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esde
Samba Member
Joined: October 20, 2007
Posts: 5971
Location: central rust belt
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 Posted: Tue Dec 05, 2023 6:29 am Post subject: drilling a 36hp crank and flywheel for 8 dowels |
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I have a stock 36hp crank which I would like to convert to 8 dowels. My understanding is that the 8 dowel pattern used on 356 Porsche is the upgrade. I'm looking all over for a drill jig for this pattern but not finding anything, does one exist and could anyone provide a link? The ones for the later 8mm dowel pattern are plentiful but will not work
If needed I may use a 356 flywheel to make my own jig, but I'd rather just buy the jig and spend my time elsewhere..
Many thanks. SD
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56samba
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Joined: June 25, 2015
Posts: 262
Location: Germany
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| Posted: Wed Dec 06, 2023 1:49 am Post subject: Re: drilling a 36hp crank and flywheel for 8 dowels |
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I was in the same situation recently during the restoration of my Okrasa engine and couldn't find a drill jig.
Using a 356 flywheel as a jig worked surprisingly well. Subsequent reaming of the holes is recommended. |
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Robert Chambers
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Joined: August 11, 2005
Posts: 216
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| Posted: Wed Dec 06, 2023 10:07 am Post subject: Re: drilling a 36hp crank and flywheel for 8 dowels |
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How about using a 356 or 912 metal flywheel gasket as a pattern?
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esde
Samba Member
Joined: October 20, 2007
Posts: 5971
Location: central rust belt
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| Posted: Wed Dec 06, 2023 3:54 pm Post subject: Re: drilling a 36hp crank and flywheel for 8 dowels |
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| Robert Chambers wrote: |
| How about using a 356 or 912 metal flywheel gasket as a pattern? |
Probably not as accurate/ easy as I would like. It's a lot more work to find the center of a hole in the gasket than the actual flywheel. I may use a flywheel, and get some 6mmx8mm bushings. This way I can drill through the flywheel with a 6mm pilot. Then remove the flywheel and bushings, drill to the final size and ream.
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Robert Chambers
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Joined: August 11, 2005
Posts: 216
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| Posted: Wed Dec 06, 2023 5:27 pm Post subject: Re: drilling a 36hp crank and flywheel for 8 dowels |
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I have the flywheel. You can use it if needed. I plan to do the same thing to my crankshaft.
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IN2VWS
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Joined: January 29, 2006
Posts: 2521
Location: Australia
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| Posted: Sun Mar 03, 2024 12:18 am Post subject: Re: drilling a 36hp crank and flywheel for 8 dowels |
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TomSimon
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Joined: January 13, 2004
Posts: 751
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| Posted: Sun Mar 03, 2024 2:24 am Post subject: Re: drilling a 36hp crank and flywheel for 8 dowels |
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Very nice! Replaceable hardened drill bushings, a piece of professional tooling. And that patina!
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esde
Samba Member
Joined: October 20, 2007
Posts: 5971
Location: central rust belt
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| Posted: Sun Mar 03, 2024 4:46 pm Post subject: Re: drilling a 36hp crank and flywheel for 8 dowels |
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Amazing.
So, it has a VW number. Did any VW have an 8 dowel crankshaft from the factory? I'm wondering what the factory made the tool for?
Is one of the pins offset? Maybe it was to repair a crankshaft that had damaged holes?
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RolandD
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Braukuche
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Joined: September 03, 2004
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| Posted: Tue Mar 05, 2024 8:59 am Post subject: Re: drilling a 36hp crank and flywheel for 8 dowels |
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There’s no need to eight dowl it unless you are building an engine capable of running the same high RPMs as a Porsche 356. In that case why wouldn’t you buy a 69.5 stroker crank that’s already eight dowled?
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esde
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Joined: October 20, 2007
Posts: 5971
Location: central rust belt
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| Posted: Tue Mar 05, 2024 3:03 pm Post subject: Re: drilling a 36hp crank and flywheel for 8 dowels |
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| Braukuche wrote: |
| There’s no need to eight dowl it unless you are building an engine capable of running the same high RPMs as a Porsche 356. In that case why wouldn’t you buy a 69.5 stroker crank that’s already eight dowled? |
That's not really accurate.
Drag race starts and hard shift are what usually oval out the dowel holes, but cars that are driven hard are well known to do it also. Especially. cars that are driven with a lot of downshifting/ compression braking. The 4 little 6mm pins are barely adequate for 36hp.
Of course at hight rpm, there is more mass (30lbs of flywheel and clutch assembly!) and that inertia is more likely to kill the pins, but it does happen even on stock street driven cars.
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Iowa Mark
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Joined: May 06, 2004
Posts: 1071
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| Posted: Tue Mar 05, 2024 5:48 pm Post subject: Re: drilling a 36hp crank and flywheel for 8 dowels |
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| esde wrote: |
| Braukuche wrote: |
| There’s no need to eight dowl it unless you are building an engine capable of running the same high RPMs as a Porsche 356. In that case why wouldn’t you buy a 69.5 stroker crank that’s already eight dowled? |
That's not really accurate.
Drag race starts and hard shift are what usually oval out the dowel holes, but cars that are driven hard are well known to do it also. Especially. cars that are driven with a lot of downshifting/ compression braking. The 4 little 6mm pins are barely adequate for 36hp.
Of course at hight rpm, there is more mass (30lbs of flywheel and clutch assembly!) and that inertia is more likely to kill the pins, but it does happen even on stock street driven cars. |
I have to agree. Way back in 1968 my 1957 stock bug spun the flywheel. I was just your typical teen-age boy driving up and down Grand Ave on a friday night. No, honestly! |
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RWK
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| Posted: Wed Mar 06, 2024 7:41 am Post subject: Re: drilling a 36hp crank and flywheel for 8 dowels |
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Could you drill the 4-6mm pins to 8mm? PM me, I could possibly build a drill jig, do you know the bolt circle, or radius from center, or pin center to center?
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esde
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Joined: October 20, 2007
Posts: 5971
Location: central rust belt
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| Posted: Mon Mar 11, 2024 5:50 am Post subject: Re: drilling a 36hp crank and flywheel for 8 dowels |
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| RWK wrote: |
| Could you drill the 4-6mm pins to 8mm? PM me, I could possibly build a drill jig, do you know the bolt circle, or radius from center, or pin center to center? |
To jump from 6 to 8mm, there would be .5mm between the dowels and the inside/ outside edges of the crankshaft, probably not enough material. To oversize the existing pins, you could use 1/4" (6.32mm), 7mm, or 9/32 (7.14mm)
I have started to make a jig, based on the pattern that DPR uses. If it works well, I will share the details.
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RolandD
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Joined: January 15, 2017
Posts: 247
Location: Menomonee Falls, Wis
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| Posted: Mon Mar 11, 2024 6:09 pm Post subject: Re: drilling a 36hp crank and flywheel for 8 dowels |
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Please do share the geometry details.
Roland |
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