castings.

I used Fel-Pro head gasket #1014. It has a revised cooling passage that you will need to drill in your deck surface. It keeps the two center exhaust valves cooler. You just get a 5/16" drill bit. It was easy. It tells you how to do it in the instructions. That mod is well worth it.

Have your deck milled down to a zero deck. 400 kits will end up with higher compression. You will want your quench to be tight.

Here is a kit I used to bhttp://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&category=33623&item=7911861 867&rd=1uild my 400.
The rods are very light in this kit. It worked well. I used 64cc Sportsman II heads to come up with 11:1 compression. I drive it to work everyday.
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Old 02-13-2005, 12:08 PM
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6-700 horse warrants an aftermarket block, or some serious mods to a stock block like studded mains, grouting and splayed caps.

K
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Old 02-13-2005, 01:57 PM
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700HP from a 400 block is possible but the stock crank and rods wont handle that much.
dont bore the block any more than absolutely nessessary,to keep the cylinder walls as thick as possible.
magnaflux to ensure it has no stress cracks to start with.
heat treating the block to reduce casting stresses would be a good idea before any machine work.
deburr and fillet all main webing to remove stress risers.
use main studs and if money allows after market caps.
if its for street use I wouldn't recommend using block filler cause 400's run hot enough and the short rod to stroke ratio puts more side load on the pistons and increases scuffing against cylinder walls.
install a quality steel crank,rods,forged pistons,large port heads and hose the NOS to it.
happy racing
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Old 02-13-2005, 02:31 PM
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I have no troubles with my 400 running hot. I don't know where that myth comes from.

I wouldn't use aftermarket caps on a 4 bolt main. You are much better off just studding them. I think splaying a 4 bolt 400 actually makes it weaker.

A 2 bolt is worth splaying if you are going to build it over 600 hp.
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Old 02-13-2005, 09:05 PM
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both 400's are bad.

so do i build my 350 block now??? but what stroke 3.750 or 3.875 it will have 4340 eagle crank rods je's 11.5 to1 c/r

dart pro1's cnc ported
bowtie intake to mach
cam will be roller with .680 lift 270 to 280ish@.050 and 112sep.

my engin now is 307inch in a 69 chevelle
with the pro1's
cam is dz302
bowtie intake
650 demon
points distributor/msd box

it made 330rwhp N/A on spray was 520rwhp and 612ft @ wheels

what do you think of the 383/395 inch or if i can fined a 400 and build a 421/434 incher
Thanks Ryan
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Old 02-13-2005, 10:11 PM
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Hold the phone.....Did you say 612lbft to the wheels from a 307? I guess if you really have all those parts on it, it is possible. You must have the highest HP 307 ever built.......
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Old 02-13-2005, 10:28 PM
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A 650 CFM carb feeding that engine?
Making 520 rear wheel horsepower?

A cam and heads that big idling okay with a 650?

Sounds a little fishy?

How did you find out both 400 blocks were bad?
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Old 02-14-2005, 01:05 PM
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a dz302 cam is not that big it is....
346@.020 254@.050 .485 lift and 114sep.
650cfm is just rite for a 307inch that spins 6500rpms

520rwhp is on spray and 330rwhp is N/A.

both 400's spit a rod

what do you guys think of 383/395 sbc and which one.

are the pro1's to small for a 412/434sbc.

Thanks
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