High RPM Hemi Rods

I was gonna ask that very question! My guess is at 9,500 RPM's plenty! But most of these guys are twisting 10k now so...who knows???

 

The reason rods break is when you balance a V8 engine it's a toss up, Because you have to use bob weights, Most engine builders balance using a formula of 50%, A V8 engine cant be balanced perfectly like a straight 6 or 4 Cly engine, Where bob weights are not used because the trows are at 180 degrees from one another, So when i was building engines I had a Lemco engine/ drive shaft balancer, it had saddles on each end of the main bearing surface's, When the crank was spun it rode on bearings in the saddles if the crank was out of balance the saddles would rock back and forth and there were dial indicators on each saddle so i could see how much the dial indicators moved, i would get the dial's not not move 0 degrees, An engine that would only rev to 8.500 RPM, I used the 50% rule, any thing over 8.500 rpm's i would use a 52% bob weight. My balancer had a variable speed that would spin the crank any where from 1.000 RPM's to 9.000 RPM's the reason the rod's break after 9.000 RPM's is because they start to shake and go into a harmonic out of balance if it's balanced with the 50% rule. So if your going to rev to more than 8.5000 RPM's you should have your crank balanced to the 52% rule. Just saying, Gene Terenzio Sr. PS I'm a ferm beliver in supper lighting the small end of the rod and the pistons. add 4/5 grams for oil.

 

Frank, your balancer spins the crank and bobweights at 9000 rpm's? I wouldn't want to be nowere near that machine if a bobweight came apart! I balance at 52% on everythihg that operates over 7000 rpm's. I friend of mine has a Superflo Dyno, and looks at the water in the dyno reservior when making a pull. He claims on a well balanced engine the water never gets choppy, but on others the water will make small waves and ripples. Not scientific but he has pulled thousands of engines.

 

Well you can call me Ray, Or you can call me Jay, You can call me Andy, Or you can call me Randy, But you don't hasta cal me Frank, cuz my name is Gene. I never spun a crank at 9.000 rpms, The variable speed will spin to 9.000 rpm, but I ain't no dummy, Most I ever spun one was to 5.000 and i was s#!ting my pants. Think about it if you use .004 Clarence on the mains and the dial is moving .005, What do you think will happen? I like the water thing, Good idea. Do you add for oil? It's like what Timmy told Frank, Put away the hammer, Every thing has to be PERFECT.

 

My mistake on the name change. I have a Sunnen that spins to 750 rpm's. I think most of the others spin at 500 are less. I add 5 grams for oil. I bet at 5000, that crank with bobweights flying around looks pretty angry.