Explain this GM 602/604 Crank Balancing numbers
Moderator: Team
Explain this GM 602/604 Crank Balancing numbers
I'm curious if anyone could explain to me what is going on here with these balancing numbers as instructed by GM on their sealed race 602/604 engines. I'm not an engine builder or professional, but these are weird.
You do not have the required permissions to view the files attached to this post.
-
- Guru
- Posts: 4607
- Joined: Sun Sep 18, 2011 11:31 am
- Location: Heading for a bang up with Andromeda as we all are.
Re: Explain this GM 602/604 Crank Balancing numbers
Real good question!
Since 3 out of the 4 pin ends listed veri a lot in weight then one would have to assume that 3 different types of pins and or rod type ends could have possibly been used in those two motors in your question.
I don't know if these motors when done in normal GM production line fashion, by if so then the final balance was done by spinning the assembled short block up with the heads still off.
If they did it that way then they could at that point make up for the weight difference.
If you look in a GM parts book and find different part number listings for Rods and or pins for these two motors then that might explain it.
Since 3 out of the 4 pin ends listed veri a lot in weight then one would have to assume that 3 different types of pins and or rod type ends could have possibly been used in those two motors in your question.
I don't know if these motors when done in normal GM production line fashion, by if so then the final balance was done by spinning the assembled short block up with the heads still off.
If they did it that way then they could at that point make up for the weight difference.
If you look in a GM parts book and find different part number listings for Rods and or pins for these two motors then that might explain it.
You can cut a man's tongue from his mouth, but that does not mean he’s a liar, it just shows that you fear the truth he might speak about you!
- Dave Koehler
- Vendor
- Posts: 7207
- Joined: Mon Oct 04, 2004 11:19 pm
- Location: Urbana, IL USA
- Contact:
Re: Explain this GM 602/604 Crank Balancing numbers
While the end result works out something is going on there relative to position.
Center 2 are identical.
Front is heavier than the rear
Averaging the weights out ,the first one is the lightest assembly and the last 2 are the heaviest assemblies FWIW.
It might help to see the cranks side by side. Also wondering what is hanging off the front and rear of the engine. Does that play a part?
It will be nice to figure this out.
The last thing I need is another trick balance job being requested by internet crew chiefs.
Center 2 are identical.
Front is heavier than the rear
Averaging the weights out ,the first one is the lightest assembly and the last 2 are the heaviest assemblies FWIW.
It might help to see the cranks side by side. Also wondering what is hanging off the front and rear of the engine. Does that play a part?
It will be nice to figure this out.
The last thing I need is another trick balance job being requested by internet crew chiefs.
Dave Koehler - Koehler Injection
Enderle Fuel Injection - Nitrous Charger - Balancing - Nitrous Master software
http://www.koehlerinjection.com
"Never let a race car know that you are in a hurry."
Enderle Fuel Injection - Nitrous Charger - Balancing - Nitrous Master software
http://www.koehlerinjection.com
"Never let a race car know that you are in a hurry."
Re: Explain this GM 602/604 Crank Balancing numbers
One crank (12556307) is forged steel crank with 2.1 rod and 2.45 mains
One crank (10243068) is cast iron with 2.0 rods and 2.65 mains
One crank (14088526) is cast iron with 2.1 rods and 2.45 mains.
One crank (10243068) is cast iron with 2.0 rods and 2.65 mains
One crank (14088526) is cast iron with 2.1 rods and 2.45 mains.
-
- Pro
- Posts: 414
- Joined: Sat Aug 23, 2008 7:12 am
- Location:
Re: Explain this GM 602/604 Crank Balancing numbers
Bobweights to balance an external balance crank without damper and flywheel perhaps?
Re: Explain this GM 602/604 Crank Balancing numbers
I think this is the best crank balancing, piston/rod weight thread there is.
Everyone is ReBalancing for three grams...
General Motors... Hold my beer!
Everyone is ReBalancing for three grams...
General Motors... Hold my beer!
Magnús Aðalvíkingur Finnbjörnsson
- Dave Koehler
- Vendor
- Posts: 7207
- Joined: Mon Oct 04, 2004 11:19 pm
- Location: Urbana, IL USA
- Contact:
Re: Explain this GM 602/604 Crank Balancing numbers
1: If that were the case the end journal numbers would be greater than the middle two....in a normal scenario.strokersix wrote: ↑Thu Nov 04, 2021 2:15 pm Bobweights to balance an external balance crank without damper and flywheel perhaps?
2: Since it appears to be deliberate I wonder if they are trying to counter some crank flex. How is that for far out?
3: I am upset that they would publish that without some explanation.
4: It's pretty much impossible to acquire a replacement rod or piston 3 yrs later that comes close to the original part weight.
This will be a nightmare.
5: I really hate engineers raised on common core math.
Dave Koehler - Koehler Injection
Enderle Fuel Injection - Nitrous Charger - Balancing - Nitrous Master software
http://www.koehlerinjection.com
"Never let a race car know that you are in a hurry."
Enderle Fuel Injection - Nitrous Charger - Balancing - Nitrous Master software
http://www.koehlerinjection.com
"Never let a race car know that you are in a hurry."
Re: Explain this GM 602/604 Crank Balancing numbers
One thing I forgot is on these vortec motors, the flexplate has a small weight on it. This is standard issue.
I've never seen personally or heard of balancing where you have 3 different weights hanging off your crankshaft and I can't imagine this is the mathematics for balancing the assembly without the balancer and vortec flexplate.. that would be insane
I've never seen personally or heard of balancing where you have 3 different weights hanging off your crankshaft and I can't imagine this is the mathematics for balancing the assembly without the balancer and vortec flexplate.. that would be insane
- Dave Koehler
- Vendor
- Posts: 7207
- Joined: Mon Oct 04, 2004 11:19 pm
- Location: Urbana, IL USA
- Contact:
Re: Explain this GM 602/604 Crank Balancing numbers
Do you know if these are internal or external assemblies?Bos's5.0 wrote: ↑Thu Nov 04, 2021 3:32 pm One thing I forgot is on these vortec motors, the flexplate has a small weight on it. This is standard issue.
I've never seen personally or heard of balancing where you have 3 different weights hanging off your crankshaft and I can't imagine this is the mathematics for balancing the assembly without the balancer and vortec flexplate.. that would be insane
Dave Koehler - Koehler Injection
Enderle Fuel Injection - Nitrous Charger - Balancing - Nitrous Master software
http://www.koehlerinjection.com
"Never let a race car know that you are in a hurry."
Enderle Fuel Injection - Nitrous Charger - Balancing - Nitrous Master software
http://www.koehlerinjection.com
"Never let a race car know that you are in a hurry."
Re: Explain this GM 602/604 Crank Balancing numbers
I know the vortec flexplate looks like this.Dave Koehler wrote: ↑Thu Nov 04, 2021 3:34 pmDo you know if these are internal or external assemblies?Bos's5.0 wrote: ↑Thu Nov 04, 2021 3:32 pm One thing I forgot is on these vortec motors, the flexplate has a small weight on it. This is standard issue.
I've never seen personally or heard of balancing where you have 3 different weights hanging off your crankshaft and I can't imagine this is the mathematics for balancing the assembly without the balancer and vortec flexplate.. that would be insane
https://www.jegs.com/i/Chevrolet-Perfor ... 1/10002/-1
8" balancer but I'm still searching for the part no.
Re: Explain this GM 602/604 Crank Balancing numbers
10243068 is also 2.45 main 2.10 rod. Production L31 crankshaft.
-
- Pro
- Posts: 414
- Joined: Sat Aug 23, 2008 7:12 am
- Location:
Re: Explain this GM 602/604 Crank Balancing numbers
I'm not sure about that.Dave Koehler wrote: ↑Thu Nov 04, 2021 2:38 pm
1: If that were the case the end journal numbers would be greater than the middle two....in a normal scenario.
My understanding. The point of external balance is because there wasn't room to make the crank counterweights big enough. I have never balanced a crankshaft so below may be all wrong:
Bobweight is opposite the crank counterweight. External balance is aligned with counterweight. Missing external balance weight effectively means a smaller counterweight. Then you need less bobweight opposite the smaller counterweight to balance the crank without damper and flywheel.
Logical explanation but like I said, could be all wrong. Correction welcome.
-
- Guru
- Posts: 1762
- Joined: Wed Aug 26, 2009 8:30 pm
- Location: Beautiful Southern Maryland
- Contact:
Re: Explain this GM 602/604 Crank Balancing numbers
That is totally odd The specs say it needs an external balance flywheel. I would love to see the rest of the tech documents. Or as Paul Harvey used to say "The rest of the story"
https://static.speedwaymotors.com/pdf/19258602.pdf
https://www.speedwaymotors.com/Chevrole ... 67820.html
https://static.speedwaymotors.com/pdf/19258602.pdf
https://www.speedwaymotors.com/Chevrole ... 67820.html
Bill Koustenis
Advanced Automotive Machine
Waldorf Md
www.enginerepairshop.com
Advanced Automotive Machine
Waldorf Md
www.enginerepairshop.com
- Dave Koehler
- Vendor
- Posts: 7207
- Joined: Mon Oct 04, 2004 11:19 pm
- Location: Urbana, IL USA
- Contact:
Re: Explain this GM 602/604 Crank Balancing numbers
More alien common core math mysteries.
Why is a 350 called a 602?
Why is a 350 called a 602?
Dave Koehler - Koehler Injection
Enderle Fuel Injection - Nitrous Charger - Balancing - Nitrous Master software
http://www.koehlerinjection.com
"Never let a race car know that you are in a hurry."
Enderle Fuel Injection - Nitrous Charger - Balancing - Nitrous Master software
http://www.koehlerinjection.com
"Never let a race car know that you are in a hurry."
Re: Explain this GM 602/604 Crank Balancing numbers
Nobody balances a crank like that. You get your ONE bobweight from the parts you have, install the flywheel/flexplate and the dampner on the front and see how far off the balance is, and go from there. YOu either add weight to the crank, or take it off. There is NO 3 bobweight system.strokersix wrote: ↑Thu Nov 04, 2021 4:00 pmI'm not sure about that.Dave Koehler wrote: ↑Thu Nov 04, 2021 2:38 pm
1: If that were the case the end journal numbers would be greater than the middle two....in a normal scenario.
My understanding. The point of external balance is because there wasn't room to make the crank counterweights big enough. I have never balanced a crankshaft so below may be all wrong:
Bobweight is opposite the crank counterweight. External balance is aligned with counterweight. Missing external balance weight effectively means a smaller counterweight. Then you need less bobweight opposite the smaller counterweight to balance the crank without damper and flywheel.
Logical explanation but like I said, could be all wrong. Correction welcome.