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Old 05-26-2012, 02:08:51 AM   #1
Kermit Compeau
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400 small block horsepower limit

I've got a 400 SBC with what looks like a stock bottom end. I'm looking to pep it up a little bit. Right now its got what sounds like a mild cam, Weiand manifold, shorty headers and a 750 Holley on it. Bought it used so exact specs are unknown.
What ever, its too mild. I'm thinking of stuffing a few turbos on it, maybe some better heads, and so on. Any ideas on what sort of abuse the short block might take? I'd like to coax 600 hp or so out of it, but I'd hate to grenade it right away.
I figure 600 hp will be fast enough to make things interesting, but maybe not explosive. Any suggestions for other mods or guesstimates on what the short block might take would be appreciated--Thanks!
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Old 05-26-2012, 02:53:35 AM   #2
hhott71
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If you can afford to mess with turbos, you can afford to buy the right parts first.
Go with a DART block
Forged crank and H-beam car screw rods
D-shaped Forged Pistons.
Roller valvetrain
AFR large chamber heads
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Old 05-26-2012, 04:28:35 AM   #3
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^^ At that HP level,.... what he said ^^
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Old 05-26-2012, 04:39:44 AM   #4
red78z
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you do realize that you wouldnt really notice the difference between 400 and 600 horses unless youre on a track. Just cruising and driving around town isnt going to give you the time to tell the difference .
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Old 05-26-2012, 07:46:38 AM   #5
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Quote:
Originally Posted by Kermit Compeau
I've got a 400 SBC with what looks like a stock bottom end. I'm looking to pep it up a little bit. Right now its got what sounds like a mild cam, Weiand manifold, shorty headers and a 750 Holley on it. Bought it used so exact specs are unknown.
What ever, its too mild. I'm thinking of stuffing a few turbos on it, maybe some better heads, and so on. Any ideas on what sort of abuse the short block might take? I'd like to coax 600 hp or so out of it, but I'd hate to grenade it right away.
I figure 600 hp will be fast enough to make things interesting, but maybe not explosive. Any suggestions for other mods or guesstimates on what the short block might take would be appreciated--Thanks!

OEM 400 blocks are a crap shoot at 600 and even at 450 horse.

I would go with the Dart SHP or the SHP Pro block both are good choices over any 400 block.

Here is a link to look over.
http://www.stevesnovasite.com/forums...d.php?t=185248
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Old 05-26-2012, 08:03:14 AM   #6
5spd540
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Cant go wrong with a dart block
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Old 05-26-2012, 10:08:49 AM   #7
71camaroz27
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How fast do you want to go?
My stock bottom end 400 (yes short rods) went 11.70 on the motor, and 10.40 on 2 stages of nitrous.
Dart II sportsman II cast iron heads and a Vic Jr. in my 80 street/strip Malibu.
Thinking back, I did stud the mains, but it was a cast GM crank, and SPS (ya old school) rod bolts.

It was alway in the back of my mind... "One day i'm going to scatter this thing", but it ran strong for 3 years.
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Old 05-26-2012, 10:18:52 AM   #8
Rich Schmidt
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I have run stock 400 blocks,cranks and rods making some serious power,like a little over 500 on motor plus a 200 shot. All without fail for hundreds of runs. The down side to 400's is head gasket sealing. With turbos,that will be your downfall. I am talking those power levels with freshly machined/deck blocks and new iron Dart heads,not junky yard stuff.

So aside from the engine needing to be fresh,or at least in very good condtion,the head gasket seal is going to be the dealbreaker for your turbo setup. You should be able to get a 50% power increase with 8 psi of boost,and thats really pushing it on stock 400 decks and gaskets.
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Old 05-26-2012, 10:55:49 AM   #9
warped
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You can get a reliable 500+ hp a lot easier and cheaper if you go with a big block. Depends on what you want to do, but putting together a twin turbo setup will be $$$! Good luck.
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Old 05-26-2012, 03:16:49 PM   #10
strstk71
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at the very least O-ring the block to improve the head gasket sealing like you would for nitrous.
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Old 05-26-2012, 06:55:50 PM   #11
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My friend's 406 blew up after about 3 years of 95% track only use, with a tear down and refreshing every winter in between. It had, I think, a GM block and crank, everything else was aftermarket (rods, pistons, top end, etc). It was an 11:1 NA motor running mid 11's in an '86 TA. It wasn't even a really high revving motor, he shifted it at around 5500 rpm.

Cliff notes - my friend's 406 blew up at around 500-550hp NA.
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Old 05-26-2012, 08:25:42 PM   #12
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If I remember right core shift was one of the things to look at with factory 400s look around the cam tunnel make sure its about the same thickness on each side.I beat one for 8 years mid 11s alomst 120mph and even used for a work truck motor i would get on i 95 and turn 4500rpms from fort pierce to Jupiter 3 time a week stock crank too hit 8000+rpms one time doing a burnout cuz the rev limiter chip fell out lol
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Old 05-26-2012, 08:39:56 PM   #13
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Talk to this guy

http://www.nastyz28.com/forum/showthread.php?t=241820
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Old 05-27-2012, 01:37:21 AM   #14
Kermit Compeau
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Thanks for the info. What I'd like to do is get into the 10's. It may not be possible to do with the stock bottom end, but I may piece together a turbo setup, just looking for 8 lbs boost or so. If the 400 grenades, oh well and then I'll probably go LS1 since the stocks blocks seem to be up to heavy abuse.
My problem is that I compare my car's acceleration to my Kawasaki ZX100's acceleration and it just seems gutless, so the car's going to have to catch up to the bike in terms of power to weight ratio. At least that's something to shoot for. If I can get the car's weight to 3,000 lbs. and the power to 600 hp, I think that'll be satisfactory. Thanks again for the info. This web site is tremendously helpful.
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Old 05-27-2012, 03:49:00 AM   #15
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I wouldn't build a 400 small block to run in the 10s if you want any kind of longevity at all. It just won't handle it in an average weight Camaro. You can build one to run 10s, sure, but it won't live very long. Use an aftermarket 400 block or just go BBC/LSx now and skip the 400 completely. You'll be money and time ahead.
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