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I've been offered a 400cc (destroked with 350 crank) SBC short block with high compression forged pistons, H-Beam rods, billet 350 crankshaft, splayed caps for $500.00. The question is can I order some high volume combustion chamber heads in order for me to run 8psi of boost or should I will need to replace the pistons. I will also need a special flywheel in order to use my T56 6-speed in that older block.
So what do you guys think????
I would be weary of gm oem 400's and boost. But find out what the piston specs are. They look like pretty big domes. You can still find 72-76cc aftermarket castings for heads that will help lower things down. Destroked helps lower compression too
I would probably run a set of 72 cc heads with those pistons. Even though I have run 64 cc heads before with forged flat tops with no issues until I put too much timing in and popped a ring land.
I do not have the heads yet, so I'm open to options in that area. What concerns me a bit is the cylinder wall thickness and cylinder to cylinder thickness also. Another thing I have to concider is the possibility of concrete filled water jackets which is a definately no no in my case since it's purpose is for 20-30 races with boost. If I do buy it I am planning on replacing the pistons with some flat heads or dished style heads and new bearings plus rings. Another think to concider is that I'll probabbly need to balance the rotating assembly with the McLeod flywheel designed for late motor models with newer T56 applications.
I'm not sure how well this will live in your application. Its not like its a 10 sec drag race. 400 blocks are known to run warm and are weak. Few psi on a good heads cam 400 is making good power so not sure if it will like that for long term runs or not.
I guess some dirt track oval track guys may have had more experience with production 400's. Could try searching
Hmmm...
Here is the thing, I do have a 1pc rear seal, four bolt, bare 350 block bored over to 4.060 which was bought brand new (remanufactured), which I guess it was done with a hand picked block that had sufficient wall thickness for the boring, assumed... This means that I dont need the Mcleud flywheel and keep the extra $450.00
I also do have a brand new GM Performance crankshaft for that block, but I still need the pistons and rods....
I guess that when I am writting it down I am answering myself, what do you guys think?
i wouldn't touch that engine with a 10 foot pole. It needs a full rebuild based on the pics above IMO. Some would clean it up and run it but I wouldn't. If it was allowed to get that dirty and rusted up, who knows how it was machined/built.
If you can get if for free or wait to pay until you tear it down - pull it down, clean the block and all parts, measure all the bearings and fits, and maybe get lucky and reuse most/all of the parts. Otherwise i would build the 350 block you have. I deal with spare machinery and "known to be good backups" for a living and 99% of the time they turn out to be junk when torn down and inspected.
To be honest the only things attractive to me about this block are the crankshaft and machine shop work on the caps, but the crank needs a special flywheel.
Brodix offers a few head's that are 80cc's for sbc. For the cost, I'd buy it! The cost of a flywheel vs. A short block. ... with forged internals, hmmmm, Yeah I'd buy it & will if you decide not to.
Let me know
08-11-2015, 09:02 AM
