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With approx 40 grams heavier for Gen 4 rods, balancing a Gen 3 crank is necessary.
Just wondering for those who have done it, how it comes out?
My engine builder says weight will need to be added to the counterweights.
It’s interesting though. 5.3-6.2 all use the same crank casting number. I can look at all 4 (have one of each here) and the balancing holes in the end counterweights are certainly different, but not radically so.
Also interesting that the LS1 crank is hollow through the mains.
I’m building an LS1. My LS1 crank is pretty groovy, not sure it will polish. So planned to use a mint 5.3 crank. The LQ4 and LS3 cranks aren’t mine.
Anyone know why the LS1 crank is hollow through the mains?
Im sure GM had a reason.
I think the drilled hole through the mains helps a little with bay to bay breathing, same as the windows under the cylinders in the later blocks.
Generally in balancing, wherever you need to add weight to one side, you can remove from 180 out. So if the balancer says you need to add 20g to the counterweight, sometimes you can get lucky and remove it from the rod throw without weakening anything.
My builder pointed that out to me. The 6.0 with Gen 4 rods as well as 6.2 cranks are drilled at the crank throws. I never noticed that. I could look for a Gen 4 6.0 crank.
I’ve run into a pickle with my Gen 4 rods.
I have 8 with ARP 2000 bolts. LQ9 rods from my buddies turbo truck.
Also have 6 from an LS3 with SPS bolts. Also a turbo engine.
Torqued them all up and began measuring the big end for size and roundness.
Only a few are under the high end of the spec. Not good. But then all bets are off when used and from turbo engines.
Just for grins, I swapped in the ARP bolts into the LS3 rods. Was surprised that the size grew by .0001-.0002”.
The SPS bolts are factory type. 15ft/lbs plus 85deg. Wrench says that’s 52 ft lbs. The ARP torque to 45. Might be more if doing the stretch method.
So am now considering the Scat I beams if they make a bushed version. Same weight as the Gen 3 rods, my 5.3 crank would balance easy.
With approx 40 grams heavier for Gen 4 rods, balancing a Gen 3 crank is necessary.
Just wondering for those who have done it, how it comes out?
My engine builder says weight will need to be added to the counterweights.
It’s interesting though. 5.3-6.2 all use the same crank casting number. I can look at all 4 (have one of each here) and the balancing holes in the end counterweights are certainly different, but not radically so.
Also interesting that the LS1 crank is hollow through the mains.
I’m building an LS1. My LS1 crank is pretty groovy, not sure it will polish. So planned to use a mint 5.3 crank. The LQ4 and LS3 cranks aren’t mine.
Anyone know why the LS1 crank is hollow through the mains?
Im sure GM had a reason.
Ron
I am actually doing this now.... I am anxious to see how much weight in heavy metal is needed... do you have any additional insight since your original post? (I am upgrading the Gen3 to Gen4 rods & pistons, and hoping to balance it using my original gen3 Lm7 crank)..
With approx 40 grams heavier for Gen 4 rods, balancing a Gen 3 crank is necessary.
Just wondering for those who have done it, how it comes out?
My engine builder says weight will need to be added to the counterweights.
It’s interesting though. 5.3-6.2 all use the same crank casting number. I can look at all 4 (have one of each here) and the balancing holes in the end counterweights are certainly different, but not radically so.
Also interesting that the LS1 crank is hollow through the mains.
I’m building an LS1. My LS1 crank is pretty groovy, not sure it will polish. So planned to use a mint 5.3 crank. The LQ4 and LS3 cranks aren’t mine.
Anyone know why the LS1 crank is hollow through the mains?
Im sure GM had a reason.
Ron
I am actually doing this now.... I am anxious to see how much weight in heavy metal is needed... do you have any additional insight since your original post? (I am upgrading the Gen3 to Gen4 rods & pistons, and hoping to balance it using my original gen3 Lm7 crank)..
For the record years ago i found on craigslist a ‘01 lq4 block with crank for $500….i purchased a set of gen 4 rods on ebay and a set of .030 over Ls2 flat tops…..a set of chinese 64cc ls3 style heads (that i replaced the valvesprings and seals with GM pieces) and a cam motion 220/230 cam, added a factory ls3 intake and ran it in my nova with no problems at all, it actually hauled ***….a year went by and i got the itch…so i bolted on a LSA supercharger and 2.45” pulley……12k mi later and still no issues and running better than ever…..sure i could have paid more money to have it all balanced and if i were to do it again i probably would….but is it neccisary NO…. I also did the same on a lm7 put gen 4 rods on it with 4.8 flat tops witout balancing and it ran just fine…..its the stroker setups that really need to be balanced
I am actually doing this now.... I am anxious to see how much weight in heavy metal is needed... do you have any additional insight since your original post? (I am upgrading the Gen3 to Gen4 rods & pistons, and hoping to balance it using my original gen3 Lm7 crank)..
Hey,
Because I used the Scat rods which are approx 600gm, no metal needed to be added.
My builder said when using Gen 4 rods, they typically just has to weld up the orig factory drill holes. They don’t need to add heavy metal.
I think the drilled hole through the mains helps a little with bay to bay breathing, same as the windows under the cylinders in the later blocks.
Generally in balancing, wherever you need to add weight to one side, you can remove from 180 out. So if the balancer says you need to add 20g to the counterweight, sometimes you can get lucky and remove it from the rod throw without weakening anything.
Not to sound like an idiot, but how does having hollow mains help bay to bay breathing???
EDIT!!! I just saw Rons pic. So, its not actually thru the main bearing diameters/hollowed crank, it is ADJACENT to the mains. That I understand.....
Last edited by grinder11; Jan 9, 2023 at 11:43 AM.
Not to sound like an idiot, but how does having hollow mains help bay to bay breathing???
EDIT!!! I just saw Rons pic. So, its not actually thru the main bearing diameters/hollowed crank, it is ADJACENT to the mains. That I understand.....
Mike, that hole your looking at is indeed through the mains. The rod journals are offset to either side at 90 degrees…the four of them making it 360 degrees. (90 x 4). The picture looks deceiving I suppose. The hollow mains allow air pressure in each bay to equalize somewhat, along with an overall lighter product.
For the record years ago i found on craigslist a ‘01 lq4 block with crank for $500….i purchased a set of gen 4 rods on ebay and a set of .030 over Ls2 flat tops…..a set of chinese 64cc ls3 style heads (that i replaced the valvesprings and seals with GM pieces) and a cam motion 220/230 cam, added a factory ls3 intake and ran it in my nova with no problems at all, it actually hauled ***….a year went by and i got the itch…so i bolted on a LSA supercharger and 2.45” pulley……12k mi later and still no issues and running better than ever…..sure i could have paid more money to have it all balanced and if i were to do it again i probably would….but is it neccisary NO…. I also did the same on a lm7 put gen 4 rods on it with 4.8 flat tops witout balancing and it ran just fine…..its the stroker setups that really need to be balanced
On your lm7 with gen 4 rods and 4 8 pistons, Did you use the lm7 crank, And what size cam did you use, What was the lift and duration on the cam, I am in the middle of doing this exact same build
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Crank balancing for Gen 4 rods 
