Using a stock animal crank...

Its an indication . The only thing is it's also after the fact . So possibly collateral damage .
Just a quick thought . Maybe mic the old bolt length. Vs a new bolt length.
 
J-Remy, we're not talking about flathead limiteds where you're replacing the rod and piston with similar weight aftermarket parts to the original factory balance. The little stock stroke animal crank doesn't have the big counterweights that the flathead crank has, and the bad rod angle now connected with a longer rod and big piston only makes matters worse. The problem is worse yet when it's is a big bore piston animal piston with a flathead crank. They were never matched together from the factory. We certainly don't balance everything either when it comes to single cylinder engines because you are basically just moving the balance rpm up or down to get it out of the meat of the operating rpm. If there is no problem with the part or installation, then there is likely a severe balance issue. Entirely possible and certainly can/should be addressed.
.001" is NOT ENOUGH clearance at the big end of the rod. You might run that on an intake valve guide but certainly not on the crankpin. Get yourself some plasti-gage and measure your clearance - don't guess.
 
Isn't part of the purpose of the flywheel to "counterbalance" the "out of balance" created by the rotation of the counterweights on the crank? If it matters, I've been using the ARC 6600a super lightweight billet flywheel, just thinking out loud...but maybe it's not heavy enough to counter balance the stock animal crank at high rpms? And subsequently vibrating the rod abnormally to the point its beating the rod bearing inserts to the point they're going out of round, causing the rod bolts to unloosen ultimately leading to catastrophic engine failure? Again, just a hypothesis...😳
 
Thats true .
Especially if it's balanced for animal components vs the flathead crank and attending parts . Crank support's could help as well.
 
flattop1 said:
Thats true .
Especially if it's balanced for animal components vs the flathead crank and attending parts . Crank support's could help as well.
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Using stock untouched animal crank, stock length billet rod and .010 over stock size piston along with the lightweight arc flywheel...
 
spincycle said:
Using stock untouched animal crank, stock length billet rod and .010 over stock size piston along with the lightweight arc flywheel...
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It should be "close enough" to not be causing these problems then. We've built hundreds of engines (WKA animal, etc) with the ARC rod, stock crank, and small bore and never balanced them. No issues (at least ones related to balance) that I am aware of.
 
spincycle said:
Upon closer examination...the rod bolts that came loose has some aluminum threading in its own thread...like it pulled the threads from the bolt hole in the rod....is this a sign of something gone wrong? Like maybe the rod bolts had stretched, maybe from something gone wrong during the torquing process...or maybe some sort of defect in the threads of the rod? Sorry if I seem to be beating this one pretty hard, just trying to figure out what/where/how this happened, as to hopefully avoid it ever happening again...
Click to expand...
over tightening does that
 
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