Quote:
Originally Posted by Half-Inch Stud
Sorry for my cynicism, but Post 43 might have been ARP TQ-level induced failure. Agreed on the Damper culprit.
Custom 2-stroke unmanned aircraft engine busted the crank we made, during FAA endurance life testing. Professional metallurgy analysis showed the "SAE" 4340 steel billet (China!) has magnesium sulfide striations, that lead to early fatigue. Know thy Billet source !!
Factory PMD Cranks sound real good to me.
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Interesting that you bring up Billet source. Tom V always makes a big deal out of material for crankshafts being real "Timken ball bearing steel" There is something to that for sure. The mention of the Crower Billet crankshaft breaking may have some tie in there. For a couple years, Crower broke with tradition and bought a quantity of Chinese billets. They made a good size run of Pontiac billet Pontiac cranks from this stock. To their credit, they sold these cranks for about half the price of their domestic sourced billet cranks. We bought 3 of them and had no issues in the nitro engine with them. But you just never know. Of the 100's of things to worry about in an engine that can fail, a broken crankshaft would still be pretty low on the worry list. A good harmonic balancer with a press fit to the crank nose, a premium bolt with 200 ft. Lbs + torque is a must on a performance engine. My balancer of choice for a serious engine build is ATI.