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Reply to "After market 351 Cleveland Blocks"

At this point in time … I see three choices.

(1) Up to 450 bhp, 3.50 inch stroke (with up to 6.00 inch rods), 8.0:1dynamic compression, and/or a 6500 rpm rev limit any OEM 9.2 deck block will suffice. Two bolt mains or four bolt mains doesn't matter. Two bolt main caps don't "squirm" until some rpm above  7500 rpm … well beyond the limits of other parts of the reciprocating assembly. The production block's limits can be "stretched" a bit with parts like round skirt pistons and longer 351W rods with heavy duty fasteners (D6OE-AA  forgings with ARP fastener kit 250-6404). The 351W rods require pistons with custom 1.492 compression height.

The big problem with factory blocks is that in decades past everybody automatically bored them to their limit (4.030) during the first rebuild, thus no room was left for future (secondary) rebuilds. BUT blocks like that can be dry sleeved and honed back to 4.000 bores. Thus sleeved those cylinder walls shall be of better quality and durability than a those of a block without sleeves.

(2) If you're considering purchasing a heavy duty block, or have plans for building an engine that exceeds the limits of the OEM block, then an aftermarket "Windsor" block is currently the way to go. Use a Dart block with 9.2 decks for 3.5 stroke, or 9.5 decks for a 3.75 stroke.

(3) If you're considering a 4.00 stroke then my recommendation is a factory D7TE block (351M & 400 truck block) with almost 10.3 deck height. Those truck blocks have a "big block" bellhousing bolt pattern. Some folks prefer the earlier 351M/400 block with a small block bellhousing bolt pattern; those blocks are known as "FMX" blocks because they were cast for use in conjunction with the FMX transmission. While the small block bellhousing pattern is helpful for some applications the FMX blocks are not as heavy duty as the 1977 truck blocks.

Never omit dynamically balancing the reciprocating assembly and having the engine properly tuned. Also keep in mind factory Cleveland blocks need tappet bore bushings to "fix" their lubrication system AND they ALSO need steps taken to better lubricate the rod bearings. These are both lubrication problems, and thus related, but in actuality they are two different problems. Tappet bore bushings insure that plenty of oil is delivered to the main bearings, but they do not insure that enough oil is supplied to the rod bearing journals of a factory crankshaft.

Last edited by George P
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