what is the BEST 400 block casting to be on the look out for? 509, 511, 817 etc??? :eek:

Far as I'm concerned, the best one is any 2-bolt block that doesn't have core shift and will clean up at .030 or less.

Good luck finding one. I saw massive core shift in most of the ones I looked at. I even found one that had 2-bolt caps, but the outside bolt holes were drilled and NOT tapped in the block.

If I had it to do over, I'd buy an aftermarket block and be done with it. Better cylinder wall thickness, better lifter bore and cam tunnel positioning.

I'm with Schurkey on this one. When I did my 406 a lot of the "available" blocks were not good candidates for a buildup. Spend some more money and get one of the aftermarket blocks - especially if you plan on building a boosted engine.

Thomas

Locating a good SB400 core is becoming more difficult. The last year of manufacture was 80. If you don't mind searching around, I'm sure you will eventually come up with a good core. Also, I must agree with the above about spending a little extra and going with an aftermarket block, IF YOU CAN'T FIND A GOOD USED CORE.
But, to answer you original question, it is the general consensus of opinion that the 509 is the most desireable casting. In the past 25-30yrs, I have built about 25 SB400s from all castings and have never seen a problem. In my family, there are 4 SB400s. All are doing fine and none are 509 castings.
Also, I am now a firm believer (it took a while) that the best way to go is with a 2bolt block. For street/performance use, keep it 2bolt and buy a set of aftermarket studs, rather than use factory style bolts. I personally prefer the longs studs which allow the installation of a windage tray. If you MUST have a 4bolt block, use a 2bolt block and install aftermarket splayed 4bolt caps.

Best 400 casting to use is the one YOU have laying around. Assuming of course that it isn't worn beyond boring.