Corvette Forum : DigitalCorvettes.com Corvette Forums banner

1 - 7 of 7 Posts

·
DC Crew
Joined
·
32,974 Posts
Discussion Starter #1
For all you guys out there that have one or the other. Which would be the better option? If you have one do you wish you did something different?
Which is more expensive to build. I have the option to build either as I have a 400 block in the garage and am doing some research on my choices.
 

·
Super Moderator
Joined
·
8,488 Posts
a 406 will always have the potential to out perform a 383 for several reasons,
(1) the larger bore unshroud the valves for slightly better breathing,
(2) that larger bore alows a larger total displacement with the same stroke
(3) the larger main journal size makes a stronger crank
(4) correctly built small block engines normally produce about 1.1-1.4 hp per cubic inch of displacement, the larger bore 400 block can always produce a slight advantage in total displacement.
(5)the larger displacement allows higher airflow speeds in the ports at a given rpm, that almost always allows an engine to build torque earlier in the rpm range and be more responsive at lower rpms
(6)larger displacements tend to allow the cams LSA to be tighter for a given idle quality at low rpms but the tighter LSA also tends to allow the engine to have both more overlap for a given duration that allows better high rpm breathing,and better low rpm cylinder pressure


in fact the only real advantages a 383 has are less expensive, and more comon blocks and a VERY slight advantage in low rpm cylinder cooling due to the coolant being able to pass between the cylinders, where a 400 blocks siamese cylinder walls REQUIRE steam holes in the cylinder heads to help cooling
 

·
DC Crew
Joined
·
32,974 Posts
Discussion Starter #5

in fact the only real advantages a 383 has are less expensive, and more comon blocks and a VERY slight advantage in low rpm cylinder cooling due to the coolant being able to pass between the cylinders, where a 400 blocks siamese cylinder walls REQUIRE steam holes in the cylinder heads to help cooling [/B]



How much less expensive? I have heard about the cooling problem and a local speed shop sugested drill and taping into the water jacket with steel braided line is this what you refer to with steam holes?
 

·
Super Moderator
Joined
·
8,488 Posts
once you have a 400 block, building a 400 -406-421 even a 427 -432-454 sbc usually costs between about $250 more for a 3.75 -3.875"stroke combo to about $1000-more for a 3.875 and up to $4000 more if a aftermarket block and 3.875"-4" stroke combo , is built, but the larger strokes like 4" are built much easier with aftermarket blocks that have more room and thicker cylinder walls, I tend to stay with a 406 displacement with a chevy 400 block. plus those block are MUCH stronger and have thicker cylinder walls and larger cooling passages

the steam holes are holes drilled in the cylinder heads lower surface to match the holes in a 400 head gasket

400 BLOCKS:
Steam holes are recommended for all 400 block applications. Use a 400 Gasket as a template and drill the three holes, nearest the spark plug side of the head, straight down. The other three which are very near the head bolt holes should be drilled at a 30° angle away from the bolt hole. The center hole will intersect water about 1" down and the two outboard holes to a depth of 2 1/4". Use 1/8 drill.
best advice,....have a quality machine shop drill the holes for you, if you do it wrong the heads are junk, if ( they do it wrong THEY buy new heads!!!)


http://www.worldcastings.com/docs/03catalog/motownblock.pdf

http://www.flatlanderracing.com/dartironblocks.html
 

·
Registered
Joined
·
1,170 Posts
I like the 383, torquey, reliable, lots of hp.

Ask 84GRANDSPORT how He likes His!:thumbsup: :smokin:
 
1 - 7 of 7 Posts
Top