Light bottom end

brushpuller

brushpuller

Thinkin...
Joined
Nov 30, 2008
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630
With all the talk bout high rpms, is anyone tricking out the crank? Like knife edging the crank(to help with windage) or cut/grind off material that isnt needed for stringth to lighten that big old hunk of cast? Maybe some are,but dont here much about it!!!
 
keeping the pistons light is a good thing, but I was under the impression that the goal was to add weight to the crank to maintain inertia to keep from falling under the turbo
 
heavycrank.jpg
 
Yeah that is true to a point...their is a point though that weight hurts rpm. It takes power to rotate that mass. If it was lighter that would be more power going to the wheels. IMO
 
the rods and pistons rob more power than the crank... lighter assembly accelerates quicker, but easier to fall under the turbo. heavier assembly doesn't necessarily rob that much power IMO, especially at the crank. knife-edging the crank and using a windage tray definately frees up power at higher RPM. but 5000rpm isn't what I'd call "high"
 
Yeah...i see what ya mean, like an old john deere with the counter weight. But if your turbo and gearing is right, then it shouldnt fall below it! It should spin out. IMO. I just think it would be much easier on the bottom end if it was lighter and as you said it would spin up faster.
 
don't really need to spin up faster in a pulling application IMO... tach it up and ride the clutch out. as you go larger and larger and higher in RPM, it gets easier and easier to fall under the turbo
 
Forrest Nearing said:
don't really need to spin up faster in a pulling application IMO... tach it up and ride the clutch out. as you go larger and larger and higher in RPM, it gets easier and easier to fall under the turbo
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Yes indeed unless you pull with an auto! Thank God for Goerends loose convertors!
 
counter weight the crank and lightening the rods and the pistons is what works the best
 
When you balance the rotating assm. then the counter weights weigh the same as the rods and pistons assm's bob weight !?!?!? Right???
 
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Alright coounterweight the Crank I have done then lighten the Rods but pistons I haven't lightend them removing material is going to make them weaker in my opinion. I think thats why you don't hear of to many people doing it.
 
i've seen the banks truck an the crank is knife edged prob for very high rpm ??
 
psmike said:
i've seen the banks truck an the crank is knife edged prob for very high rpm ??
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Drag racing is totally different then sledpulling... Racing you want as fast of acceleration as possible, in sled pulling the extra weight in your rotating assembly helps keep the motor going as the sled tries to slow you down, i.e. inertia
 
JFlagg said:
Drag racing is totally different then sledpulling... Racing you want as fast of acceleration as possible, in sled pulling the extra weight in your rotating assembly helps keep the motor going as the sled tries to slow you down, i.e. inertia
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Different engines need different requirements.
Manual add some weight, that fastest you will spin it will be at the start. The auto's you need to be able to accelerate.
 
I know theres a old Gasser Math for certain amount of grams taken off the rotating assembly means more horsepower and higher rpms I can't think of what it is. but im sure the rules go the same for in Diesel.
 
We had a knifed crank 12lb lighter will hurt you at the end of the track taking it out and putting in a stock one till we can get enough money for a weighted one that is 25lb heaver than stock I was doing weighted cranks and flywheels 25 to 30 years ago in garden tractors that we pulled make one hell of a difference at the end of the track I have a buddy that put a weighted crank in his super stock tractor last year that is all he did and now he is at the top of the class the motor stay's up in the opperating range now all the way down the track.lighten cranks are for dragraceing not pulling that is why we're pulling out the knifed egded one.you can lighten up the rod and the pistons all you want the not going to affect the crank balance the crank is a zero bance already.
inertia is one of the maine things to think about when your building a pulling motor.Not that good for the street and raceing.


Dale
 
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