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I would take either 817 or the 509 is the core shift wasn't bad and stick with the 2 bolt for the 500hp range. 4 Bolts id be cautious when I passed 400hp. I have seen the entire crank pull out every stud in a 4 bolt. And yes it was studded not splayed though. But he was roughly 600hp and heavy on the bottle.
 
dont get too caught up in casting numbers, imo.
the most important thing with them is little or no core shift, and the 2 bolts are preferred because the main web is more stout than the 4 bolts. the best bet with a factory block is a two bolt block with splayed 4 bolt caps, no core shift. after about 550 horse or so (yes many people have gone much more) i'd go with an aftermarket block.
unless a great factory std bore 400 falls in my lap (that would hafta hurt), my next motor will utilize a world or dart block.
as always, jmo.
 
I was the proud owner of a '509 block which I had owned for a number of years and driven it into the ground. I built my 406 around this block for two reasons. I already had one, and I was supposed to be rebuilding this engine instead of heaven forbid buying another race car motor (otherwise I would have opted for a Dart Little M or sportsman block). I have included a portion of my build sheet for the motor covering machine work for reasons of comparison. The costs in your area may vary.

Cost for Machine work at A&S Motorsport Riverview (Paid $800 deposit 26May05)
Strip old block (freeze plugs & dipstick tube) 26.00
Bake old block at 650°F for six hours 68.00
Magnuflux™ for cracks 35.00
Install splayed cap steel main cap: align bore, and then align hone block 400.00
Deck square 0.015" 120.00
Bore my old 400 SBC stock 2 bolt main block 0.030" over with deck plates 160.00
Install cam bearings 30.00
Tap three front oil galleries for pipe plugs 10.00
Drill steam holes in heads 30.00
Hand wash block and steam clean 20.00

Total $899.00
Dyno cell time averaging 8 pulls (includes break-in and set up) $375.00

Below is a note to myself as I was shopping around for machine shop services in town. Gil is the proprietor and has five Wally's on the wall along with three framed NHRA SS national records from motors he has built (though most of his business comes from that other sanctioning body Nasfar or something other claiming to be stock cars).

Gil at A&S doesn't recommend Milidon main cap conversion on the 400 SBC because there is sufficient main cap restraint provided by the bottom end girdle to support up to 500hp. Recommends 2 bolt block over the 4 bolt block because of increased nickel content in casting makes block stronger, and has more meat in the main webbing than earlier blocks. The '509 casting is the best (has only two freeze plugs in side of block); but '817 casting (three freeze plugs cast in side with only two actually machined for use) is his next best choice.

Larger Dave (Satisfied Customer)
 
Mark .L.W. said:
I went with the Dart litte M with the billet caps , after looking for a good block and still not finding one just spend the money and be done with it .
Mark .

Wise choice over the 30 years building engines and machining blocks we have seen more issues with the 400 blocks then the dart and Bow-tie blocks at our shop we can probe the blocks out for cylinder locations, lifter bore locations and cam tunnel location and from what I have seen on these blocks the after market blocks are a lot closer to blue print which in turn will make more power over a stock block that is out of blue print.

The last 400 block we machined with all the bells and whistles ran 1295.00 and for 2395.00 you can buy a Dart all machined ready to go and is much more dependable then any 400 block.

Before machining on a 400 block spend the extra money and have the cylinders sonic tested for thickness as we have seen some issues with those blocks in that department.
 
Mark .L.W. said:
In one article Joe Sherman did , He said two motors being the same , the one using the Dart block made around 20 HP more than the stock block did .
I can under stand that happening.

Thats good info thanks
 
Mark .L.W. said:
In one article Joe Sherman did , He said two motors being the same , the one using the Dart block made around 20 HP more than the stock block did .
I read that artice somewhere myself. But if your buying it to gain power your not getting the best bang for your buck. The power gain is just a added benifit. 20hp for $2000.00 is expensive for street/strip hp. A Prostock engine is a whole different ball of wax. The idea of the motor staying together is the reason for paying several grand for the block. IMHO
 
Consider this: How many ol' Chevy Impala's (70-73) do you see still around w/400 engine still going strong? I saw one (impala) couple days ago but there everywhere here in the South. I have a built 400 4bolt main also that does just fine.
 
Never mind the Impalas, Estate (trailer park) Wagons; I've never seen one with out 400 emblems and they are everywhere here also. Have to go out to the more rural areas, but there are one or two in every trailer park.

Not so politically correct
Larger Dave
 
There is nothing wrong with most of the 400 blocks , but when you start pushing them up into 500 horse area you need to spend some Money on them . After doing this We are just saying sometimes its just better to go aftermarket , after preping a stock block and then comparing to the price of the aftermarket piece sometimes there not to far away .
Mark .
 
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