Discussion in 'Classic Models' started by HAWGLY, Jan 15, 2010.
How many thousanths can a stock 74ci cylinder be bored before you lose dependabilty?
Several companies make .070" over pistons for 74 c.i. shovelheads.
Thanks Breeze,,, another question,, do you know what ,if any thing , has to be done to 74ci cases to put in 80ci fly wheels?
Hawgly; Sorry, I don't. I have a old flatside shovelhead that has 80" wheels in it, but they were in when I got it. The reason I know they're 80" is the 4.25 stroke, and timing marks that were peculiar to certain 80 in. shovels.
.070" over is alot of metal to take out of a cylinder, I know they make them that big but not always the best way to go.
Bore sizes 40thou and over will cause the engine to run hotter than normal.If it was my bike I would be sourcing new barrels
It depends on what year the cases are. You need to change the bearings to the newer type to put late shovel crank assemblys into late Pan/early Shovel cases, but I understand that there is more involved in putting them in early Pan motors. Truett and Osborne makes Flywheels that will work with your crankshaft parts and don't cost that much (about $385 new) you can get all kinds of different strokes, but you have to clearance the cases to put in anything more than 4 1/4" stroke as the crank pin will rub on the inside of the cases. I have put as big as 5" stroke in "Cone" shovel motors, and had 4 5/8" stroke wheels in a pan motor in the past, and it screamed!
cone shovel cases will accept any lower end (70-91).80" cylinders are 74"
+.060,so you can at least go there with out probs.
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