420 cid 400 block Limitations

What are the power Limitations of a 400 block?
I was looking into twin turbo or single turbo charging the block but i was told that it wouldn't be able to handle that kind of power.
And that 600 to 700 horsepower would be pushing it to the edge.
I was suggested to get a bow tie block instead.

Well.. 400's are beasts. Lots of power/torque to be made with them. BUT.. i have heard that 400's overheat easy, due to lack of cylander wall. But I am not 100% on that.

I'd say you should invest in an aftermarket 400 block if you want that much power. You could build up the factory block to take that much abuse but by the time you're done you still have a weak factory block and it would be better to just buy an aftermarket block that will have better castings.

Stephen is right. The machining adds up fast. You'll need a re-bore, line-bore, gun-drill, freeze plug tap, oil gally tap, deck, deck steam hole drill, oil pan rail rod clearancing, camshaft galley rod clearancing, ya da ya da ya da. You'll have $1000 to $1800 in machining into the old engine block.

Better bet is a World Product's Motown block, already machined & ready for your cleaning & assembly. Just order it with the bore you want, and you get beefier block, nice, heavy duty 1/2 inch studs in the 4-bolt mains, and on-the-mark CNC machining throughout.

Could you post the links of that motown block? and what about fuel injection? if you want to keep the retro-cooling??

There are quite a few stock blocks handling over 800rwhp.

Could you post the links of that motown block? and what about fuel injection? if you want to keep the retro-cooling??

There are quite a few stock blocks handling over 800rwhp.

Sure, here you go: http://www.worldcastings.com/newstuff3.shtml

Enjoy. Be sure to check out their Hardcore 454 smallblock. Fuel inject it all you like!

Price is about $2000.

These blocks will accept any Gen 1 small block parts, so if it will work on your 350, it will work on this block. You can also order it with 400 or 350 mains, your choice. The race block is machined a little more and can handle a 4" stroke crank without additional machine work. FWIW, these are very strong blocks and very high quality pieces.

Highlander, I'm not sure what you mean by "retro-cooling". These blocks use a traditional SBC style cooling setup, but the passages are larger and can circulate more coolant for better cooling.

Retro-cooling means cools the heads first then the block.

Ah, if you want LT1 style reverse flow cooling then you're SOL. It would be a cool option, and would probably support quite a bit more horsepower. Still, those blocks should handle more power than any of us will ever need. :)

Ah, if you want LT1 style reverse flow cooling then you're SOL. It would be a cool option, and would probably support quite a bit more horsepower. Still, those blocks should handle more power than any of us will ever need. :)

I dont think reverse cooling is all it's cracked up to be anymore. It was a way to enable GM to run a little more compression ratio in the new LT1 for some extra engine power by reducing hot spots on the combustion chamber. However, with the advent of superior fuel injection systems, the plethora of aftermarket aluminum cylinder heads, and ceramic coatings, you can accomplish the same thing with conventional cooling.

Therefore, I think a conventinal SBC with new technology is probably on par with the LT1 for performance potential.

The LS1, well, .... now that's a different story!

Okay. Now here is the position I'm standing in.
I already have the 420 cid small block with 4 bolt main. coler crank, scat rods, Je pistons with AFR heads. the original intention years ago when i got this was for a N/A motor.

So would you all suggest that i sell that motor and get the aftermarket block to push 700 hp through a turbo?

My friend is pushing a little over 700 hp on a 400 block with a Vortech supercharger and he sprays it for close to 900. I'm assuming he must have been shooting dice everytime he ran it.

If it's a factory 4 bolt main block I wouldn't throw too much boost at it. The factory 2 bolt blocks were stronger. If you are planning on boosting with a factory 400 block you should find a clean 2 bolt main, and have it machined for splayed outer bolts for more clamping force on the crank.

Good luck with whatever you decide to do.

- Justin

How about 10 psi at 8:5 compression?

10 PSI should be fine with that compression. Do yourself a favor and add an intercooler as well as an alky kit to help control detonation. :)

Oh yeah i'm putting an intercooler on it. I was going to go 15 psi with the intercooler but you all got me scared now! HA! I'll just go 10 psi to be safe.

My friend is pushing a little over 700 hp on a 400 block with a Vortech supercharger and he sprays it for close to 900. I'm assuming he must have been shooting dice everytime he ran it.

Is this friend of yours driving a race-only car? If it's a race-only engine, you can fill in a portion of the engine's water jacket with Hardblock, an epoxy compound that stiffens the engine block. The downside is, of course, a reduction in cooling capacity. The upside is that in a drage race environment, there's always plenty of time after the race for the engine to shed all that heat it made in the ten seconds or so of hard driving.

If you are going to relegate the car to a trailer only, you could harden your engine to make it support some additional horsepower.

i say that about 650-700 hp is where you start cracking 400's... seen it a few times... i know thats not very many times in the big scheme of things, but that seems to bewhere your throwing the dice...

I have seen the 400 blocks crack in the cylinder walls anywhere from 650-750 hp in a normal block. I have not seen a hardblocked block crack but then any engine that we built that was really trying to make more than 700hp we automatically went for the aftermarket block for the thicker walls and beefier main webbing. If you plan to run your block harder then I would rock it up to the bottom of the freeze plugs. The heat is concentrated in the top inch of the cylinder and we have actually seen COOLER oil temps from separating the water from the oil with this thick layer of hardblock.

Stephen is right. The machining adds up fast. You'll need a re-bore, line-bore, gun-drill, freeze plug tap, oil gally tap, deck, deck steam hole drill, oil pan rail rod clearancing, camshaft galley rod clearancing, ya da ya da ya da. You'll have $1000 to $1800 in machining into the old engine block.

Better bet is a World Product's Motown block, already machined & ready for your cleaning & assembly. Just order it with the bore you want, and you get beefier block, nice, heavy duty 1/2 inch studs in the 4-bolt mains, and on-the-mark CNC machining throughout.

since when do you have to gun drill the block? steam hole drill? the aftermarket block still need some machining. $1000 in machine work for the whole shortblock maybe.....probably not if an aftermarket crank and rods were used. but thats not the block. now way he'd have a grand into block machine work. im not saying the stock block is better, but i am suggesting if the power level isnt going much about 600rwhp a stock block will work.

:bow: motown blocks