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RCP Phx Samba Member
Joined: November 20, 2021 Posts: 496 Location: Phoenix,AZ
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Posted: Sat Jun 25, 2022 8:52 am Post subject: What are your balancing tolerances? |
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Putting together another stroker and I'm curious what you all accept/expect for tolerances?
BTW, I'm dealing with a Scat crank, Scat rods, and Racetec pistons. |
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58ragman Samba Member
Joined: September 29, 2014 Posts: 404 Location: OC to ontario
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Posted: Sat Jun 25, 2022 12:27 pm Post subject: Re: What are your balancing tolerances? |
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.2 tenths of a gram |
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58ragman Samba Member
Joined: September 29, 2014 Posts: 404 Location: OC to ontario
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Posted: Sat Jun 25, 2022 12:28 pm Post subject: Re: What are your balancing tolerances? |
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so say rods are 471.6 grams the close rod would be like 471.4 grams thats is how close it needs to be if your paying the doe.
it would only be 4 rods so it is possible.
its done all the time on american V8 shit same with pistons rings pins etc |
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RCP Phx Samba Member
Joined: November 20, 2021 Posts: 496 Location: Phoenix,AZ
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Posted: Sat Jun 25, 2022 3:37 pm Post subject: Re: What are your balancing tolerances? |
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That's kind of my dilemma, I built this same motor 2 yrs ago for me. I managed to get a combination of the parts to achieve .25grams difference between the combo's. This time I can only get to 2.3 grams at best do to the rods having a 3.2 gram difference in weight. They are end weight matched directly from Scat! |
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58ragman Samba Member
Joined: September 29, 2014 Posts: 404 Location: OC to ontario
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Posted: Sat Jun 25, 2022 6:10 pm Post subject: Re: What are your balancing tolerances? |
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yeah the current rods i heard are all over the place with tolerances but find the lightest and match them all to that one. rods are balanced to each other and also end for end kind of tricky |
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RCP Phx Samba Member
Joined: November 20, 2021 Posts: 496 Location: Phoenix,AZ
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Posted: Sat Jun 25, 2022 6:33 pm Post subject: Re: What are your balancing tolerances? |
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I don't have the equipment to end balance rods and it's not my motor that's why I asked about general acceptable tolerances since this is not a high rpm/ high HP motor build. |
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modok Samba Member
Joined: October 30, 2009 Posts: 26740 Location: Colorado Springs
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Posted: Sat Jun 25, 2022 7:06 pm Post subject: Re: What are your balancing tolerances? |
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1% weight difference is limit for stock
0.5% for HIGH performance
you can go down to a tenth of a percent but I don't believe it has any REAL benefit. |
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chrisflstf Samba Member
Joined: February 10, 2004 Posts: 3412 Location: San Diego
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RCP Phx Samba Member
Joined: November 20, 2021 Posts: 496 Location: Phoenix,AZ
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Posted: Sat Jun 25, 2022 8:36 pm Post subject: Re: What are your balancing tolerances? |
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I would love to get more input on this before I make any recommendations but the assembly would definitely comply with the 0.5% rule. |
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madmike Samba Member
Joined: July 11, 2005 Posts: 5291 Location: Atlanta,Michigan
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Posted: Sun Jun 26, 2022 3:50 am Post subject: Re: What are your balancing tolerances? |
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I take my time and balance everything to 0 ,,,,yep zero Perfect _________________ 'Black Ice'Drag Buggy 'Turbo'
Rail Buggy 1915 turbo
76 Drag/Street bug 2180cc 'Turbo' 11:85 @113 mph"If I go any faster I'll burn up the Hamster" ,gets 28 mpg. also 10/09/22 11.90 @115 mph
"If I'm ever on Life Support,UNPLUG Me, Then Plug me back In see if that Works" |
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RCP Phx Samba Member
Joined: November 20, 2021 Posts: 496 Location: Phoenix,AZ
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Posted: Sun Jun 26, 2022 8:22 am Post subject: Re: What are your balancing tolerances? |
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Again I'm just donating my time for the build as a favor to Russ at Bishop-Buehl in California. The client I have only met twice but it is definitely his call! I'm only in the pre-preassembly stages right now checking all the parts and weights! |
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modok Samba Member
Joined: October 30, 2009 Posts: 26740 Location: Colorado Springs
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Posted: Sun Jun 26, 2022 10:52 am Post subject: Re: What are your balancing tolerances? |
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Sorry for the mixed messages, bit confusing.
I could make some alternate accounts and argue with myself ,
Never have but think about it more and more.
That would help to kind of BRING OUT a lot more perspective, from, lets say all the interesting characters I learned from in the past, because, well, they can't bring themselves back to life.
If you are balancing the rods and pistons to 2x the tolerance of what the crank is balanced to then your probably wasting your time on the wrong part or just in general.
Balancing the whole crank and flywheel assembly down to one gram at the stroke diameter is rather hard to do repeatedly.
Scats rods USUALLY are matched to 1.5 grams difference total weight in a set but I don't think that is a guarantee it's just what they typically manage these days. |
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RCP Phx Samba Member
Joined: November 20, 2021 Posts: 496 Location: Phoenix,AZ
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Posted: Sun Jun 26, 2022 9:31 pm Post subject: Re: What are your balancing tolerances? |
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I went ahead and did the wrist pins and the pistons, they are now +/- .01 grams! |
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modok Samba Member
Joined: October 30, 2009 Posts: 26740 Location: Colorado Springs
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Posted: Mon Jun 27, 2022 1:11 am Post subject: Re: What are your balancing tolerances? |
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1/3 ounce inches was as good as older crank balancing machines could do.
So that's about 6 grams at a 3" stroke
More modern machinery CAN go to half that, not always practical. You can be chasing ghosts of low spots around oil holes or vibration in the belt drive....only if everything is running totally SMOOTH will it be real.
Raby is going with 0.2 ounce inches these days, so he says.
And rods within 0.5 grams
https://aircooledtechnology.com/dynamic-balancing/
You want to balance the rods? Just need some skateboard wheel bearings, bit of sheetmetal and some string. maybe 2 hour project.
Some of the setup tools may look intimidating, but the key is to support the rod at the exact centers of the two bores.......which isn't THAT hard to do. |
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slayer61 Samba Member
Joined: June 01, 2021 Posts: 999 Location: CA
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Posted: Mon Jun 27, 2022 7:19 am Post subject: Re: What are your balancing tolerances? |
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madmike wrote: |
I take my time and balance everything to 0 ,,,,yep zero Perfect |
Yup. The shop I worked at in the '70s had a digital dope scale. 1/100 of a gram _________________
Cusser wrote: |
... Most folks are idiots when it deals with electrical !!! |
67rustavenger wrote: |
3/4 race cam? What's missing, one of the lobes? |
Paul
'68 Manx clone... Sears??
2276 built on AS21 case
W-125 w/ GB 1.25:1 rockers
Mahle forged pistons
CB 4340 crank
CB H beam rods
deep sump
44 HPMX
EMPI GTV 2 STG II wedge ports
CB Magna spark
1 5/8 merged collector w/ hater stinger |
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RCP Phx Samba Member
Joined: November 20, 2021 Posts: 496 Location: Phoenix,AZ
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Posted: Mon Jun 27, 2022 8:02 am Post subject: Re: What are your balancing tolerances? |
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I wouldn't hesitate a second on buying a good rod balancing jig except for the fact I would still have to send out the cranks to get balanced! |
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nsracing Samba Member
Joined: November 16, 2003 Posts: 9437 Location: NOVA
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Posted: Mon Jun 27, 2022 3:43 pm Post subject: Re: What are your balancing tolerances? |
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I have been meaning to machine some rod/rig for balancing. But I am just not in mood to go in the garage.
For street use - half-gram is plenty...on rods and pistons.
For race use - 1/tenth gram is the usual on rods and pistons.
The crank/flywheel/pressure plt/ pulley - balance them down to the lowest tolerance you can afford. this be - 0.2 ounce inch tolerance good for 9500 RPM.
YOu nee a dynamic balancer for the rotating parts.
I just set a friend of mine in TX - a Stewart Warner 2000 dynamic balancer. Not sure if he is taking work right now.
I can do the balance job if you care to send this way. |
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Lingwendil Samba Member
Joined: February 25, 2009 Posts: 3987 Location: Antioch, California, a block from the hood
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Posted: Mon Jun 27, 2022 4:47 pm Post subject: Re: What are your balancing tolerances? |
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I picked up a nice digital type scale that was repeatably accurate to within .1 grams, so I just matched all parts for weight when I did my rods and pistons, easy but time consuming. I'm happy with the extra work when added to the fact that just in mocking up alone I took the engine apart a dozen times. What's another hour? I'm not getting paid by the hour and I'm not likely to ever build an engine more than once every few years. _________________ 73 super beetle thread http://www.thesamba.com/vw/forum/viewtopic.php?t=649622 Back on the Road!
Modify your Kadrons for SVDA http://www.thesamba.com/vw/forum/viewtopic.php?p=8115884#8115884
Cast iron VJU4BR8 SVDA reference thread- https://www.thesamba.com/vw/forum/viewtopic.php?t=...mp;start=0
Need replacement filters for original Kadron aircleaners? WIX #42087 is a perfect fit, as is Napa Gold #2087! |
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mark tucker Samba Member
Joined: April 08, 2009 Posts: 23937 Location: SHALIMAR ,FLORIDA
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Posted: Thu Jun 30, 2022 9:54 am Post subject: Re: What are your balancing tolerances? |
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mike is correct. why would you waste &$ time almost balancing something? |
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nsracing Samba Member
Joined: November 16, 2003 Posts: 9437 Location: NOVA
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Posted: Sat Jul 02, 2022 5:04 am Post subject: Re: What are your balancing tolerances? |
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That is like saying why need a .50 cal when you can kill it w/ .22
If you want to vaporize it— need more. |
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