Re: Balancing 440 rod question?
[Re: dragon slayer]
#2978174
10/25/21 12:04 PM
10/25/21 12:04 PM
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Joined: Oct 2007
Posts: 4,213 New York
polyspheric
master
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master
Joined: Oct 2007
Posts: 4,213
New York
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Big end (rotating) weight is 100% compensated in the CW. Small end (reciprocating weight) is 50% compensated in the CW (for V8) 50 grams light on the small end = -25 grams in the CW 50 grams heavy on the big end = +50 grams in the CW Net: +25 grams heavy in the CW
Boffin Emeritus
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Re: Balancing 440 rod question?
[Re: B1MAXX]
#2978225
10/25/21 01:42 PM
10/25/21 01:42 PM
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Joined: Jun 2014
Posts: 1,342 VA
dragon slayer
OP
pro stock
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OP
pro stock
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VA
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You could under one big end and hang it with the heavy one. Bob weights are set to one journal (2 assemblies). But I think you've done a good job to get where you are at with only 8 rods to work with. I don't think over all weight is that important. Nowhere on a typical bob weight work sheet is overall, just top/bottom. Understand the process. Some methods have you weight big end and subtract it from total to get small end weight. Others recommend weighing both ends. So in the end total weight is in play. Just not used in the bob weight calculation. If I took off 8 grams to get big end to match, I would be well under the small end at that point as total weight should be down too. I guess the point of big end compensated for at 100% matters, plus the small end is only a small portion of the reciprocating weight considering piston and pin. So better to have a difference on the rod small end, versus the big end which is the major contributor to rotating weight. Appreciate the inputs.
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Re: Balancing 440 rod question?
[Re: dragon slayer]
#2978232
10/25/21 01:54 PM
10/25/21 01:54 PM
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Joined: Aug 2011
Posts: 2,872 Pattison Texas
CSK
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master
Joined: Aug 2011
Posts: 2,872
Pattison Texas
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if the pins are real long you could grind some off the ends, none floating type just a thought
1968 Charger COLD A/C Hilborn EFI 512ci 9.7 compression, Stealth heads, 4.10 gear A518 ODtrans 4100lb,10.93 full street car trim 2020 T/A 392 Stock 11.79 @ 114.5
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Re: Balancing 440 rod question?
[Re: dragon slayer]
#2978265
10/25/21 03:08 PM
10/25/21 03:08 PM
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Joined: Mar 2011
Posts: 3,105 Michigan
A727Tflite
master
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master
Joined: Mar 2011
Posts: 3,105
Michigan
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You could under one big end and hang it with the heavy one. Bob weights are set to one journal (2 assemblies). But I think you've done a good job to get where you are at with only 8 rods to work with. I don't think over all weight is that important. Nowhere on a typical bob weight work sheet is overall, just top/bottom. Understand the process. Some methods have you weight big end and subtract it from total to get small end weight. Others recommend weighing both ends. So in the end total weight is in play. Just not used in the bob weight calculation. If I took off 8 grams to get big end to match, I would be well under the small end at that point as total weight should be down too. I guess the point of big end compensated for at 100% matters, plus the small end is only a small portion of the reciprocating weight considering piston and pin. So better to have a difference on the rod small end, versus the big end which is the major contributor to rotating weight. Appreciate the inputs. Was under the impression you were to find the lightest small end and match the other 7 to that weight. Then do the same for the big end. Why wouldn’t the overall weight be the same then? Not any different than when you check weight distribution on a car. Measure the front then the rear. The total Is the total.
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Re: Balancing 440 rod question?
[Re: dragon slayer]
#2978269
10/25/21 03:40 PM
10/25/21 03:40 PM
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Joined: Oct 2007
Posts: 4,213 New York
polyspheric
master
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master
Joined: Oct 2007
Posts: 4,213
New York
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From the standpoint of geometry and physics, only the piston pin, rod bushing, and some surrounding material is reciprocating weight (and above the pin centerline it's moving in the opposite direction). Only the crankpin, big end shells and part of the cap and beam are rotating weight (and below the crankpin centerline it's moving in the opposite direction). The rod beam between these 2 centers is both reciprocating and rotating weight, with the percentage of each determined by its portion of the rod's length (not the weight). More of my comments on my site here: http://victorylibrary.com/mopar/crank-bal.htm
Boffin Emeritus
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Re: Balancing 440 rod question?
[Re: moparx]
#2978279
10/25/21 03:58 PM
10/25/21 03:58 PM
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Joined: Aug 2011
Posts: 2,872 Pattison Texas
CSK
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master
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Pattison Texas
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would the pin weight be then added to the rod small end weight ? You are correct, MY BRAIN misfired backwords LOL
1968 Charger COLD A/C Hilborn EFI 512ci 9.7 compression, Stealth heads, 4.10 gear A518 ODtrans 4100lb,10.93 full street car trim 2020 T/A 392 Stock 11.79 @ 114.5
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Re: Balancing 440 rod question?
[Re: lewtot184]
#2978284
10/25/21 04:22 PM
10/25/21 04:22 PM
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Joined: Oct 2007
Posts: 4,213 New York
polyspheric
master
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master
Joined: Oct 2007
Posts: 4,213
New York
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"V" engines cannot be perfectly balanced. Even engines theoretically in perfect primary balance (L6, V12) have rocking couple. The 50% frequently used in V8 is not mathematically calculated, but "what works".
Boffin Emeritus
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Re: Balancing 440 rod question?
[Re: A727Tflite]
#2978410
10/25/21 10:18 PM
10/25/21 10:18 PM
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Joined: Jun 2014
Posts: 1,342 VA
dragon slayer
OP
pro stock
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OP
pro stock
Joined: Jun 2014
Posts: 1,342
VA
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You could under one big end and hang it with the heavy one. Bob weights are set to one journal (2 assemblies). But I think you've done a good job to get where you are at with only 8 rods to work with. I don't think over all weight is that important. Nowhere on a typical bob weight work sheet is overall, just top/bottom. Understand the process. Some methods have you weight big end and subtract it from total to get small end weight. Others recommend weighing both ends. So in the end total weight is in play. Just not used in the bob weight calculation. If I took off 8 grams to get big end to match, I would be well under the small end at that point as total weight should be down too. I guess the point of big end compensated for at 100% matters, plus the small end is only a small portion of the reciprocating weight considering piston and pin. So better to have a difference on the rod small end, versus the big end which is the major contributor to rotating weight. Appreciate the inputs. Was under the impression you were to find the lightest small end and match the other 7 to that weight. Then do the same for the big end. Why wouldn’t the overall weight be the same then? Not any different than when you check weight distribution on a car. Measure the front then the rear. The total Is the total. It is not that simple because as mention the physic/geometry. I measured the small ends today, and remeasured big ends. Then remeasured total, the problem is the added values do not exactly match total weight. One end is suspended and only one is on the scale. Plus there is a density of the rod issue and you do run into rods that have seem to have a higher density. I examined the pads and they are similiar in shape. Right now I have all the rods total weight correct, but there are differences in 2 rods where they have lighter small ends, but heavier big ends. I am also almost out of small area pads on these rods. These are way better then as installed by Mopar where one was about 25 grams off, but frankly at least one rod is not really workable with the set. I do have a replacement I can use. It was just the weirdness that the lightest rod had the heaviest big end and a lighter small end.
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Re: Balancing 440 rod question?
[Re: dragon slayer]
#2978425
10/25/21 11:13 PM
10/25/21 11:13 PM
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Joined: Mar 2011
Posts: 3,105 Michigan
A727Tflite
master
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master
Joined: Mar 2011
Posts: 3,105
Michigan
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You could under one big end and hang it with the heavy one. Bob weights are set to one journal (2 assemblies). But I think you've done a good job to get where you are at with only 8 rods to work with. I don't think over all weight is that important. Nowhere on a typical bob weight work sheet is overall, just top/bottom. Understand the process. Some methods have you weight big end and subtract it from total to get small end weight. Others recommend weighing both ends. So in the end total weight is in play. Just not used in the bob weight calculation. If I took off 8 grams to get big end to match, I would be well under the small end at that point as total weight should be down too. I guess the point of big end compensated for at 100% matters, plus the small end is only a small portion of the reciprocating weight considering piston and pin. So better to have a difference on the rod small end, versus the big end which is the major contributor to rotating weight. Appreciate the inputs. Was under the impression you were to find the lightest small end and match the other 7 to that weight. Then do the same for the big end. Why wouldn’t the overall weight be the same then? Not any different than when you check weight distribution on a car. Measure the front then the rear. The total Is the total. It is not that simple because as mention the physic/geometry. I measured the small ends today, and remeasured big ends. Then remeasured total, the problem is the added values do not exactly match total weight. One end is suspended and only one is on the scale. Plus there is a density of the rod issue and you do run into rods that have seem to have a higher density. I examined the pads and they are similiar in shape. Right now I have all the rods total weight correct, but there are differences in 2 rods where they have lighter small ends, but heavier big ends. I am also almost out of small area pads on these rods. These are way better then as installed by Mopar where one was about 25 grams off, but frankly at least one rod is not really workable with the set. I do have a replacement I can use. It was just the weirdness that the lightest rod had the heaviest big end and a lighter small end. Like I said before - it’s no different than measuring a car across the scales. Measure the front and measure the rear and add them together and you get total car weight. In order to correctly weigh a rod the beam HAS to be perfectly horizontal and you need the proper fixture to suspend the rod at the small or big end. Using the wrong tools or using the correct tools incorrectly will get you the wrong numbers. Density, cap size, shape is irrelevant.
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Re: Balancing 440 rod question?
[Re: A727Tflite]
#2978464
10/26/21 06:38 AM
10/26/21 06:38 AM
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Joined: Jan 2003
Posts: 6,435 Abilene, Texas
fastmark
master
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master
Joined: Jan 2003
Posts: 6,435
Abilene, Texas
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I tell you what I’ve decided even in my stock builds. By the time you have a competent performance machine shop, press the old pistons off, install ARP rod bolts, resize the rods, go to the extra work and the extra expense of matching/balancing the rods, checking the lengths and then pressing them back on the new pistons, you can buy a nice set of new rods. Even Molnar’s are in my builds budgets.
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Re: Balancing 440 rod question?
[Re: fastmark]
#2978475
10/26/21 07:40 AM
10/26/21 07:40 AM
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Joined: May 2005
Posts: 2,013 Apollo, PA.
B1MAXX
top fuel
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top fuel
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Posts: 2,013
Apollo, PA.
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This person is dealing with 8 stock rods with one rod 20+grams off the others and variations end to end. Buy a set of h-beams, a gram here or there, no problem. Put yourself in their shoes. What do you do? Grind 10-20 gr off a cap/little end ? Do some of you even know what 10-20 grams of grinding would look like.These are the skills/knowledge we are losing. I see most people anymore just spend lots of money, let someone else do it, and watch youtube videos. This would make a great shop class test Just one more comment, you should grind perpendicular to the rods bores center-line. (op)What are the 8 big/little end measurements now?
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Re: Balancing 440 rod question?
[Re: fastmark]
#2978484
10/26/21 08:27 AM
10/26/21 08:27 AM
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Joined: Jan 2003
Posts: 13,404 Marion, South Carolina [><]
an8sec70cuda
I Live Here
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I Live Here
Joined: Jan 2003
Posts: 13,404
Marion, South Carolina [><]
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I tell you what I’ve decided even in my stock builds. By the time you have a competent performance machine shop, press the old pistons off, install ARP rod bolts, resize the rods, go to the extra work and the extra expense of matching/balancing the rods, checking the lengths and then pressing them back on the new pistons, you can buy a nice set of new rods. Even Molnar’s are in my builds budgets. Man, it's crazy shops are charging you $700 to rebuild a set of stock rods. It's nothing like that around here.
CHIP '70 hemicuda, 575" Hemi, 727, Dana 60 '69 road runner, 440-6, 18 spline 4 speed, Dana 60 '71 Demon, 340, low gear 904, 8.75 '73 Chrysler New Yorker, 440, 727, 8.75 '90 Chevy 454SS Silverado, 476" BBC, TH400, 14 bolt '06 GMC 2500HD LBZ Duramax
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Re: Balancing 440 rod question?
[Re: an8sec70cuda]
#2978501
10/26/21 09:28 AM
10/26/21 09:28 AM
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Joined: Jan 2004
Posts: 8,356 fredericksburg,va
cudaman1969
master
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master
Joined: Jan 2004
Posts: 8,356
fredericksburg,va
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Not sure if mentioned but my stock Hemi rods are all rounded on the small end, I don’t see how they could ‘make them the same weight’. Same with the h beam rods I have
Last edited by cudaman1969; 10/26/21 09:30 AM.
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