another balance question
Moderator: Team
another balance question
New pistons came in 17 gr heavier @411 gr. with rings. The old pins weighed 106 gr @ 0.787 x 2.250 x 0.200, H13. There is an H13 DLC 0.180 wall tapered pin available that weighs 91 gr. Problem solved. My questions are: a) is this enough pin and b) is 17 grams even enough to be concerned about. Total bob weight is 1356 gr, max engine speed will be 9400.
Re: another balance question
"Don't worry, be happy." The balance machine can pick up 17g, but it won't make any difference when running.
If you're concerned about the pins call the manufacturer and ask their tech guys.
If you're concerned about the pins call the manufacturer and ask their tech guys.
-
- Guru
- Posts: 4610
- Joined: Sun Sep 18, 2011 11:31 am
- Location: Heading for a bang up with Andromeda as we all are.
Re: another balance question
A lot of engineers state that even 25 grams of unbalance is not a issue, but this it at 7000 or so rpm, at 9400 I would want far better tolerance then 17!
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!
-
- Guru
- Posts: 1765
- Joined: Wed Aug 26, 2009 8:30 pm
- Location: Beautiful Southern Maryland
- Contact:
Re: another balance question
What engine is it ?
Bill Koustenis
Advanced Automotive Machine
Waldorf Md
www.enginerepairshop.com
Advanced Automotive Machine
Waldorf Md
www.enginerepairshop.com
Re: another balance question
When Bill Jenkins was running Pro Stock with a SBC he would over balance @ 52%. I have over and under balanced 35g and more. It didn't run any better or any worse, also the bearings looked like new on tear down.
-
- Pro
- Posts: 397
- Joined: Tue Dec 29, 2015 8:09 pm
- Location: TN
Re: another balance question
My biggest concern would be going to a heavier piston and a thinner wall pin. The weights involved in how it will balance out is secondary. I’m assuming a drag race application and 9400 RPM is at the shift/stripe. I’d talk to the piston/pin manufacturer for some possible guidance. If the current piston and pin combo looks good it may be marginal with the new stuff especially with the forces Involved at that RPM. My hunch is you’ll be ok but skimping on the pin to save weight is my last resort unless there’s a comfortable safety margin there.
-
- Guru
- Posts: 2694
- Joined: Fri Jan 09, 2009 8:51 pm
- Location: Australia
Re: another balance question
I put pistons that were 45g heavier in a motor without a rebalance.
It turns 8200rpm & looks mint on pull down.
Just run it, you'll never know the difference.
It turns 8200rpm & looks mint on pull down.
Just run it, you'll never know the difference.
-
- Guru
- Posts: 4610
- Joined: Sun Sep 18, 2011 11:31 am
- Location: Heading for a bang up with Andromeda as we all are.
Re: another balance question
My main concern would also be for the unneeded weight placing a greater load on the Rods.
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!
Re: another balance question
This was also the opinion of the man that did the original balance. His shop serviced engines for several ARCA teams back in the day. If you compare with the total bobweight, it amounts to 1.2%KnightEngines wrote: ↑Fri Nov 08, 2019 1:28 am I put pistons that were 45g heavier in a motor without a rebalance.
It turns 8200rpm & looks mint on pull down.
Just run it, you'll never know the difference.
-
- Pro
- Posts: 461
- Joined: Sun Feb 13, 2005 11:27 am
- Location:
-
- Guru
- Posts: 4610
- Joined: Sun Sep 18, 2011 11:31 am
- Location: Heading for a bang up with Andromeda as we all are.
Re: another balance question
Just talking in general since we strive for light weight to have a more rev happy motor.
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!