caddytransam

I have a standard bore 400 chevy. It had only 60,000 miles and it spun a rod bearing. The block has been cleaned, magnifluxed, honed, and new cam bearings. I also have the crank which has been turned 10 /20......how much do you think I could get out of this. ......Thanks...

ME Leigh

Maybe $500.

Ward

iTrader: (1)

What type of 400 block? 2 bolt or 4 bolt? The 2 bolt ones are more desireable, since they are actually stronger than the 4.

EDIT: Forgot to ask, re you just talking about the block? Does it have any ridge at all?

camaro03

2 bolt stronger than 4, whats your reasoning behind that?

Ward

iTrader: (1)

Well, this is only true with a 400. Normally a 4 bolt block is stronger, though. A 400 block has larger journals than any other small block chevy, which means there is a little bit less material on the bottom of the block, where the main caps bolt to. Drilling 4 holes per cap in this area weakens it significantly. This is only tru for a SB 400, though, all other SBC's have enough material there to support 4 bolts. Can anyone else back me up on this?

camaro03

right now i have a 4 bolt 406 and the guy at my machine shop said those blocks were very rare and i was lucky to find one, and i know that i was lucky to have it given to me (my brother in law had it and it was blown up when i got it)i rebuilt it with all thats in my sig, the cam lift is inacurate, since then, i put a .5 by .52 cam, the rest is right

ME Leigh

Yes all 4-bolt blocks have a tendency to crack and break around the mains.

camaro03

i still think the 4 bolts are stronger

RB83L69

There's alot more metal in the webbing area of the block in the later castings. The later ones were set up for 2 bolts, the inferior early ones had the 4-bolt caps installed. It's not an issue of 2 bolts vs. 4 bolts; it's a question of early weak blocks that happened to be equipped with one thing, vs. late stronger blocks that came equipped with something else. Just sticking more bolts into not enough metal in the first place, doesn't do a whole lot for the ultimate strength of the assembly.

Yes the 4-bolt blocks are more rare than the 2-bolt ones (yawn); there were fewer produced in those 2 years than there were of the other type in the 7 years or so of their production; and that makes it a better part..... how?

Still, it's almost hair-splitting, at the street motor level. If you've got a motor with some mild little cam like that, any block is plenty strong enough. You're not going to have to worry about breaking anything. Those of us that do stupid things like make 434s out of them, with heads and cams that give more RPM potential, concern ourselves with such details.

Last 400 core I had cause to buy, cost $250, for just a whole core motor. (It was a 2-bolt BTW, to make into a 434) So $500 is probably a bit aggressive for what you've got, but not out of reason, depending on your local supply & demand situation.

Cam28_boy

any of you have some main caps for a 4-bolt 400?

85TPI400

I see them for sale on ebay all the time!

RB83L69

http://store.summitracing.com/partdetail.asp?part=20797

camaro03

So what you are saying is chevy made a 4 bolt block to make it weaker? that makes alot of sense, i am not arguing that i would break anything, im just saying a 4 bolt main was made like that for a reason, otherwise there would just be two bolts.

RB83L69

The 4-bolt blocks were the early ones. I guess they learned a lesson: more metal, but fewer bolts, made a better product.

Ward

iTrader: (1)

They didnt mean for the 4 bolt block to be weaker. On every other SBC engine, putting 4 bolt mains on it would make it stronger. So GM decided to make a 4 bolt 400, without realizing that they were removing so much material from the bottom end that it actually made it weaker. Engine design in 1970 (first year of 400) was not what it is today. With today's technology, engines are designed and tested on computers before the first block is ever made, which basically eliminates design flaws (If anyone knows about LS1 'piston slap', then they'll know why I say basically :P ). Back then, it was more of trial and error, using an existing block, and changing bore/stroke values. For a stock motor, you probably would never have a problem with a 4 bolt 400. But if you are looking to build a strong 400, they're not really worth the effort. I'll stick with my '80 (last year od the 400 :P ) 2 bolt 400.

VERTIGO Z28

iTrader: (1)

Block strength is determined by the nickle content not how many bolts the mains have. On our street stock 406 we have splayed main caps with 4 bolts this motor is good to 9500. I would not trust ant 2 bolt block to do that. Most 4 bolt blocks were put in vehicles where they would be under extreme conditions.I.E. School busses Work trucks and MUSCLE CARS. So go figure that boyz and girlz.

Mark W. Winning

The 2 bolt IS the better block for the 400 series. Kevin, you said the magic word, splayed, that means, not STOCK. The reason people go after the 2 bolt block for high HP is to be able to splay the mains. High nickle content will do nothing if you drill holes in an area that is already thin to begin with.

I have bought 2 400 2 bolt short blocks for 200.00 each.