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Crankshaft

 
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motormouth  



Joined: 28 Feb 2010
Posts: 113
Location: Canton

PostPosted: Wed Aug 08, 2018 5:56 am    Post subject: Crankshaft Reply with quote

Does anyone have a good crankshaft for sale/trade? Standard bearings required, no reground cranks. I am after one at the moment.
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Fifty50Plus  



Joined: 28 Feb 2008
Posts: 1006
Location: Washington DC area

PostPosted: Wed Aug 08, 2018 7:01 am    Post subject: Reply with quote

For which engine?
_________________
1979 924 NA race car
1982 924 NA race car - Sold
1982 924 Turbo almost a PoS
1981 924 Turbo a real PoS, new engine
1982 924 Turbo nice body, blown engine
1972 911 E race car - going to Vintage
Various 944s to become IT-S race car
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motormouth  



Joined: 28 Feb 2010
Posts: 113
Location: Canton

PostPosted: Wed Aug 08, 2018 8:23 am    Post subject: Reply with quote

Sorry for not clarifying lol. 924 turbo. My understanding is that all 2.0 liters have the same one? No difference between turbo and NA?
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Fifty50Plus  



Joined: 28 Feb 2008
Posts: 1006
Location: Washington DC area

PostPosted: Wed Aug 08, 2018 9:33 am    Post subject: Reply with quote

There is a difference. The input shaft bearing is a different size between the two engines and rides in a different place (flywheel vs crank as I recall). All main and rod bearings and throws are the same between the two cranks.
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1979 924 NA race car
1982 924 NA race car - Sold
1982 924 Turbo almost a PoS
1981 924 Turbo a real PoS, new engine
1982 924 Turbo nice body, blown engine
1972 911 E race car - going to Vintage
Various 944s to become IT-S race car
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motormouth  



Joined: 28 Feb 2010
Posts: 113
Location: Canton

PostPosted: Wed Aug 08, 2018 12:11 pm    Post subject: Reply with quote

What is the reason for the difference? Is the 931 crank supposed to be stronger?
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Ian89C4  



Joined: 01 Apr 2011
Posts: 534
Location: North Carolina

PostPosted: Wed Aug 08, 2018 12:33 pm    Post subject: Reply with quote

931 input bearing rides on the flywheel...due to the clutch difference between the turbo and NA (hydraulic vs. cable).

No difference in strength.

I think the flywheel end of the turbo crank is also different as a whole, I would have to check, but I think it is a different thickness due to completely different flywheel.
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Ian Edgerly
Spiveys Corner, North Carolina

Current:
1981 924 Weissach Race Car ("Serenity")
1980ish 931 ("Alice")
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motormouth  



Joined: 28 Feb 2010
Posts: 113
Location: Canton

PostPosted: Wed Aug 08, 2018 12:37 pm    Post subject: Reply with quote

Ok that makes sense. I guess Iím after an NA crank then. It was a turbo shortblock that is going into an NA. I am trying to build one of these high compression hybrids with turbo pistons and an NA head. I have s2 pistons, but need a crank.
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MikeJinCO  



Joined: 08 Jun 2010
Posts: 731
Location: Maysville, Colorado

PostPosted: Wed Aug 08, 2018 3:49 pm    Post subject: Reply with quote

My version is very close to being done. It has S2 pistons with a complete turbo block/crank/rods and a NA flywheel bolted on. The pilot bearing fit properly. I would get the Total Seal rings rather than have the pistons re-grooved for standard rings although you better check the ring lands for wear as I heard of some other(non 924) applications having some problems with Total Seal. Just be very careful. On my block the pistons came out flush to the top of the block and I'm using a .40 Cometic head gasket. The pistons did need cutting for valve reliefs due to the pistons chasing the valves on overlap. That added about 6cc to the combustion chamber. Actual CR is about 10.2. I'll run either non-ethanol premium or AV gas. Weber carbs don't really like the ethanol when they sit around not running for a month or two, which this motor will do as the car is no where close to street legal-it does have brake lights.

Doing it again I would just go get some new JE or Diamond Pistons. By the time you get rings and cut the valve clearance in the pistons you are about 2/3ds of the way to a new, lighter and much stronger pistons-- with rings and pins. Balancing around here is $150-$200 and should be done anyway. Get pin bushings from EBS Racing, they are a standard Crower part that gets shortened a bit and needs fitted to the individual pin anyway.

I am currently waiting for my head as the machinist who cut down the valve spring bases for us for my non standard springs was way behind on some of his production work .
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Mike
Poco a Poco, '80 future track car
'77 924
cricketdesigns.com
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MikeJinCO  



Joined: 08 Jun 2010
Posts: 731
Location: Maysville, Colorado

PostPosted: Wed Aug 08, 2018 11:51 pm    Post subject: Reply with quote

Sorry, It was late last night, this shouldn't have been put there. I don't believe the crank is any different. My pilot bearing, NA flywheel, clutch, bellhousing arrangement all fit perfectly in the 931 crank. Also my other car has a reground crank and with the Chinese bearings available it is running quite well so I wouldn't be scared of an undersize crank.
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Mike
Poco a Poco, '80 future track car
'77 924
cricketdesigns.com
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motormouth  



Joined: 28 Feb 2010
Posts: 113
Location: Canton

PostPosted: Thu Aug 09, 2018 1:03 am    Post subject: Reply with quote

Well, the reason I am after a non-undersize crank is that I have some NOS mains I picked up on ebay for cheap. I was hoping to utilize those instead of ordering new parts.

Looking at the technical parts manual, it looks like both the 924 and 924 turbo get crank 046 105 021 A. Unless I am misreading it, are the cranks the same in both cars?
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Fifty50Plus  



Joined: 28 Feb 2008
Posts: 1006
Location: Washington DC area

PostPosted: Thu Aug 09, 2018 4:58 am    Post subject: Reply with quote

Check the part number on the bearings carefully. early '77 cranks had a different sized bearing than all the later NA and turbo cranks. That may be why they were cheap. The later bearings have been NLA for years until folks on this board had new ones manufactured.
_________________
1979 924 NA race car
1982 924 NA race car - Sold
1982 924 Turbo almost a PoS
1981 924 Turbo a real PoS, new engine
1982 924 Turbo nice body, blown engine
1972 911 E race car - going to Vintage
Various 944s to become IT-S race car
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Ian89C4  



Joined: 01 Apr 2011
Posts: 534
Location: North Carolina

PostPosted: Thu Aug 09, 2018 9:43 am    Post subject: Reply with quote

The cranks are the same, but the na had a input shaft bearing carier that you will need with the na flywheel. They are not sold as separate part numbers. As a note you cannot use a 931 flywheel on the na cars, the clutch mechanism is different on the two versions.
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Ian Edgerly
Spiveys Corner, North Carolina

Current:
1981 924 Weissach Race Car ("Serenity")
1980ish 931 ("Alice")
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MikeJinCO  



Joined: 08 Jun 2010
Posts: 731
Location: Maysville, Colorado

PostPosted: Sun Aug 12, 2018 12:01 am    Post subject: Reply with quote

I did buy that part, got it from Sunset Porsche I believe, so probably still available.
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Mike
Poco a Poco, '80 future track car
'77 924
cricketdesigns.com
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Ian89C4  



Joined: 01 Apr 2011
Posts: 534
Location: North Carolina

PostPosted: Sun Aug 12, 2018 8:15 am    Post subject: Reply with quote

Very cool! Then a turbo crank will work. Just don't swap flywheels.

Good luck!

Cheers
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Ian Edgerly
Spiveys Corner, North Carolina

Current:
1981 924 Weissach Race Car ("Serenity")
1980ish 931 ("Alice")
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Britain  



Joined: 26 Nov 2013
Posts: 105
Location: Hillsboro, OR

PostPosted: Fri Aug 24, 2018 4:59 am    Post subject: Reply with quote

I have a couple of crankshafts and some other related engine parts still available.

They are listed here:

http://forums.pelicanparts.com/porsche-924-944-968-used-parts-sale-wanted/979283-huge-assortment-931-engine-parts.html



-Britain
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