which engine block do you prefer for xxx-large BB?
talking about 650+ cu inches..
gm performance? p-no?
other? brand? p-no?
thnx.

Olds DRCE block.

max bore :4.7 am I right?
is there a limit also for crank stroke?

11.625 Merlin is tough to beat. I know 638" is MAX for a 10.20" Merlin II.

Yea, it looks like 4.7 is the max bore. I know that the cam is raised, the increase in displacement must be comming from the stroke. Looks like you can get a 10.7 inch deck with the aluminum block.

There is a "All star" engine also. I can't seem to find the brochure, but if my memory serves me that engine was 700". I believe that it used a billet block and heads.

slingshot is now the proud papa of tripple 705cid 1200hp beasts

timucin:

Merlin
Dart
Rodeck
Keith Black
CN Blocks
Trickflow
Arias


Something that needs to be considered in 650+ cubic engines is the bore spacing.

The bore spacing in a stock big block Chevy is 4.84 inches. The bore spacing in the Olds DRCE2 block is 4.9 inches, which is the maximum legal limit in NHRA pro stock racing for which that engine/block was developed. IHRA pro stock (known for Mountain Motors)rules allow a larger bore spacing, 5.0 inches. Trickflow, manufacturers a 5.0 bore spacing block, which has been punched out to 700+. I think the All Star engine also supports the 5.0 bore spacing, but the engine is more proprietary.

The larger bore spacing reduces the shrouding of the valves.

Crankshafts for the 4.9+ inch bore spacing are more expensive.

Most of the large cubic inch engines are aluminum blocks.

vtec

I know you are looking for engines based on the BBC but with the limits imposed by bore spacing, valve shrouding and general valvetrain torture, it makes you appreciate the Torque V12. It has 4.5 X 4.5 cylinders like a 572, but 50% more of them for 860 CID.

If a reliable 600 - 650 HP is possible with a hydraulic roller BBC in the 502 - 572 CID range, then a reliable 900 - 1000 HP is available in the V12. Does anybody know why Mercury chose to back the Allstar engine instead of the Torque engine?

Tomcat,
How many cylinders do you want to maintaine? if you need a rebuild and are running twins well that comes to 24 for the Torques and only 16 for the Allstar 708. Thats less to machine, balance, assemble, fail, ect ect ect. Easy choise in my book. Not that the Torques aren't awsome it's just the Allstars make more sense. Remember Merc has to think about cost to manufacture.

I know where a fresh Donovan BB is