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bcrazy Samba Member
Joined: October 24, 2009 Posts: 231 Location: Oslo
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Posted: Wed Nov 18, 2020 2:28 pm Post subject: Likelyhood of breaking a 64 mm crank |
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Did a search and found som examples of broken 64 mm cranks.
Question is how common is this?
If i were to upgrade my 63 1200 with 83 mm cylinders, 1300 heads, dual 32 PDSIT carbs and a better flowing exhaust
Should i worry about the crank breaking? |
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[email protected] Samba Member
Joined: June 24, 2015 Posts: 718 Location: Rialto. CA
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Posted: Wed Nov 18, 2020 5:40 pm Post subject: Re: Likelyhood of breaking a 64 mm crank |
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You should be fine no problem ..the only 64mm crank i would be worry about was the early 36hp/40hp 1959-60 "bastard" crankshaft those cranks were cast and would break ... but i doubt you have a cast crank since yours is a 63 ..if your worried about breakage you should take it in to a shop and have them check it by magnaflux the crank .... I would even have it counter weight but some will say no need to counterweight it .. |
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Chickensoup Samba Member
Joined: January 06, 2018 Posts: 5368 Location: Good Hope, GA
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Posted: Wed Nov 18, 2020 8:20 pm Post subject: Re: Likelyhood of breaking a 64 mm crank |
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the issue lies when people over rev a non balanced engine. keep it under 5k, or have it balanced. or better yet just buy a 64mm c/w crank from dpr and have the rotating assembly dynamically balanced. _________________ -'85 c10 5.3 LS, 222 cam, long tubes, x pipe, 3 inch spin tech's
-'05 B5.5 TDI Wagon 17in sport rims ;EGR + BSM + ASV Delete, Stage-2 Tune, straight pipe
'65 Tourist Delivery Build
'66 RIP
'69 RIP
Hosea 4:6 "My people are destroyed for lack of knowledge" |
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esde Samba Member
Joined: October 20, 2007 Posts: 5965 Location: central rust belt
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Posted: Wed Nov 18, 2020 8:36 pm Post subject: Re: Likelyhood of breaking a 64 mm crank |
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Somewhere here I read about having a 69mm crank "destroked" to 64, and using 1600 rods.
This way they got the thicker rod throws like the 1600, but kept it 64mm. WHY, I cannot tell you, but I read it here so it must be true.
Counterweights help minimize crankshaft flex, which helps the crank (and case) live longer. _________________ modok wrote:
Bent cranks are silent but gather no moss. I mean, ah, something like that. |
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Chickensoup Samba Member
Joined: January 06, 2018 Posts: 5368 Location: Good Hope, GA
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Posted: Thu Nov 19, 2020 5:30 am Post subject: Re: Likelyhood of breaking a 64 mm crank |
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1600 rods are longer than 40hp. wont be a direct swap. plus, you would need adifferent flywheel _________________ -'85 c10 5.3 LS, 222 cam, long tubes, x pipe, 3 inch spin tech's
-'05 B5.5 TDI Wagon 17in sport rims ;EGR + BSM + ASV Delete, Stage-2 Tune, straight pipe
'65 Tourist Delivery Build
'66 RIP
'69 RIP
Hosea 4:6 "My people are destroyed for lack of knowledge" |
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bcrazy Samba Member
Joined: October 24, 2009 Posts: 231 Location: Oslo
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Posted: Thu Nov 19, 2020 5:51 am Post subject: Re: Likelyhood of breaking a 64 mm crank |
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If i go down this route I will not split the case.
So another crank is out of the question
(my other option it so build on a 1600 with AB case, but do not want to discuss this here.. )
I just want to know the probability of the stock 64 mm crank breaking under ~55 hp/5000 rpm |
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Jacks Samba Member
Joined: July 15, 2006 Posts: 2347 Location: San Clemente, Ca.
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Posted: Thu Nov 19, 2020 11:25 am Post subject: Re: Likelyhood of breaking a 64 mm crank |
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I have a ‘64 40hp under my workbench wit a broken crank _________________ Jack Staggs
Actual name |
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esde Samba Member
Joined: October 20, 2007 Posts: 5965 Location: central rust belt
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Posted: Thu Nov 19, 2020 11:43 am Post subject: Re: Likelyhood of breaking a 64 mm crank |
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bcrazy wrote: |
If i go down this route I will not split the case.
So another crank is out of the question
(my other option it so build on a 1600 with AB case, but do not want to discuss this here.. )
I just want to know the probability of the stock 64 mm crank breaking under ~55 hp/5000 rpm |
Probably pays to have your current crank magna fluxed, shot peened, and balanced, to give it the best odds of living. I've no idea what the probability of it breaking is. But, Ive seen more broken 36 and 40hp cranks than 1600, by
a large margin. _________________ modok wrote:
Bent cranks are silent but gather no moss. I mean, ah, something like that. |
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earthquake Samba Member
Joined: January 10, 2008 Posts: 3984 Location: SANDY VALLEY, NEVADA
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Posted: Thu Nov 19, 2020 11:51 am Post subject: Re: Likelyhood of breaking a 64 mm crank |
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If you were to offset grind a 69mm crank pin to Chevy std size what would the stroke be?
eQ _________________ 74 CLASS 11 LOOK-A-LIKE
69 DUNE BUGGY
79 INTERNATIONAL SCOUT II
05 SCION XB SERIES RELEASE 2[#437]
95 Chevy C3500 dually
98 Ford E150
Link to Kelly J. Nolte 3/20/53 - 11/6/08
https://time-zonelabs.blogspot.com/p/about-kelly.html
DEATH TO CHINGERS!
[From a military recruitment poster in the novel "The Stainless Steel Rat" By Harry Harrison] |
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[email protected] Samba Member
Joined: June 24, 2015 Posts: 718 Location: Rialto. CA
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Posted: Thu Nov 19, 2020 2:08 pm Post subject: Re: Likelyhood of breaking a 64 mm crank |
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earthquake wrote: |
If you were to offset grind a 69mm crank pin to Chevy std size what would the stroke be?
eQ |
I know If you offset a 69 with 36hp journals gives you a 74mm Chevy journals are bigger than the 36hp journals ..but I bet it can be made to a 72,73, or maybe a 74 as well never seen an offset 69mm crank with Chevy jounals so i cant really give an awnser just a guess ..its best to go with the 36hp journals and use AApistons h beam rods back in the days guys use to use the 69crank with 36hp jounals to stroke their engines the down fall was the weak oem 36hp rods so after awhile that set up died not many do it now days but now days they make 36hp h beam rods which are stronger and which the setup would be good ...69crank offset to 36hp journals gives 74 mm with 83mm bore would make it a 1600cc and it would keep it in the vintagespeed oldschool enigine theme..... |
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TinCanFab Samba Member
Joined: April 04, 2006 Posts: 2743 Location: Waterford, California
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Posted: Thu Nov 19, 2020 5:09 pm Post subject: Re: Likelyhood of breaking a 64 mm crank |
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I broke one driving normal. Here are the common reasons I've read on the samba:
-lugging/over revving
-improper machining of the bearing journal during a rebuild, causing a stress point
-someone mentioned Okrasa did tests and determined the 40hp cranks were forged at too low of a temperature?
Mine broke after using in a Bus, but it came from a Beetle. Obviously more load, did that cause the break? Take it as you will _________________ Check out my truck brought back from the dead... http://www.thesamba.com/vw/forum/viewtopic.php?t=420762&highlight=sprayed+blood
They're never really ever finished 58 rag build...
http://www.thesamba.com/vw/forum/viewtopic.php?t=658092 |
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fl59bug Samba Member
Joined: November 23, 2005 Posts: 1976 Location: North Carolina
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Posted: Fri Nov 20, 2020 6:42 am Post subject: Re: Likelyhood of breaking a 64 mm crank |
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In either the Bill Fisher or Tom Wilson book it relates the use of the 83mm big bore P&C kit to crank breakage.
To paraphrase the book, the 83 big bore kit makes the little 40hp engine feel smooth and powerful, and leads the driver to keep their foot in it more, which overrevs the engine, which over time pounds out the center main allowing the crank to flex and finally break.
I can personally attest to the 83s making me want to rev out my '59 bug. I have a '61 tranny, and although I have absolutely no proof it helps, I try not to go above 15 in first, 30 in second, 45 in third and 71 or 72 in fourth.
As stated under-revving (lugging) is also detrimental. |
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Teeroy Samba Member
Joined: April 20, 2003 Posts: 3685 Location: Eastern WA
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Posted: Sat Nov 21, 2020 5:17 pm Post subject: Re: Likelyhood of breaking a 64 mm crank |
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40hp cranks used to break all the time. Get a counter weighted one from DPR and have it all balanced.
If you destroke a 1600 have have to figure out the rods (length and pin size will be wrong for a 40hp).
earthquake I think you end up with a 71mm crank when offset ground. _________________ Pres. Rivercity VW Club www.rcvwclub.org
Founder Derr Wheat Panzers (DWP)
ARR #3
www.autosportsnorthwest.org
Last edited by Teeroy on Sat Nov 21, 2020 6:15 pm; edited 1 time in total |
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esde Samba Member
Joined: October 20, 2007 Posts: 5965 Location: central rust belt
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Posted: Sat Nov 21, 2020 5:56 pm Post subject: Re: Likelyhood of breaking a 64 mm crank |
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Teeroy wrote: |
If you destroke a 1600 have have to figure out the rods (lenght and pin size will be wrong for a 40hp). |
I think you would machine the 40hp rod so it is the same thickness as the 1600 rod, same as using a 1600 crankshaft to stroke a 40hp. _________________ modok wrote:
Bent cranks are silent but gather no moss. I mean, ah, something like that. |
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Teeroy Samba Member
Joined: April 20, 2003 Posts: 3685 Location: Eastern WA
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Posted: Sat Nov 21, 2020 6:16 pm Post subject: Re: Likelyhood of breaking a 64 mm crank |
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True, that would be the easiest/cheapest option. _________________ Pres. Rivercity VW Club www.rcvwclub.org
Founder Derr Wheat Panzers (DWP)
ARR #3
www.autosportsnorthwest.org |
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Chickensoup Samba Member
Joined: January 06, 2018 Posts: 5368 Location: Good Hope, GA
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Posted: Sat Nov 21, 2020 8:10 pm Post subject: Re: Likelyhood of breaking a 64 mm crank |
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esde wrote: |
Teeroy wrote: |
If you destroke a 1600 have have to figure out the rods (lenght and pin size will be wrong for a 40hp). |
I think you would machine the 40hp rod so it is the same thickness as the 1600 rod, same as using a 1600 crankshaft to stroke a 40hp. |
yes but then youd be limited to vw journal unless you had it welded. _________________ -'85 c10 5.3 LS, 222 cam, long tubes, x pipe, 3 inch spin tech's
-'05 B5.5 TDI Wagon 17in sport rims ;EGR + BSM + ASV Delete, Stage-2 Tune, straight pipe
'65 Tourist Delivery Build
'66 RIP
'69 RIP
Hosea 4:6 "My people are destroyed for lack of knowledge" |
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Teeroy Samba Member
Joined: April 20, 2003 Posts: 3685 Location: Eastern WA
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Posted: Sat Nov 21, 2020 10:43 pm Post subject: Re: Likelyhood of breaking a 64 mm crank |
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VW rod journal is the largest/strongest anyway, only reason to go smaller Porsche or Chevy is to help for clearance on larger strokes. _________________ Pres. Rivercity VW Club www.rcvwclub.org
Founder Derr Wheat Panzers (DWP)
ARR #3
www.autosportsnorthwest.org |
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