Originally Posted by cs89chevy
a guy around my way has two blocks that have been through the necessary machining and reassembled what im asking is what would most of you racers go with the 383 is a fresh 30 over 350 block with a 400 cast crank external balanced with 400 rods forged flat top pistons
and the 406 2 bolt block cast crank 10-10 5,7 rods cast flat top pistons decked .10 both for around the same price would really love to have some help with this guys
Wow, thee are still too many variables and too many questions to be answered before making a call on either one...
1st: When you say a 400 crank in a 350 block, with external balance, I am assuming it is a good after market stroker crank and not a cut down stock 400 crank...?
2nd: I have never heard of 400 (5.565") rods in any 383 combo...? I don't think you could find the correct compression height pistons for that...? Most assemblies have either 5.7" rods or 6.00" rods.
3rd: if that is true, and you have a 4.030" bore, with 3.75" stroke, and 5.565" rods, the short rod/tall compression height "forged" pistons would be incredibly heavy... a scary excessive balance risk...?
4th: If the 400 block is a true "406" (4.155" bore x 3.75" stroke), with 5.7 rods, that combo would be much lighter piston weight and easier on the rotating assembly.
The only real difference between a 383 and a 406 is the bore size, 4.030 vs. 4.155. Either 5.7" rod/piston or 6.00" rod/piston rotating assembly combination should be pretty much equal parameters between both blocks. Howerver, what 400 block number is it, that may be a critical factor? You can scan these forum threads for many arguments over different 400 blocks...
I have heard many arguments that a stock GM 2 bolt main frame with cast crank is more flexible and less prone to 'snap' under hard load/unload...?
You really need to tell us the application and intended usage before anyone can make an educated recommendation... JMHO...