73 340 vs 72 and earlier 340

[bbscamp]

I have a 73 340 (cast crank), that I was told was running years ago, but pulled for a BB swap.  I need a 340 for a 69 Dart project.  The dart currently has a 318 mounted to the 4 spd.

I was told the cast crank 340s are externally balanced, and that I would need to get a balance flywheel to match it.  Is this true?  If so, whos a good source to get one?

Also,  performance wise, how does the cast crank stand up to the earlier steel crank ones?  any enlightenment you sages can impart would be appreciated.

THANKS
 - - - oh yeah...anyone have a 69 340 they want to part with?   

[vinb]

Late '72 340 and all of '73 340's are cast cranks and are externally balanced engines, also the '74 360 is too, but you will need the correct flywheel for the late '72/'73 engine, even through the 360 is also external balance,  that will not work (believe me I know) different wheel. If you come across one extra, I still need a '72/'73 340 flywheel. The one I had the heat cracks did not look good after resurfacing it.. Let me know.
Anything earlier is internally balanced and you can buy them just about anywhere..
Good Luck.....

[72bluNblu]

The cast crank shouldn't give you any problems performance wise if you're just planning a street car under 400 hp. If you want street/strip or 400 hp + I would lean to the forged crank for strength...

[71chally416]

Actually the 4" stroker cast crank they sell has less strength than either the 340 or 360 cast cranks because the rod journals are spead farther from the CL of the mains.
There are a bunch of motors already out there making 500hp with them.  Don't think I'd worry about that unless I was gonna use large amounts of boost or Nitrous.

[LAA66]

 Not sure if it came from an automatic or not, but since the crank is going in a 4-speed setup you may need look at machining for a pilot bearing. 

[Topcat]

Weren't the intake valves smaller on the later 340? I know the earlier ones were 2.02.

[72bluNblu]

Weren't the intake valves smaller on the later 340? I know the earlier ones were 2.02.

Yup. '68-'71 ran 2.02" intake valves, '72-3 had 1.88's.

[Chryco Psycho]

I would use a steel crank from a 318 add a set of high comp pistons & rebalance the engine & have a real 340

[bbscamp]

OK Chryco....expand on that please!!   The oldest 318 I have in the shop is a 72....a running 318.   Should that have a steel crank?   what exactly needs to be done to do the conversion?  I"M interested!!

[rallyechall]

You want to find a 318-3 truck crank from I believe 67-71. It is a strong forged crank.

[Chryco Psycho]

A lot of 318s had steel cranks , most trucks do , use a replacement forged piston or a lighter aftermarket one & , you could use the lighter 318 rods with a light piston or swap to 360 rods & have the assy balanced . I would use a set of ported 308 truck heads for some decent power