Refresh951's Hybrid Ultra Stroker Build
#1801
Addict
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That has to be the luckiest outcome for failure of this proportion. Hope you make it even better this time.
#1802
Drifting
Years ago I knew a guy that worked at a successful race engine shop that mainly did 4 cylinder engines. They weren't keen on grinding cranks 1st undersize, and usually advised a new crank budget permitting. OK these stroker engines aren't revving to 8k + and probably only spend seconds over 6k, but grinding that much off and then the force required to cold straighten isn't as good as an option as an original 3.0 crank IMO.
#1804
Drifting
There is a shop in Redding California that rebuilds harmonic dampeners. I believe the cost is around $250. It's pricey but so is everything else on a built 951. IMO it's worth it. http://damperdoctor.com/index.php?ro...mation/contact
#1805
Rennlist Member
Thread Starter
Out of curiosity, do you run a non spring damped clutch disc..?
And solid engine mounts..?
On track, short of natural backlash in CVs and transmission gearing, only the length of the long input between the clutch spline and the transmission input shaft coupler absorb torsional forces through the drivetrain when you remove the spring center from the disc and the isolator (rubber mounts) that both absorb torsional forces when you hop the rear tires on an errant or missed rev matched downshift with high grip tires.
BTW - re your video, it's hard to do with traffic, but in a car with your power, after out lap, try making some laps in 5th gear only...., never downshift.
This will teach you momentum faster than anything else.T
And solid engine mounts..?
On track, short of natural backlash in CVs and transmission gearing, only the length of the long input between the clutch spline and the transmission input shaft coupler absorb torsional forces through the drivetrain when you remove the spring center from the disc and the isolator (rubber mounts) that both absorb torsional forces when you hop the rear tires on an errant or missed rev matched downshift with high grip tires.
BTW - re your video, it's hard to do with traffic, but in a car with your power, after out lap, try making some laps in 5th gear only...., never downshift.
This will teach you momentum faster than anything else.T
Thanks for the input on my driving. I will give that a try. I have improved quite a bit since any posted videos
looking at the metal grain patterns in that photo that looks like a crack->snap caused by crank whip rather than torsional stress.
probably could've used a revised (heavier?) harmonic damper along with the larger radiuses as mentioned.
if it were torsional failure...easiest to picture a splined driveshaft twisted from mega torque input, the metal twists on itself as if it were a a towel being wringed out, if smaller scale.
probably could've used a revised (heavier?) harmonic damper along with the larger radiuses as mentioned.
if it were torsional failure...easiest to picture a splined driveshaft twisted from mega torque input, the metal twists on itself as if it were a a towel being wringed out, if smaller scale.
There is a shop in Redding California that rebuilds harmonic dampeners. I believe the cost is around $250. It's pricey but so is everything else on a built 951. IMO it's worth it. http://damperdoctor.com/index.php?ro...mation/contact
#1806
Rennlist Member
Thread Starter
Another consideration - When you take the crank out to maximum stroke, you really cannot optimize the fillet radius. The more I look at the 94.7mm stroke, the more I think it is better to back off a bit. This pics shows what could have been if there was enough material. Rebuild will be 92 mm stroke with optimized fillets and nitriding.
#1807
Rainman
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2? years ago i was gauging interest for having custom billet cranks made, i think Molnar was OK with 94mm (will double check), something around $1500/pc with 5 pc minimum.
i think he wanted a larger rod pin though.
surely the necessary fillets could be built-in at that point.
i think he wanted a larger rod pin though.
surely the necessary fillets could be built-in at that point.
#1808
Rennlist Member
Thread Starter
Reusing my block, had to overbore the sleeves 0.010" out to 4.040". Quite a bit of wear in the bores, on the order of 0.003" to 0.004". The rod ratio on the 95 mm stroke is 1.58 and it is a factor in terms of wear. Something to consider as you go higher in stroke. Got about 10K miles and a lot of track events. Rebuild is coming along, just need my 92 mm crank and then it can go back together. Hopefully have the crank in 3 weeks.
#1809
Drifting
Join Date: Aug 2009
Location: Bangkok, Thailand, Milpitas, CA & Weeki Wachee, FL
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I doubt many if any besides Emanuel and I would be interested but I will have a quote in a few days from Marine Crankshaft on a full Billet Hybrid Stroker crank at 94mm. Their work is phenomenal even by my standards.
#1810
Rainman
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2? years ago i was gauging interest for having custom billet cranks made, i think Molnar was OK with 94mm (will double check), something around $1500/pc with 5 pc minimum.
i think he wanted a larger rod pin though.
surely the necessary fillets could be built-in at that point.
i think he wanted a larger rod pin though.
surely the necessary fillets could be built-in at that point.
#1812
Race Car
#1813
Rainman
Rennlist Member
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hope your cranks don't come from your cam gear guy.
molnar billets are mfrd in China and then finish machined to spec in USA just like pretty much any other brand of cranks/rods, with few exceptions.
#1815
Addict
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Let me see if I get this right.. Crank breaks in two pieces trough the journal and solution to that is crank with big holes trough journals. Hmmm.