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ARP flywheel bolts

 
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gegge  



Joined: 27 Jul 2007
Posts: 1075
Location: Sweden

PostPosted: Fri Oct 05, 2012 10:17 pm    Post subject: ARP flywheel bolts Reply with quote

I didnīt want to reuse the 30 year old stock flywheel bolts and expected to pay a lot when buying new ones from Porsche. It wasnīt easy finding short M12 x 1.5 with a shallow head in the hardwarestore either. Especially if you want grade 10.9 or better. Remember that flywheel bolts are different from ordinary bolts and the stress is severe.

Finally I noticed that BMW (E30) M3 with the S14 EVO engine with single mass flywheel used bolts that are very similiar to ours: HEX BOLT M12X1,5X22 11220616143 $2.01

Even better, ARP does provide a kit of 8 pcs in their Pro Series, originally developed for NASCAR competition and has a 200,000 psi rating. #201-2801 for some $50
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Carl Fredrik Torkildsen

924 turbo -81 Carrera GT RESTOMOD
924 turbo -80 Dolomite De Luxe
924 -85 DP kit, BBS RS, M030 and tuned engine
924s -86 Black on black turbo with Fuchs
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peterld  



Joined: 10 Dec 2006
Posts: 771
Location: Noosa Heads QLD Australia

PostPosted: Sat Oct 06, 2012 9:33 pm    Post subject: Reply with quote

Great find Gegge!
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ideola  



Joined: 01 Oct 2004
Posts: 15501
Location: Woodstock IL

PostPosted: Tue Feb 12, 2013 1:10 am    Post subject: Reply with quote

I just installed a set of these on the Club Sport motor and I can confirm that they work perfectly. I also measured the early S2 flywheel (which is what I installed on the club sport), the S1 flywheel, and the NA flywheel with washer, as well as the depth of the blind holes in the end of the crank.

These ARP bolts are 22mm long and have a 8mm unthreaded shank. The heads of these bolts are about 1mm shallower than the stock bolts, so not concern about interfering with the clutch disc either.

All of the flywheels I measured had 9mm or longer depth where the bolt passes through; the blind holes in the crank are ~18mm; so from my measurements and test fitting, it appears that these bolts should work for ALL of the 924 applications. The only one I can't confirm for certain is the late S2 931 flywheel with the rubber damped clutch disc because I don't have one of those flywheels on hand. However, looking in PET, it indicates that those bolts are 18mm long, which is only 4mm shorter than these bolts, and there should be plenty of depth in the crankshaft blind holes to accept the additional length.

I will be adding these to my site later this week
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88 924S SE | 82 931 Holbert | 81 Euro 931 | 81 Weissach | 80 US 928 | 80 US 931 '941' | 78 D-Prod Replica | 78 w/D-Prod kit | 78 Poli-Form | 78 Limited Edition
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gegge  



Joined: 27 Jul 2007
Posts: 1075
Location: Sweden

PostPosted: Wed Oct 16, 2013 5:24 pm    Post subject: Reply with quote

There seems to be another ref for OEM BMW M12x1,5x25 in 12.9 quality: 244238930

A picture of OEM 10.9, BMW 12.9 and ARP Pro:

I
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Carl Fredrik Torkildsen

924 turbo -81 Carrera GT RESTOMOD
924 turbo -80 Dolomite De Luxe
924 -85 DP kit, BBS RS, M030 and tuned engine
924s -86 Black on black turbo with Fuchs
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