Offset grinding crank ?

[Larry Hill]

The center-line of the crank pin is moved .0065 away from center-line of mains. If stroke on stock crank is 3.483'' instead 3.480'' and the pin is on the high side of tolerance it will make a stroke of 3.493'' grinding it .010'' under to the low side. But usually it takes a .030'' under on the rods to get .013'' stroke. If the index is good why not make it .014'' long?

[Dave Casey]

Larry has it correct , it is a math exercise. The one thing that you also must realize is that indexing can not be fixed much by grinding. As an example, a 3" stroke crank would take a move of .026 for each degree it is off. to move it that much, it would need to be ground a minimum of .052 under.

[orangemonster]

Would you then have the rod journals chrome plated to build back to a std bearing? Or some other method. And would it be worth offsetting to a shorter stroke, if allowable to gain piston to valve clearance so as not to sink the valve job,in a piston without valve reliefs?

[1347]

I never heard of anyone hard chroming a crankshaft to bring up a surface thickness. I thought it was like nitriding, to give a harder surface so the bearings doesn't bite into the journal.

[orangemonster]

Maybe for both.About ten years ago I had picked up a crank from a still active today Stock/super stock mopar racer and it was offset ground and hard chromed journals to standard bearing size.

[Daran Summerton]

I once did a back to back on a bracket car. 355 vs 383 sbc everything equal. 355 ran 6.80 - 383 ran 6.80. 1/4" made no difference.

[Paul Precht]

Originally Posted by Daran Summerton

I once did a back to back on a bracket car. 355 vs 383 sbc everything equal. 355 ran 6.80 - 383 ran 6.80. 1/4" made no difference.

I did that in 74 with a 426 street wedge and a 383, same heads, cam, carb and the 383 Torker instead of the 440 Tarantula, the 383 was used after I spun a bearing in the 426 so I could still bracket race every week while I built a new engine. The 383 had almost a point less comp. and about 80k miles on the shortblock, it ran within a tenth and a mph of the average of the 426.