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Author Topic:   400 CHEVY
pa racer
Dirt Roller

Total posts: 13
posted January 19, 2001 09:46 AM
could some one please tell me all the differences between the 350 chevy small blocks and the 400 ci. head gaskets, steam ports,etc. ? thank-you.

awkwardjeff
Dirt Freak

Total posts: 218
posted January 19, 2001 09:56 AM
Well, I don't have the typing skills to sit here long enough to go through them block by block because 350 differ from each other as do the 400 blocks.
The BIG difference between them is the 400 block has the center two bores touching each other so they are considered dry between the bores 3-5 and 4-6......no water passes between the center of those cylinders to take the heat away......the 400 has a 4.125 bore stock, the 350 has a 4.000 bore stock.
the steam holes in the 400 block are normally plugged for racing to keep them from cracking across the deck.....if you need more specific information you need to be more specific with your questions.
I hope this helps for now though......Jeff

pa racer
Dirt Roller

Total posts: 13
posted January 19, 2001 10:50 AM
quote:
Originally posted by awkwardjeff:
Well, I don't have the typing skills to sit here long enough to go through them block by block because 350 differ from each other as do the 400 blocks.
The BIG difference between them is the 400 block has the center two bores touching each other so they are considered dry between the bores 3-5 and 4-6......no water passes between the center of those cylinders to take the heat away......the 400 has a 4.125 bore stock, the 350 has a 4.000 bore stock.
the steam holes in the 400 block are normally plugged for racing to keep them from cracking across the deck.....if you need more specific information you need to be more specific with your questions.
I hope this helps for now though......Jeff

pa racer
Dirt Roller

Total posts: 13
posted January 19, 2001 11:07 AM
THANKS JEFF!!
WE HAVE A 400 BLOCK BORED OUT 30 OVER WITH
THE SIX STEAM HOLES ON EACH SIDE. WE HAVE A
SET OF WORLD PRODUCT HEADS OFF A 355 WITH OUT
THE STEAM HOLES. WHAT DO WE HAVE TO DO TO
USE THESE HEADS? PLUG THE HOLES IN THE BLOCK? IF SO HOW? OR DRILL THE HEADS OUT FOR
THE STEAM HOLES? WHICH WOULD BE BEST?

awkwardjeff
Dirt Freak

Total posts: 218
posted January 19, 2001 11:40 AM
You can just bolt the heads on with no real problems, the reason to plug the holes is to keep them from cracking the deck of the block.
This should be done before the block is decked by a machine shop........the small steam holes are filled with dowel rod....I forget the size, SORRY......the bigger water passages in the top center of the bore is tapped with a pipe thread and plugged, then drill a whole like 5/16........this works two ways........it stiffens the deck for high compression living, and also keeps the water in the block a little long to pull more heat off the bores........works like a restriction plug.........these plugs need to have a recessed head on top and use a Allen wrench...........this is so when you deck the block you don't run into problems.....
most shops sell this plugs already to go for around 8-10 dollars, you can make your own for about 2 dollars if you got a good pluming supply place around.......Jeff

PS. some people will drill the heads to match the steam holes, you can do this by useing a 400 gasket........I plug the deck to keep it from cracking with the compression we run........also if you drill the heads they are a little more likely to crack themselves

[This message has been edited by awkwardjeff (edited January 19, 2001).]

pa racer
Dirt Roller

Total posts: 13
posted January 19, 2001 12:32 PM
thanks JEFF- YOU HAVE BEEN A BIG HELP!

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