best 331 shortblock to get

bgoins · Mar 10, 2011

clement said:
take the caps off one with a cast crank thats been run hard and then take the caps off of one with a forged crank that has been run hard. cap walk is what breaks blocks.

So you're saying that a forged crank will keep you from breaking a stock block? I don't think I'm buying that.

clement · Mar 10, 2011

bgoins said:
So you're saying that a forged crank will keep you from breaking a stock block? I don't think I'm buying that.

crank flex and cap walk do break blocks. is there a point where the block will break with the good balance on a steel crank, sure. but when you have crank flex (like a cast crank with an external balance) and cap walk resulting from this the block will break with less power than it would if this werent present. much like an internal balance crank will with a good balance job will also help the block last longer than hanging a 50oz weight off the ends of the crank.

RangerJoe · Mar 10, 2011

I agree with most on here. I just went through it myself. I had a stock short block in need of a rebuild. I was looking at $305 in block work (tanked, bored, honed & decked), $400 in new pistons (.030 over), crank reground ($100) and my rods were shot from being run so long with loose tolerances (measured .040 clearance), so I needed new rods $200. Oh yeah, rebalance with new harmonic balancer ($200). Rings and bearings ($175). So, I was looking at roughly a $1400 306 with stock crank, and stock style rods and pistons.

I bought a Scat 9000 series 331 kit, rated at 550 FWHP for $1350 (Balanced with harmonic balancer and flywheel). $305 in block work, assembled myself, and I now have a $1655 331 stroker.

I knew the stock block would most likely not hold up to a lot of abuse at 550 HP, so I felt the 9000 series was plenty of internals. I don't see a need to overspend on one part when the other one will come apart too. My opinion, stock block can SAFELY support around 500ish HP with reliability in the realms.

clement · Mar 10, 2011

my buddy and i built a scat 9000 crank 347 for his 2800lb lx hatch. it runs 6.80s@102 in the 1/8 on motor. it makes 388rwhp through a c4 with a 6800-7000 rpm shift point. we pulled the caps off of the d4 block a month ago after running it for a year with arp main studs and no girdle. the caps have been walking, bad. this motor doesnt get run on the street often so it probably has less than 500 miles on it.

the year before last we pulled the caps off a customers d0 block 347 that runs an internal balance eagle 4340 crank since we were putting a k member in the car. it also has a probe main girdle w/ the same strength arp main studs as the cast crank 347. in his gt it runs 7.20s@97 in at a 3400lb raceweight and makes 430rwhp through a tremec, on the motor. 6800 rpm shift point. no cap walk, at all. they looked new. Hans Fuestel built this engine in 2001 for him and i installed it in the car. in 10 years its made 100s of passes and has around 20k miles.

the steel crank 347 has withstood the test of time with 100s of passes no sign of cap walk. after a year and probably 30 passes the cast crank 347 has been walking all over the place. so it isnt simply a matter of hp.

based on how the caps look i am betting the block with the steel crank will last another 10 years, yet i have my doubts about the block with the cast crank lasting another season.

bgoins · Mar 11, 2011

clement said:
my buddy and i built a scat 9000 crank 347 for his 2800lb lx hatch. it runs 6.80s@102 in the 1/8 on motor. it makes 388rwhp through a c4 with a 6800-7000 rpm shift point. we pulled the caps off of the d4 block a month ago after running it for a year with arp main studs and no girdle. the caps have been walking, bad. this motor doesnt get run on the street often so it probably has less than 500 miles on it.

the year before last we pulled the caps off a customers d0 block 347 that runs an internal balance eagle 4340 crank since we were putting a k member in the car. it also has a probe main girdle w/ the same strength arp main studs as the cast crank 347. in his gt it runs 7.20s@97 in at a 3400lb raceweight and makes 430rwhp through a tremec, on the motor. 6800 rpm shift point. no cap walk, at all. they looked new. Hans Fuestel built this engine in 2001 for him and i installed it in the car. in 10 years its made 100s of passes and has around 20k miles.

the steel crank 347 has withstood the test of time with 100s of passes no sign of cap walk. after a year and probably 30 passes the cast crank 347 has been walking all over the place. so it isnt simply a matter of hp.

based on how the caps look i am betting the block with the steel crank will last another 10 years, yet i have my doubts about the block with the cast crank lasting another season.

That is pretty interesting. But, that is anecdotal evidence. I would still not put a forged crank in a stock block.

RangerJoe · Mar 11, 2011

A year or two ago, one of the big mustang magazines (MMFF?) did two seperate, unrelated motor build ups in the same monthly edition. It was when Dart released their SHP block. They used a cast crank in the SHP block and a forged crank in their stock block build. This didn't make a lot of sense to me, but someone told me at the time that the SHP block was stronger and the mains didn't walk, so a weaker crank could be used. And vice versa, the weaker stock block benifited from a forged crank due to weak main caps.

Just food for thought I guess.

TokyoJoe · Mar 11, 2011

RacEoHolic330 said:
I know of a guy on corral that dynoed a 9:1 Dart 331/AFR 185 which made 415hp/410tq at the wheels. He built the engine for boost but it ran so well in N/A form that kept it that way.

A 9:1 331 made 415 to the ground? Must have been some sort of supercam involved.

I've also heard that a forged crank can survive more crank walk than a cast unit. But I wouldnt put one in a stock block regardless. Before I did something like that, I would buy 3 stock short blocks and keep spraying them or blowing them until I could save enough for something a little more bulletproof.

clement · Mar 11, 2011

RangerJoe said:
A year or two ago, one of the big mustang magazines (MMFF?) did two seperate, unrelated motor build ups in the same monthly edition. It was when Dart released their SHP block. They used a cast crank in the SHP block and a forged crank in their stock block build. This didn't make a lot of sense to me, but someone told me at the time that the SHP block was stronger and the mains didn't walk, so a weaker crank could be used. And vice versa, the weaker stock block benifited from a forged crank due to weak main caps.

Just food for thought I guess.

thats the point. if you are buying a crank $300 extra for steel is cheaper than an $1800 block IF you arent going to run enough piston speed or power to force the mains out of a stock block.

15 years ago we hardly ever split stock blocks, even stock shortblocks with power adders that regularly made 500-550rwhp. these days its much more common. i wonder how many of the blocks that people are using as cores were detonated (even though not cracked), making the casting weaker and they dont live because of it. just a hypothesis.

clement · Mar 11, 2011

bgoins said:
That is pretty interesting. But, that is anecdotal evidence. I would still not put a forged crank in a stock block.

im not saying that it will make a stock block live forever, but my personal experience is that the $300 extra for the steel crank over cast is well spent if everything else is done right. im not saying a dart block isnt great, but sometimes you gotta run what you've got.

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