ok i tore into the 400 i just got in a previous thread. i pulled everything and i am down to the mains and crank. i tried to grab the snout and rotate the assembly, but it wont. i tapped on a counterweight, and it moved, but its putting up alot of resistance. what would be the best way to take the rest of this apart.

things still on the motor: mains, oil pump, pistons and rods. how do i get them off (what order) to not damage anything?

You will have to pull each rod and piston out one by one. Somehow try and rotate the crank so that a rod cap is visible with both rod nuts. Remove the nuts and then remove the rod cap. Tap the rod and piston out each hole and then turn the crank over to the next one. After all the rods and pistons are out, you can remove the mains.

heres the verdict so far, i pulled the pistons and i had broken rings on 6,7,8. i had 2 spun bearings on 3,4. that journel is pretty chewed up, but everything else looks fine. with all the rods free, the crank still turns pretty tough. going to go pull that next.

the crank also doesnt look cast?!?! did these motors come with forged cranks? i am going to go grab a mic and see the bore size next.

the crank also doesnt look cast?!?! did these motors come with forged cranks?

To the best of my knowledge, GM never used a forged crank in the 400 as there was no need for it. It has 2.65" mains vs. the 350 at 2.45" and was made out of nodular iron. I've run the same 400 crank in two 400 builds and thus far it has held up great. These cranks are pretty tough customers.

Have you have loosened all the main caps? If all the pistons and rods are out, you probably have spun mains also,, and/or have a cracked/bent crank, broken main web or something more serious. There were no GM forged 400 cranks. In fact, as far as I know there was only one GM 400 crank, the 3951529, and it's cast. The good news is you can buy a brand new Scat 9000 400 crank for $230

Spun bearings= BENT crank.

ditto with jake. the heat warps them. can be straightened if not to bad and by the right person operating the tools,, if the heat or pounding didn't crack it........ for the cost,, a new aftermarket crank might be better. block might be toast from what you say. maybe able to line hone it though. all depends.

it didnt spin any mains, so i guess i am just looking at getting it machined and a new rotating assembly. hopefully the block is good.

i just rebuilt my 350 which had a spun bearing and wrecked my crank but i was able to find a local shop which took my old one and gave me a new one for $150 with all the bearings. idk if there is a shop around you that offers that but i'd look around for the best deal. for me it was better to buy a new one then have mine machined.

http://cgi.ebay.com/ebaymotors/NEW-SB-CHEVY-400-EXTERNAL-EAGLE-CAST-STEEL-SBC-CRANK_W0QQcmdZViewItemQQcategoryZ33616QQihZ013QQitemZ230134074775QQrdZ1QQsspagenameZWDVW

yall need to be introduced to the magic of ebay

my combo as of now includes the new afr eliminator heads, a roller 286 comp cam, 10:1, and a super victor intake. do i need forged parts or will cast do? what if i want to squirt 150 shot?

if that crank will be fine, i will just get that. should i get forged rods and pistons?

it didnt spin any mains, so i guess i am just looking at getting it machined and a new rotating assembly. hopefully the block is good.


Do yourself a favor and get the main caps checked for play just in case. My first machinest I had was suposed to aline hone my mains when he studed the mains and it turns out my main caps could rock even when they were toruqe down to spec. I didnt spin any main bearings but you really need to have this checked out anyway.

If you plan to race it hard or beat on it, get a forged crank. Don't cheap out here, it could cost you the engine, IMHO.