Contemplating a 400 CI build for my '62. I'd like to know the letters on the block that identify the 400 CI size. to make buying a used engine (core) more foolproof. I owned one of those years ago in a '76 Monte Carlo, with a stock two barrel it was not impressive (must have been too heavy). Thanks, /Bob

 

Here you go. '73-'80....330817 --- 2 bolt
'70-'80....3951509 ---2/4 bolt
'70-'73....3951511 ---4 bolt
I do not know if any one of these have any inherent issues, like overheating as has been mentioned over the years
Why not go for a 350 bored .030 over and make simply good reliable power. They are readily available for fair money and parts combinations are amazing. Dennis

 

This is good info but what I was originally looking for was the three letter sequences. ie: My '62 Vet was born with an RC engine (long since blown up). Seems either identification would accomplish the same results. Not sure why I am looking into this option as my current 327 runs fine and I have a "spare" rebuilt 355 sitting on an engine stand , just in case ! Thanks

 

If I remember correctly, a 400" small block had three freeze plugs per side instead of the usual two?

I also think all 400's have cast crankshafts instead of forged?

As Bluestripe mentioned, it may be easier/cheaper to go with a 350 instead. If you go with 400" plus,you would probably need better heads for better air flow.

 

If you look at the sticky on here with the “lime book”. It has all the Chevy suffix codes from 55-91. It might take awhile to locate all the 400 only codes but it will be definitive

 

Just paged through the Lime Book and realized i was making a very difficult request that would be tediously unnecessary. If I pursue this foolishness I will concentrate on the block #'s for ident.

 

well when you find the block get the numbers and just cross reference the lime book to make sure

 

Robert, you might want to do a search for posts by Tom Parsons (Forum member DZAUTO) as he has built up a couple of 400's that he's disguised cleverly and thinks very highly of the results. You could also send him a PM directly or wait a while, I'm sure he'll stop by shortly and answer any questions you might have about making a 400 into a terrific street engine.

Good luck... GUSTO

 

For a 400 block, the casting number is the key. The same casting was used for several different configurations that would appear in the letter sequence stamped on the pad. The previous post listed most or all of the 400 casting numbers, but I'm not sure the 2-bolt versus 4-bolt main info is tied to the casting number. At least some 400 block casting numbers were used in both 2-bolt and 4-bolt configurations.

Your reference to the 400 block possibly being "too heavy" is not the case. A 400 block weighs about the same as a 350 block. The primary difference between a 350 block and a 400 block is that the 350 had 4.00" bores and the 400 had 4.125" bores. The crankshaft main journals of the 400 block were also larger than the 350 main journals.

So, the 400 block gives you more displacement than the 350 block in a package that is exactly the same external size, and almost exactly the same weight, as a 350 block. The only down side of the 400 block is that they are harder to find, and far less common, than a 350 block.

Note that any 350 block can be easily stroked to 383 CID, and any 400 block can be easily stroked to 427 CID. For most people, the "sweet spot" in terms of cost is a 383.

 

My local mechanic and former stock car racer had several 400s sitting in a corner and allowed me to pick any one I wanted. I consulted with Tom Parsons ahead of time and learned much about them. Two or four bolt doesn't really matter, just make sure to have it magnafluxed. There's no reason to use original heads and a good set of 327 heads will work fine. You can use original crank but it's externally balanced so you'll have to use corresponding parts. I ended up with more horsepower than I originally targeted but the torque is amazing, you'll love it!

 

Last year I built a 400 SBC for my 56 Nomad. Scat and Eagle make fairly inexpensive rotating kits for the 400s.

Picked up a '74 vintage 400 block from a neighbor and I also thought all 400's came with '3' freeze plugs on the side of the block but as you can see in the pic, while there is a raised casting area where the middle freeze plug might be, in this block it was never cast with that third plug.
Mike T - Prescott AZ

 

Out with old 327/350, in with the new 406/540!

 

Your block looks nothing mine although I no longer remember what year mine is.

 

The 400 SBC was made between 1970 and 1980 and no doubt had a few variations in their castings. Besides my 74 vintage 400 having casting number 330817, there was also 3951509 and 3951511.
Mike T - Prescott AZ

 

Try this list..

 

Mine is a 3951511.

 

You probably know this, but I believe 400 blocks do not have the hole in the rear of the block that your 327 uses for crankcase venting...

 

I want to build a 406 too..Bob let me know if you find TWO cores.

 

just curious what kind of heads are those, twisted wedge? Thx

 

I see that you are in Massachusetts, and so am I. In the back of my garage, I have a standard-bore 400 block, casting number 3951509, that has been converted to aftermarket 4-bolt mains with the splayed outer bolts. My plan has been build this up as a 427, just because I think it would be REALLY COOL to build a small block 427 from a GM 400 block. I have most of the details worked out, based on a custom Callies crank that has the "Honda" 1.88" rod journals and Callies rods. This combination helps a lot with the block clearance problem and the cam clearance problem. Without these custom aspects, it's hard to get to 427 CID using a stock GM 400 block.

However, I already have a fresh 383 in my '67 that I built and installed a couple years ago, and I think that's all the power I need at age 66. So, even though I really want to build this 427 small block, I don't think I need to put it in my own car. I just want to build it and write an article about the 427 build (I wrote two articles about my 383 build).

So, if you are interested in a 427 small block, maybe we can work something out. I don't necessarily have to build the short block myself, but you would have to agree to use the crank and rods I have in mind, and also let me document the build for an article.