will a 4.625 crank kit work with 3.750 jugs? I am looking to build something I don't have to rev like a chainsaw to get it to move. right now, the power is up way too high on the tach to actually use (accellerating at all from 70 requires a downshift or two). I would like to build one that makes a lot of torque in the 2000-5000 range. any input will be appreciated.

 

more feasible to go with 4 3/8" stroke flywheel and use 3.875" bore for a 103" motor. lot of them out there.

many have used a 4.5" stroke with the 3.875" bore to get a 106" motor, but with the longer strokes, the issue of shorter piston skirts required on pistons has led to some having issues with piston rings failing, etc.- the smaller the bore, the more the problem. going with the even longer stroke of 4.625" would probably really play havoc with the pistons, and probably require you go to at least the 3.875" bore anyway - or larger - or come up with a set of taller cylinders - starts to get involved unless you just go to the 103" or can use something like head-quarters 4.065" bore or a larger bore from axtell or s&s, and then you are still looking at custom pistons on any stroke of that length.

you don't need that long of a crank stroke to get you more power in the lower rpm's anyway. perhaps a simple cam change that gives you power in the mid to low rpm range would be very appropriate and a better starting point. i would look at the time proven 103" combinations if i wanted a stroke longer than the stock 4". otherwise you are going to have to go really big.

a nice 95"-98" set up without going into the lower cases, with appropriate cam change,higher compression, nice set of appropriately ported heads to match cams and compression,programmable ignition, air intake upgrade, and exhaust upgrade - will give you plenty of torque unless you are wanting to drag race. be a lot cheaper too.

also vastly superior to go with complete package that is proven compatible. that means cams, compression, head porting, ignition, etc from one single source that has a proven performance and who knows the parts match up. there are few such packages out there with the 4.625" stroke cranks. examples: head-quarters, hillside cycle, gmr performance, kingofcubes,big boyz...

 

I really appreciate the input. I am probably gonna tear into it next winter, so I still got time to make up my mind. I just ordered the lower (1.70) Primary drive kit to see if that will help some. will keep yall posted.