Another question for you!
Ok, which crankshaft do you currently run in your K’s for high engine speeds, the sort of speeds I have in mind is 8.5K
K series VHPD
Standard crank but counter balanced
QED’s (Farndon) crank??
Or am I way off the mark here?
I should also add, the reason I ask is that i’m in the process of trying to spec a suitable crank for my engine.
Cheers in advance!!!
I have a Doug Kiddie Engineering crank in my racer. It’s been doing endurance and sprint races since 2000 revving to 8500-9000. It’s just about the only component that hasn’t been changed in all that time!
If you are considering a steel crank then the DKE crank has a lot to recommend it, not least a decent counterweight on the crank and hollowed big-end journals which significantly recuces secondary OOB forces. The counterweights are also massive enough to take HMI.
mmmm DK engineering cranks…perhaps when i win the lottery!
So, what is the minimum crank spec for a K revving to 8500rpm? Would the standard crank with counter weights and a full engine balance suffice for an engine that will only see the odd track day and mainly used for the road ? Or is this a time bomb down to fatigue?
Given that Steve Butts and Dave Skeggs have both been running standard K cranks in their engines fully balanced and Tungsten inserted without issue then I’d say you don’t need to go too extreme with the crank so long as you fork out to have it tungsten inserted and balanced.
The Tungsten insertion and balancing does cost almost as much as a DKE crank on its own though, so it’s not cheap, but as Dave said I’d still want to go through the same balancing/insertion process on a DKE crank anyway (meaning about 3250 pounds just on the crankshaft!).
Given that traditionally the crankshaft doesn’t seem to be a major weak point of the engine and the crank problems there have been are more symptomatic of fatigue from poor balance causing the crank to bend at high RPM, then I’d imagine a standard crank prepared properly will do just fine.
This is the combo I’m going for with my engine as the jury seems to be out on steel cranks as they’re not a panacea… Given the long stroke of the engine, anything you can do to reduce load on the crank is good hence lighter (steel) rods are probably a good way to go.
Thanks so much for the info; thats what I was hoping to hear about properly sorting the standard crank, my engine spec is finally coming together now.
Hopefully in the new year I’ll be paying Steve Smith a visit.
Thanks once again everyone!