Is something fishy between these two bobweights?
Thread Starter
Race Director
Joined: Nov 2003
Posts: 12,221
Likes: 446
From: Overland Park Kansas
2020 Corvette of the Year Finalist (appearance mods)
C4 of Year Winner (appearance mods) 2019
Is something fishy between these two bobweights?
This was Dane's (UltraViolet70s) from his build:
I wrote the following numbers down from my builder's card:
Rod Weight: 434g
Rod Weight: 434g
Bearing: 49g
Bearing: 49g
Oil: 4g
Piston & Pin: 584g
Locks: 4g
Rings: 51g
Rod Reciprocating: 180g
BobWeight = 1789
Since our Piston/Pin weights were significantly different, I'm wondering how our bobweights could end up so close?
Is there a mistake on one of our build cards? (Or worse, in one of our balance jobs?)
Originally Posted by UltraViolet70
Rod Weight: 434g
Rod Weight: 434g
Bearing: 49g
Bearing: 49g
Oil: 4g
Piston & Pin: 584g
Locks: 4g
Rings: 51g
Rod Reciprocating: 180g
BobWeight = 1789
Since our Piston/Pin weights were significantly different, I'm wondering how our bobweights could end up so close?
Is there a mistake on one of our build cards? (Or worse, in one of our balance jobs?)
Last edited by GREGGPENN; Mar 20, 2010 at 01:41 PM.
Le Mans Master
Joined: Mar 2004
Posts: 5,107
Likes: 171
From: Dublin CA
it doesn't make sense to me. You would think that the bob weight would represent the pistion and ALL parts that bolt to the crank.
1) how can the pin weigh 1 gram? and the rings 56?
This might help you...It indicates that Eagle "target balances" their cranks.
http://www.enginebuildermag.com/Arti...balancing.aspx
1) how can the pin weigh 1 gram? and the rings 56?
This might help you...It indicates that Eagle "target balances" their cranks.
http://www.enginebuildermag.com/Arti...balancing.aspx
Thread Starter
Race Director
Joined: Nov 2003
Posts: 12,221
Likes: 446
From: Overland Park Kansas
2020 Corvette of the Year Finalist (appearance mods)
C4 of Year Winner (appearance mods) 2019
My concern was whether to bring this to Dane's attention. From looking at formula's, I'm sure my numbers add up. There are a couple that appear slightly off (like locks at 4g and rings at 51g), but the numbers add up.
Best I can figure, Dane's rods must be SUPER light or there was a mistake. My pistons are ~80g's lighter but my rods must be that much heavier than his.
His are written as 560g whereas mine are split into "big end/little end" weights of 434g and 180g. If the total of those two weights is the total rod weight, mine are way heavier! Mine are 4340 Scats.
(FWIW: I was comparing my card to a couple of recent builds just to see how the Wiseco's compared, and how my RA compared in weight. Comparing to Sliding's thread, my rings must be darn heavy -- or they're not really 51g for 2 sets.)
Best I can figure, Dane's rods must be SUPER light or there was a mistake. My pistons are ~80g's lighter but my rods must be that much heavier than his.
His are written as 560g whereas mine are split into "big end/little end" weights of 434g and 180g. If the total of those two weights is the total rod weight, mine are way heavier! Mine are 4340 Scats.
(FWIW: I was comparing my card to a couple of recent builds just to see how the Wiseco's compared, and how my RA compared in weight. Comparing to Sliding's thread, my rings must be darn heavy -- or they're not really 51g for 2 sets.)
