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Alstrup Samba Member
Joined: July 12, 2007 Posts: 7216 Location: Videbaek Denmark
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Posted: Sun Sep 27, 2020 10:50 am Post subject: Re: Max hp 4 dowel crank flywheel |
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A couple of things.
A turbo engine is not nearly as hard on the gland nut as a similar HP N/A engine is. Once "things are rolling" it can handle incredible amounts of power if assembelled correct.
I´m not saying that a stock gland nut can´t hold more than 80 hp. I´m saying that from thereon up you are in grey country. I´m sure that a Scat/CB or what ever quality 38 mm bolt along with a larger washer will improve holding power a good deal. How much I do not know. Berg senior tried it out some, but I don´t think he ever published anything about his findings. My guess is that it was is because the gains were minimal. I could be wrong though.
Also, back when beetles were used for rally the engines typically pulled about 125 hp. And since it was not legal to remove anything from the crankshaft they had to use higher torque on the stock 4 dowels. - USUALLY - they held together, but every once in a while a bolt let go and the flywheel & crank was destroyed. Again, these engines were not so hard on the parts in the starts, because it was often on gravel and the engines only had 150ish Nm torque and again, once they were rolling it wasnt so bad.
The term "We did that 30 years ago. It worked well" doesnt hold in a lot of situations. In this case I will also say, barely. Reason is, that today we build engines which produce A LOT more usable torque than what was built at an average back then. And it is the torque that kills it, not the hp. - Well, if you get enough hp it will, but you´ll catch the drift.
Last. The surface versus torque is progressively proportional, so 8 properly installed dowels can hold about 200% more than 4 stock dowels torquewise. In a shock load I am not sure what the factor is, but it is at least 100% (I´m sure there is an engineer who knows this or can dig up the numbers) _________________ https://www.thesamba.com/vw/forum/viewtopic.php?t=435993 |
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buguy Samba Member
Joined: November 17, 2003 Posts: 4915 Location: Port Orange, FL
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Posted: Sun Sep 27, 2020 11:31 am Post subject: Re: Max hp 4 dowel crank flywheel |
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I agree. My turbo engine didn't make much power right off the line. I never tried building boost on the 2 step before launching. I still had the stock 4.37 trans so first gear was almost unusable so i just rolled through first and then once i was in second i would let it rip. So i never did shock it. |
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c77owen Samba Member
Joined: July 07, 2017 Posts: 454 Location: Kansas City, MO
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Posted: Mon Sep 28, 2020 12:58 pm Post subject: Re: Max hp 4 dowel crank flywheel |
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modok wrote: |
Tight dowel pins are better than loose ones.
Steel flywheels are stronger than cast iron
Some gland nuts are better than others, lube and head size needs to be considered to get the right torque.
The crank being tightly spigoted into the flywheel register strengthens the whole thing.
You don't have to do everything right, but you have to do enough right. |
This is dead on. Especially about being tightly spigoted. I received a poor (not tight) fitting flywheel for a customer's engine....returned it to get one that fit the dowels and crank better....went through 5 flywheels before we found one that was machined properly with the right fit and it was an 8 dowel. If you have ever had one shear the dowels or just simply come loose, you will know it is worth the effort to find the right fit the first time |
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Ohio Tom Samba Member
Joined: February 09, 2006 Posts: 1660 Location: Marshallville Ohio
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Posted: Mon Sep 28, 2020 1:11 pm Post subject: Re: Max hp 4 dowel crank flywheel |
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I have stripped a few stock gland nuts with over-torque.
Never, not once seen a Chromloy one fail.
Stock gland nuts will rip the threads off.
If you ever remove one and the threads are sharp enough to cut you?
It's about to fail....
It's a sad sight to see someone build a nice race motor with 8-dowel crank. Only to use a stock gland nut that fails.
Yes, adding a chromoly gland nut to a stock 4 dowel crank is an upgrade.
Very common to do the same to Porsche 356 engines.
It's about the only part that's OK to use "non stock" on a 356 restoration.
Even the Anal guys are OK with gland nut upgrades... |
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scfwb Samba Member
Joined: April 17, 2013 Posts: 6 Location: NC Coast
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Posted: Sat Nov 07, 2020 8:47 am Post subject: Re: Max hp 4 dowel crank flywheel |
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Might be a bit off topic but since you guys seem to know more about this... I thought I would ask - I have a 1915 engine with 8 dowel crank and lightened flywheel (bought this from a friend as a complete engine). Since I'm putting this in a bus I thought that I would prefer a full weight (stock) flywheel. Question is - do I have to drill/ream the stock flywheel for the 8 dowels or can I just use it with 4 dowels with he 8 dowel crank? Thx in advance |
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chrisflstf Samba Member
Joined: February 10, 2004 Posts: 3442 Location: San Diego
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Posted: Sat Nov 07, 2020 2:31 pm Post subject: Re: Max hp 4 dowel crank flywheel |
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8 is better, but 4 will work. I would use a chromemoly hd nut and washer. If you go with 4, you will need to remove 4 dowels from the crank if installed. That may not be easy |
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