Rare 400 SBC Question

I bought a pig in-the-poke .030 over, two bolt main 400 Chevrolet block a few years ago that had been rebuilt and soon after it had seized a rod bearing. Apparently the builder had put an oil pump in it that wasn't up to the job since the rod that seized was at the front of the block, farthest away from the pump itself. The reason I knew it was a recent rebuild was the pistons still looked fresh.

In doing some searching for 400 build tips I ran across a 1999 Chevy Hi Performance magazine article that said the rarest 400 was one in which the block was cast with only two core plugs per side instead of the usual three. Mine also has the casting number ending in "509". Supposedly these were stronger castings and sure enough when I checked mine was of the two core plug variety. My question is do any of you guys know why they were considered stronger? I read somewhere else that after sonic testing there are 400 blocks that will take a .060 overbore. Could I have one of these?

Your thoughts please.

 

2 freeze plugs per side = made after 1972 [ish]

.060 over??? Sure, with sonic testing

Rare? In the chevrolet world, that means less than 5 million were made.

Spun front bearing? Sounds like the builder didn't clean the oil passages very well.

 

don't know how rare but had one (same with two freeze plugs) in a 57 with early heads (drilled for steam/water holes) with a 4 spd--ran very very strong and NEVER heated up

 

Sonic it first for sure, maybe you only need to go .040".

 

Stock oil pump is fine for anything spinning a stock 400 rotating assembly.

You won't find enough power overboring to make it worth risking the block. Bore the minimum needed and save the rest for later. The vast majority of 400s can't go past .040 safely.

good luck

 

Not real rare but the 509s had less sand in the casting >>>>.

 

the 509 casting 400 is a higher nickel content block..it is the block for 400 building ..the only other one better is so rare it is just about unobtainable...60 over is eay with a 509 block...several companys (good rebuilders) sell 60 over 509 blocks and even give them 2 year warrantys...the down side to the other 400 blocks is the problems with cracks around the steam holes, which generally leads to blown head gaskets, espically when run hard....but this doesn't seem to happen with the 509 casting....been doing 400 sbc's for many years, sold them as remans for 2 years at a national parts store chain also...good block for sure, but as stated, probably wasn't cleaned propper and lead to bad oiling of the forward end of the engine..i have a 40 over 400 509 block, ran the snotch out of it for 4 years in a blown vega wagon.....drove it daily to work and everywhere....still have it, minuis the blower...probably end up in Lil Beast if i don't go hemi..and he's being built for my retirement tour of the usa....so i guess that's a good statement in how comfortable i am with the motor, willing to drive it cross country and back...

 

Or some Bozo simply ran it low of oil...

 

btt

 

What more do you want to know?

 

I suppose the main thing that bugged me was the fact that a magazine devoted exclusively to Chevrolets would infer that the two core block was so rare and not explain why. I greatly appreciated what you and others had to say particularly your comment about the high nickel content of the 509 casting. If thats the sole reason it's a better block then yay for me and the block I picked up for $50 but my opinion of the writing staff of Chevy High Performance just went down a few notches. While Jeff Smith was editor of that magazine I used to read every issue from cover to cover.

 

Each of the block codes had a different core/mold set. To the untrained eye they're all the same but there are subtle differences.

The early 400 reputation came about because some sand from those cores remained in the block due to changes from the siamesed bore. Loose sand in the cooling system equals torn up water pumps and a reputation for overheating in the first year of production. At this age all that sand has come loose and any good block is a good block.

Because of this there was an evolution in the core tooling and some alteration to the freeze plug configuration. All aimed at getting the core sand out of a freshly cast block. During several years the block was in production at more than one foundry, so more than one mold/tool set was in use. Not all mold/tool sets are exactly alike, even if they're "exactly alike". Some sets just generate a thicker or more consistent wall, even if it's not intentional.

If memory serves the 509s represent like 15% of all 400 production. So not overly rare to start with. And people have hoarded them for years so they probably survive in higher numbers.

Realistically, if you "need" a 509 block, then you actually need an aftermarket block.

good luck with the project. Don't forget to tell everyone it's a 350 and make em feel bad!

 

Shifty - as one old fart to another - You da man! Thanks

 

Absolutely!
This is the "new" 400 junkyard block and it's better than the GM part.

FWIW, how much money would you have in a junkyard 400 block by the time you had it vatted, fitted for 4 bolt caps, fitted for the one piece rear seal, bored, honed, and decked?

 

I was told the 2 bolt main 400s are stronger than the 4 bolt main 400s??

 

I'm more of a medium fart but the fact you'd think otherwise is quite a compliment. 400s are kind of a case study for a foundry guy that's also into chivvies. Good luck with the project.

 

I believe the 2 bolt mains caps are wider than the 4 bolt,also the 2 bolt allows you to angle the outer bolts when converting to 4 bolt caps.

 

i did up a set of 400 heads to run on a 350, i had flat top pistons and if i remember corectly the 400 heads had 68 or 70cc's giveing me 9.8 to 1, they had 194 valves and larger runners, been awhile i may be off on the cc's a little.

 

I have a '509 block that I'm building right now for my '35. It also was bored .030 but it cleaned up on .040. It spun a bearing because the oil screen fell off. I was actually buying the engine from a friend who was replacing it with an LT1 but before he could get it out the whole deal went south. Once I got it part I found the ever so famous cracks between the head bolt holes and the steam holes....It was running like a top and had no head gasket issues so I bored it .040, I'm installing Moroso 37800 deck plugs, going to use head studs and zero deck the block and run it. Naturally aspirated it should be just fine. the cracks are between two holes so they can't get any bigger.

 

The factory bolts aren't splayed and go into a thin area so there's a lot of agreement that the extra bolt holes end up harming more than the wider main caps help. Aftermarket 4 bolt cap sets are splayed outers and require custom drilled outer holes, so obviously the 2 bolt blocks are more desireable because you don't have unused bolt holes.

Another case of if you truly need 4 bolt, you need an aftermarket block.

The way it works is whatever good block you can get for your money, be it 2 bolt or 4 bolt or whatever casting number....if it's a good block buy it. At this age condition over-rides everything else. If you need more then you shouldn't be looking at stock blocks.