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Refresh951's Hybrid Ultra Stroker Build

 
Old 04-06-2018, 05:55 AM
  #1801  
Voith
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That has to be the luckiest outcome for failure of this proportion. Hope you make it even better this time.
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Old 04-06-2018, 06:01 AM
  #1802  
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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.
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Old 04-06-2018, 12:31 PM
  #1803  
V2Rocket
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^^ crank cold-straightening machines are serious business
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Old 04-06-2018, 01:30 PM
  #1804  
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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
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Old 04-07-2018, 06:33 PM
  #1805  
refresh951
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Originally Posted by Tom M'Guinn View Post
If you get a new motor in by June, after I've been sitting on my next-gen motor parts for way too long, I might actually be shamed into action...
If all parts come in as expected it will be done

Originally Posted by 951and944S View Post
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
Spec hybrid clutch, does have springs, LR semi Solid mounts. This is definitely not a torsional failure.

Thanks for the input on my driving. I will give that a try. I have improved quite a bit since any posted videos

Originally Posted by V2Rocket View Post
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.
I think this is just simply a load failure. I do not believe the harmonic balancer played any major role.

Originally Posted by Voith View Post
That has to be the luckiest outcome for failure of this proportion. Hope you make it even better this time.
God helped me on this one

Originally Posted by Humboldtgrin View Post
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
Interesting. Thanks for the link.
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Old 04-07-2018, 06:35 PM
  #1806  
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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.

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Old 04-08-2018, 11:37 AM
  #1807  
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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.
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Old 04-17-2018, 06:10 PM
  #1808  
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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.
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Old 04-17-2018, 11:51 PM
  #1809  
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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.
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Old 04-18-2018, 05:20 AM
  #1810  
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Originally Posted by URG8RB8 View Post
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.
Originally Posted by V2Rocket View Post
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.
😑.
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Old 04-18-2018, 09:57 PM
  #1811  
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Slightly better than Molnar. I too looked into that. There is a reason they are so cheap.
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Old 04-18-2018, 10:26 PM
  #1812  
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Originally Posted by URG8RB8 View Post
Slightly better than Molnar. I too looked into that. There is a reason they are so cheap.
And the reason being...?

Are you referring to the pass through at the rod journals..?

A lot of late cranks have this feature.

T
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Old 04-18-2018, 11:42 PM
  #1813  
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Originally Posted by URG8RB8 View Post
Slightly better than Molnar. I too looked into that. There is a reason they are so cheap.
price =/= quality.

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.
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Old 04-19-2018, 02:27 AM
  #1814  
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The exception would be Thor?
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Old 04-19-2018, 05:18 AM
  #1815  
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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.
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