I have just bought a 2 bolt, standard bore 400 to build up.
The casting number is 3951511.
The info at the Mortec site says:

3951511....400...70-73...4...Some replacement blocks had 2-bolt main caps


So it says its a 4 bolt, but some 'replacement blocks' were 2 bolt. Mine is a 2 bolt, so my question is, what is a 'replacement block'???

Thanks!

 

It's an over-the-counter block, not factory installed in a car. Used for warantee work, etc. Joe

 

Thanks, makes sense.
Does anyone have any experience with the '511' casting?
Is it one of the better ones?? Fingers crossed ;-)

Ben.

 

I have the same casting number on my block and it's a 2-bolt block!!

 

I hardly vist the C3 section...

From what I have read, the 511 casting started out at a 4 bolt main. The replacement blocks were the 2 bolt mains. I forget the reason.

I'm getting ready to drop in my 511 4-bolt main into my 89

 

Years ago I used a 400 SB in my son's '66 Chevelle. He wanted to pass it off as a 350 so we specifically used the later 2 B.M. and it was internally balanced so it appeared as a 350 SB externally. I put an ARP main stud kit with a windage tray, cast 400 crank, 5.700 rods, 10.5:1 forged pistons, and a 230 x .480 cam. Car ran on pump gas (at the time) and cut 12.2's all day long at 3620#. One drawback, it was built on a budget, so I used #993 canadian heads and ported them big-time. I tried to get a friend of mine at the time (Bill Mitchell) to give me a couple of the original "Cast-iron Dart" prototypes, but they weren't ready yet. In any event the car ran excellent and was constantly in the winners circle. I shipped the head gaskets to Fel-Pro engineering for analysis, as my son used nitrous quite a few times. The gaskets
"hung out" for 4 years with no problems also. Car ran 11.1/11.2 on
the bottle with a Turbo-350 and 4.10-12 bolt rear.
Thanks, Gary in N.Y.
PS With todays technology the car would probably be deep in the
"nines" somewhere. The heads we used were really what I considered to "junk", but it was all I had with a large enough chamber, at the time.

 

Mine is a 511 block but with 4 bolt mains. Plenty strong,though I did use ARP bolts just in case.

 

Actually the 4bolt 400 Small block has a reputation for cracking main webs and the 2 bolt 400s are prefered to 4 bolt models. The 2 bolt can be converted to a 4 bolt model using splayed outer bolts that are stronger and less prone to cracking the main webs (this has been proven by sprint car users for years.) The 400 4bolt small block should never have a problem in a "street strip" application but for racing, I would go with an aftermarket engine block.

 

The 400 was intended as a perf. engine & the first ones had 4 bolts. They had trouble w/ ring sealing & decided not to use it as a perf. engine.
Duntov was looking for 400 C.I. due to GM policy of 400 max. C.I. for the mid size & small cars. See How the Corvette got the Big Block on my website.