Well, Im very interested in finding who here has gone down this path and what have they found in terms in throttle response, balancing, reliability? Im not referring to simply polishing the counterweights, Im referring the the old practice (I believe Ansen in CA used to do it quite often for racers) of removing the two centre counterweights altogether and then proceeding to knife edge and lastly polish the remainder of the crank to throw off the excess oil then final balance. In this manner they would normally remove b/w 10-14lbs off the crank. Now guys pls no debates about whether its needed or not; what I really wanna know is has anyone here done it and what have they found? Thanx Rat
Really interesting topic Rat. Looking forward to reading the responses and seeing weather it's worth doing this on my upcoming Flathead project or not. HC.
Used to send out Honda cranks for knife edging when building 500hp turbo daily drivers and 100+hp per liter NA engines. Made a difference there, dyno proven to an extent. Tough to do back to back runs when swapping a crank.
See if you can PM av8 - Mike Bishop - he's been lightening cranks for a while. I've not done it, but plan to on my next one.
Hank the Crank in California provides lightening and knife edging and balancing for cranks. Very famous and high qulaity.
The engines I have built all have lightened cranks ,rotating assy's and the best description is the lighter the bob weight the quicker the throttle response. Less weight over all is good but I am only assuming it would be the same on all applications.Thats something you have to decide.
I've read articles from the fifties regarding lightening cranks. The pictures showed the guy cutting major amounts from the counter weights with a band saw. Sorry to say I don't have them in front of me or I could actually contribute to this thread. Flatman
I have been doing flathead crank lightening since the early 50's. Contrary to what most people have heard, the counterweights are NOT cut first...All the material you can cut is taken from the throw sides first. The leading edges are then rounded or knife edged. THEN, the OD of the counterweights is turned by an ammount that is eventually determined by the bob weight..This requires a couple of trial rough runs on the balancer. The center counterweights are NEVER removed. These are needed for torsional vibration suppression.. The eventual OD of the crank can be reduced by as much as 3/4 inch. This equates to much quicker spool up and better bottom end longevity. I have made many dyno pulls with engines with reduced OD cranks but never with and without in the same engine. Attached is a pic of rough machining the throw sides on a SCAT crank.
I didn't think Mike Bishop was "lightening" cranks per se, just polishing and detailing them. From what I've seen it doesn't look like what he was doing would have any significant effect on weight. Maybe Mike will come on and explain. He hasn't been around much lately. Frank
When you do this "stuff" for a living you get to see most of the racing "tricks"?? I would VERY strongly recommend against removing the 2 center counterweights on the Flathead shafts with these shaft's being supported by ONLY 3 main bearings, not a real good move, in my opinion!! We finally have most decent aftermarket "long-arm" Chevy cranks now using those center weights, they are a necessity with any 4.500" BB stroke. We believe they finally looked at these Flathead pieces and put "2 & 2" together! And here we now have 5 mains for support, not 3! There are numerous "safe" ways to lighten shafts, some mentioned above. Most will be "pendelum" cut which is fine! If you look closely at the OEM Flathead shaft it incorporates a "pendulum" type casting from the factory! Seems what is/was old some years ago, is actually "new" again today! Thanks, Gary in N.Y. P.S. Most people up here have no idea the amount of "flex" at the center main on ANY unit, the crank is literally like a "piece-of-rubber", moreso when running on high HP builds!!
Saw a video of a crank spinning, it's incredible! Looks like spaghetti. Really gives you a bit of trepidation when it comes to modifications, especially in an application like this, as in old tech which is rather borderline or obsolete judging by what we know now. Remember, the Ford V8 is one of the first motors that hot rodders learned on, and by "learned" I mean by breaking shit!
No, he was removing a fair amount of metal as well. I accidentally deleted all my emails back & forth with him, but I know it was more than just polishing and detailing (although he was certainly doing that as well) - I just don't remember enough details to speak to it...
Less mass and the crank will flex less, esp with only 3 mains....no ? It would also be easier on bearings with less mass to support? Rat
Yeah Ive seen that page...some great info there. Surely someone here has whittled away on one of Henry's finest? Bruce? AV8 ? Flatjack ? Anyone? Rat
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