Crankshafts, we need crankshafts

tarior

The #1 part for the AMC V-8 that seems to be missing from the aftermarket is a good quality, yet affordable crankshaft (I love that word :wink: ) Callies will custom make one for about $2200, but it would be nice to just buy one off the shelf for about 1/4 that price. Yes?

Lifted79CJ7

=D>

bushwackertn

I'll be needing a crank shortly myself, and I'd rather not have to use the stocker in my 360.

tarior

Yeah, and I don't know of anyone selling an AMC crankshaft :mrgreen: for under $2000. :smile:

Holeshot

Hi....I've been using AMC engines for over 25 years now, and have never destroyed a crank. Have to have one turned every 20 years or so, though. You guys been using those off-brand boat anchors too long. Useable 401 cranks go for around $200 on Ebay, what more do you want??? On another note, Speed-O-Motive will offset grind (428 cubes, 434 with + .030" overbore(as I recall)), fillet radius, nitride, cross-drill, & lighten YOUR 390/401 crank for about $1000. Sad thing is, you will actually LOSE horsepower (according to Dyno 2000) as you increase stroke, but you can gain a whole 20 or 30 ft/lbs of torque. Whooopeee!!!!!

tarior

The main problem I see with using a stock crank, even one that has had the full treatment, is that it is between 14 and 40 years old, and has been flexed a few million time already. Anything metal has a finite fatigue life, and I would hate to start a race motor project with a crankshaft whose life might already be more than half over. I'm not talking drag racing, but sustained high rpm (over 7500) operation.

bushwackertn

So, it is possible to use a 401 crank in a 360? If so what all has to be done ? I would consider it, if it's not to much trouble.

Holeshot

Flexed???? Have you ever seen a 401 crank??? I hardly think there would be ANY flex, and metal fatigue would not even be a consideration. If it passes all the pre-machining tests, it's a go. I've NEVER heard of a 390/401 crank breaking, though I suppose there must have been one. If you are building an engine to make over 1000 HP and last a while, cost better not be a concern, and maybe you had better use an aftermarket crank anyway.

Holeshot

...in addition, if you are getting a crank out of a run of the mill 401 Jeep, it has probably never seen 5500 RPM and has lived its life with a very low compression ratio, never coming close to stressing the crank & rods.

Here's the specs I got for offset ginding a 401 crank:

Magnaflux, offset grind 401 crank to SBC SJ 2.0" (3.93" stroke), 1/8" filet radius, nitrate, nitride, knife edge, lighten, internal balance $1,050 at Speed-O-Motive

As far as using a 401 crank in a 360 block, all of the AMC blocks (68 & up) have the same main journal size and bore spacing, so I don't know why a 401 crank would not fit. But I think the 401 block has thicker webbing, making it stronger. I never considered using a 360 block since 401s can be had at a fair price.

tarior

Don't take my word for it, ask some of the other guys on the forum, ALL crankshafts do flex, granted, it is a very small amount, but it is flex. As far a breakage, there are plenty of sob stories over on the AMC forum from pretty experienced builders breaking their motors. Point is: the 401 well WILL dry up, and much sooner than any of us would like, and I for one would like options other than $2300 custom billet cranks and $4200 ICH blocks, wouldn't you agree?