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beetleseb
Samba Member
Joined: November 09, 2006
Posts: 430
Location: Cheltenham UK
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 Posted: Thu Feb 04, 2016 4:00 am Post subject: Crankshaft |
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Hi guys
Looking at having a crankshaft built at DPR
Just wondering if anyone as suggestions for both stroke and counterweights
I can choose either 69 or 72 and obviously with or without counterweights.
I've got an aluminium 49 case, a Mr okrassa Porsche cam, 77mm B and P, I'll be running twin carbs and fairly stock heads with slightly bigger valves.
Ideally I'd like to use stock con rods unless there's a tried and tested alternative. Especially as I have some good rebuilt ones.
Engine won't be driven too hard just normal driving probably wont see 4000rpm very often!
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txoval
Samba Member
Joined: January 23, 2004
Posts: 3552
Location: The Woodlands, TX
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| Posted: Thu Feb 04, 2016 7:06 pm Post subject: Re: crankshaft |
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I'd recommend a 69mm stroke. DPR is great to deal with and their products are even better
I prefer a counterweighted crank with a lightened flywheel (DPR can provide both, as well as your clutch assembly). If you buy all the parts from DPR they'll balance them for you, which is key to having a smooth running engine.
I would also say a counterweight crank is not necessary, but my preference |
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beetleseb
Samba Member
Joined: November 09, 2006
Posts: 430
Location: Cheltenham UK
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| Posted: Fri Feb 05, 2016 5:26 am Post subject: Re: Crankshaft |
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Cheers
Do the stock rods and pistons work with 72mm? I'm leaning towards bigger at the moment
Seb
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jays58s
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Joined: August 23, 2004
Posts: 2133
Location: Nor-Cal
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| Posted: Fri Feb 05, 2016 11:29 am Post subject: Re: Crankshaft |
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| beetleseb wrote: |
Cheers
Do the stock rods and pistons work with 72mm? I'm leaning towards bigger at the moment
Seb |
You can run the stock rods and pistons if you get a crank with 36hp sized journals, you just have to shim it a little more. Depending on the crank, you can either run stock Vw rod, or Porsche 356 rods like I have in my engine. I have a freshly reground 72mm crank I'm not using either if you're interested. I'm not trying to make this a for sale ad, just thought I'd help you out and you wouldn't have to wait to have one made. |
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RichardinNZ
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Joined: September 16, 2011
Posts: 280
Location: Auckland, New Zealand
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beetleseb
Samba Member
Joined: November 09, 2006
Posts: 430
Location: Cheltenham UK
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| Posted: Sat Feb 06, 2016 2:45 am Post subject: Re: Crankshaft |
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Nothing stops a crank breaking if its abused. The 50mm journals are an inherent weak spot, thats why they were enlarged. But Ive often been told that the forged og vw cranks are the strongest. That along with dprs reputation is what prompted me to choose his over ww. The fact that you have such options to choose from is merely a bonus.
Theres not much in it. A cw 69mm or 72mm from dpr is $550. take off the counterweights and exchange a crank and its cheaper still
I just want to make sure I get the best for this build. at the moment that looks like a non cw 72mm. I would have loved to get it done here in the UK but suppliers are talking aout £1000 thats $1450..........
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tobiasax
Samba Member
Joined: May 07, 2004
Posts: 202
Location: Sweden
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| Posted: Sat Feb 06, 2016 5:08 am Post subject: Re: Crankshaft |
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| beetleseb wrote: |
Cheers
Do the stock rods and pistons work with 72mm? I'm leaning towards bigger at the moment
Seb |
Stock (as in VW original from the 50's) pistons need to be machined somewhat to clear the crank even for 69 mm stroke.
One thing to observe is that there are a reinforcement web on the inside of the stock piston. With the 69,5 mm WW crank you can leave it un-touched (but it's not a big margin). Without the re-inforcement web I am afraid the piston might become to weak and lose it's shape.
The 72 mm crank goes 1,5 mm deeper and I don't know if you can get clearance without removing the web. Perhaps some one here has first hand experience?
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beetleseb
Samba Member
Joined: November 09, 2006
Posts: 430
Location: Cheltenham UK
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| Posted: Sat Feb 06, 2016 5:50 am Post subject: Re: Crankshaft |
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| tobiasax wrote: |
| beetleseb wrote: |
Cheers
Do the stock rods and pistons work with 72mm? I'm leaning towards bigger at the moment
Seb |
Stock (as in VW original from the 50's) pistons need to be machined somewhat to clear the crank even for 69 mm stroke.
One thing to observe is that there are a reinforcement web on the inside of the stock piston. With the 69,5 mm WW crank you can leave it un-touched (but it's not a big margin). Without the re-inforcement web I am afraid the piston might become to weak and lose it's shape.
The 72 mm crank goes 1,5 mm deeper and I don't know if you can get clearance without removing the web. Perhaps some one here has first hand experience? |
I have some mahle flat top pistons and some 40hp pistons too so maybe these will be an easier fit. Theres only one way to find out!!
My main issue is shipping at the moment. That buys me some time to make up my mind on the stroke
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