Rod orientation.
Thread Starter
Staging Lane
Joined: Jul 2024
Posts: 93
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Rod orientation. My gen4 rods all came out with the "dimple" facing towards the rear. I've been doing tons of research, but it seems everyone has a different opinion.
Some say it makes no difference on a stock crank, only aftermarket.
I look at the chamfers on the rods and one side is machined, and the other is not. Some say the machined chamfer should go towards the crank counterweight, away from the other rod on that throw.
That would make only half the dimples towards the rear, the other half forward.
So, "un-confuse" me.
I want to install the pistons this week.
Thanks.
Some say it makes no difference on a stock crank, only aftermarket.
I look at the chamfers on the rods and one side is machined, and the other is not. Some say the machined chamfer should go towards the crank counterweight, away from the other rod on that throw.
That would make only half the dimples towards the rear, the other half forward.
So, "un-confuse" me.
I want to install the pistons this week.
Thanks.
TECH Resident
Joined: Mar 2012
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From: Texas
Can you please be more specific? We don't all speak... Whatever that is.
Anyway, 4th gen rods are omnidirectional. The BUMP on the 4th gen rods (it's not a dimple) points to the back of the engine from the factory, although I've heard many tales of people opening engines to find them pointing to the front, or one side pointing back, and to other to the front.
I assemble them pointing to the rear.
Anyway, 4th gen rods are omnidirectional. The BUMP on the 4th gen rods (it's not a dimple) points to the back of the engine from the factory, although I've heard many tales of people opening engines to find them pointing to the front, or one side pointing back, and to other to the front.
I assemble them pointing to the rear.
Thread Starter
Staging Lane
Joined: Jul 2024
Posts: 93
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Currently I have the pistons on the rods with the "bump" to the rear.
I think IGN-1A was referring to the groove between the crank counterweights and rods and just missed the other "o", which is the reason, it's said, that it doesn't matter which way they go.
I was debating swapping 4 of them to point the bump forward, but not sore if it's a good idea, or whether it even matters.
I think IGN-1A was referring to the groove between the crank counterweights and rods and just missed the other "o", which is the reason, it's said, that it doesn't matter which way they go.
I was debating swapping 4 of them to point the bump forward, but not sore if it's a good idea, or whether it even matters.
An LS OEM crank does not have a radius at the counterweight. You can assemble the OEM rods either direction. I’ve done it purposely in mock-up to measure cheek clearances.
Aftermarket LS cranks have a radius, and aftermarket LS rods have a chamfer on one side, so the aftermarket stuff matters.
Aftermarket LS cranks have a radius, and aftermarket LS rods have a chamfer on one side, so the aftermarket stuff matters.
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Staging Lane
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Thanks.
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TECH Apprentice
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Che70velle is correct, I just make it my rule to always install the chamfer toward the crank. Some engines have offset pin ends and it's easier for me to follow the simple rule so I don't have to worry about reversing anything.
Thread Starter
Staging Lane
Joined: Jul 2024
Posts: 93
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More confusion, according to this 'site; https://www.engineprofessional.com/TB23/TB062923-2.pdf the smaller flat of the rod should be forward.
If that's correct then the "bump" on the rod would be to the front.
I really want this right the first time.
Right now I have half of the rod bumps forward, because the machined chamfer side of the rods is against the crank, the un-machined chamfer is to the opposing rod.
This makes the most sense to me because there is more rod movement between the crank and rod than between the opposing rods, and the slight chamfer should allow more oil into the space between the rods and crank for lubrication.
Please verify.
Thank you.
If that's correct then the "bump" on the rod would be to the front.
I really want this right the first time.
Right now I have half of the rod bumps forward, because the machined chamfer side of the rods is against the crank, the un-machined chamfer is to the opposing rod.
This makes the most sense to me because there is more rod movement between the crank and rod than between the opposing rods, and the slight chamfer should allow more oil into the space between the rods and crank for lubrication.
Please verify.
Thank you.
Man this has been beat to death over the years. Gen4 rod orientation doesn’t matter. The dimple is simply a character mark…has nothing to do with placement. There is no offset to the rods, and there’s no radius on the OEM crank. They can go either direction. I’ve built no telling how many…rods can go either way.
Man this has been beat to death over the years. Gen4 rod orientation doesn’t matter. The dimple is simply a character mark…has nothing to do with placement. There is no offset to the rods, and there’s no radius on the OEM crank. They can go either direction. I’ve built no telling how many…rods can go either way.
If you want to be just like it came from factory, all dimples/ dots faced rear rearward.
They only do this to speed up production on the assembly line. They only need to produce 1 piston, 1 rod, and have 1 orientation to assemble...
Otherwise as stated above, it does not matter because the OEM crank does not have a radius in the journal. Technically it has an undercut but that's a different discussion.
If Scotts done it, You can take it to the bank that it works!
TECH Enthusiast
Joined: Aug 2021
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Backward piston notch My "tech" was taught to me by Fred Carrillo, how to fit the connrod.
I need to know this because I like to install the pistons backwards.
Lance
I need to know this because I like to install the pistons backwards.
Lance
Last edited by IGN-1A; Aug 12, 2025 at 07:10 PM.
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