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Gne 4 LQ4 rod/piston orientation dimples

 
Old 03-01-2019, 09:26 PM
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Default Gne 4 LQ4 rod/piston orientation dimples

So I've seen so many mixed opinions on which way my gen 4 lq4 rods go. The rods have dimples on one side. I've heard the dimples on the rods face backwards and the dots on the pistons face forwards. I've also heard it doesn't matter. Can someone please help me put this to bed?
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Old 03-01-2019, 09:58 PM
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Casper, it’s been done both ways without issue. The dimples aren’t there for orientation. Always look at the rods big end cheek chamfer for proper placement with most any rod except maybe certain piston guided setups. If the crankshaft has a radius at the rod journal edge, which Oem LS cranks do not have, Aftermarket cranks do have, then you would make sure to orient your connecting rods chamfer to the outside of the journal. So since the LS cranks don’t have the radius, and the rods don’t have the chamfer, it really doesn’t matter which way they face. Personally I turn all mine toward the front, but it’s just a matter of preference.
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Old 03-01-2019, 10:03 PM
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Originally Posted by Che70velle View Post
Casper, itís been done both ways without issue. The dimples arenít there for orientation. Always look at the rods big end cheek chamfer for proper placement with most any rod except maybe certain piston guided setups. If the crankshaft has a radius at the rod journal edge, which Oem LS cranks do not have, Aftermarket cranks do have, then you would make sure to orient your connecting rods chamfer to the outside of the journal. So since the LS cranks donít have the radius, and the rods donít have the chamfer, it really doesnít matter which way they face. Personally I turn all mine toward the front, but itís just a matter of preference.
thanks so much! The next question I have then is if the orientation doesn't matter than why do the rods have a chamfer? They could be orientated chamfer on chamfer, flat on flat or chamfer on flat, correct?
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Old 03-02-2019, 01:16 PM
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Originally Posted by CasperCasper View Post
thanks so much! The next question I have then is if the orientation doesn't matter than why do the rods have a chamfer? They could be orientated chamfer on chamfer, flat on flat or chamfer on flat, correct?
The connecting rod orientation does absolutely matter! DO NOT mistake what was posted above!

The orientation of the bulge on the shaft of the connecting rod is not important, because the location of that bulge varies between different model connecting rods.

Just as " Che70velle" stated... LOOK ONLY at the big end of the connecting rod!

The flatter side of the big end of the connecting rod always faces another connecting rod flat side (IE: two connecting rods facing one another, mirrored).

The chamfered side of the big end of the connecting rod always faces towards the main journal and bearing.

If the piston has a direction mark (or dot, or arrow) ,the piston will "Almost ALWAYS" have that directional mark intended to be directed towards the front of the engine.

There are rare situations where this piston rule does not apply, however unless working with custom parts... This exception to the rule should not be experienced.
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Old 03-02-2019, 01:22 PM
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I forgot to state that the chamfered side of the connecting rod is only meant to meet the mirrored angle chamfer on the crankshaft. This is know as the crankshaft journal fillet.

While most of the LSx engines have crankshafts with minimal crankshaft journal fillets (And most people think that they are not even there) Do not stray from what I tell you here.

When I was a powertrain engineer with GM... This topic of a small or un-pronounced crankshaft journal fillet was discussed in-house as a joke that will plague the high performance rebuilder for an eternity...
The factory procedure for assembly and for repair all follow the normal rule for structural integrity.
The DIYer often does not know to follow the standard rule and can get away with the incorrect orientation to some extent do to loose fitment/ tolerances.

NEVER put a flat side towards a chamfered side component!
One there will be metal wearing away and getting circulated through the engine oiling system in most engines (excluding most LSx stock engines)
Two this combination would create a structural weakness.

DO NOT, DO NOT attempt this.

Last edited by vorteciroc; 03-02-2019 at 01:36 PM.
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Old 03-02-2019, 01:49 PM
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Wow vortec, thanks for your great response.
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Old 03-02-2019, 06:24 PM
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Heres the smooth machined chamfer side


Heres the rough chanfer as cast side

I didn't realize both sides are chamfered. Does this mean the smooth machined chamfer both face outwards towards the crank weight?
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Old 03-02-2019, 06:41 PM
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Originally Posted by CasperCasper View Post

Heres the smooth machined chamfer side


Heres the rough chanfer as cast side

I didn't realize both sides are chamfered. Does this mean the smooth machined chamfer both face outwards towards the crank weight?
As you noticed one of the small chamfers is smooth and the other side has the chamfer rough cast.

On the stock connecting rods... the chamfer is very small as is the crank journal fillet.

The first photo would have the connecting rod face the crankshaft journal fillet and the second photo would would have the connecting rod face another connecting rod.

What you see on these connecting rods essentially would be a double sided flat faced connecting rod compared to traditional NON-LSx based factory connecting rods.
Neither side really has a true chamfer that would ride against a traditional crankshaft journal fillet.
Both sides have a teeny tiny chamfer that would make-up a traditional flat side.
On these connecting rods (As you noticed), one side has a machined smooth chamfer... most people are oblivious to this, it seems...

So usually with these particular connecting rods, I state that:

The visual difference on the connecting rods pictured, would be the difference in the flat machined material at the fracture point of the connecting rod.
The side with the wider flat machined surface, faces another connecting of the mirrored surface.

Last edited by vorteciroc; 03-02-2019 at 06:48 PM.
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Old 03-02-2019, 10:00 PM
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Originally Posted by vorteciroc View Post
I forgot to state that the chamfered side of the connecting rod is only meant to meet the mirrored angle chamfer on the crankshaft. This is know as the crankshaft journal fillet.

While most of the LSx engines have crankshafts with minimal crankshaft journal fillets (And most people think that they are not even there) Do not stray from what I tell you here.

When I was a powertrain engineer with GM... This topic of a small or un-pronounced crankshaft journal fillet was discussed in-house as a joke that will plague the high performance rebuilder for an eternity...
The factory procedure for assembly and for repair all follow the normal rule for structural integrity.
The DIYer often does not know to follow the standard rule and can get away with the incorrect orientation to some extent do to loose fitment/ tolerances.

NEVER put a flat side towards a chamfered side component!
One there will be metal wearing away and getting circulated through the engine oiling system in most engines (excluding most LSx stock engines)
Two this combination would create a structural weakness.

DO NOT, DO NOT attempt this.
Iíve actually put LS engines together ďincorrectlyĒ to prove the point that it doesnít matter. Since the OEM LS cranks have a rolled fillet and not a traditional raidus, what is supposed to happen of the rod is flipped the other way? In my experience, there has been no consequence.
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Old 03-02-2019, 10:10 PM
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I agree, On LSx based engines there will be not metal debris produced.

I only state one should follow the normal orientation due to habit formation.

Metal debris and structural integrity concerns are inevitable outside of these factory LSx based parts...
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Old 03-03-2019, 12:06 AM
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From the factory, the Dimples on the Floating Rod's all face rearward while the dots on the top of the pistons face forward.

As mentioned by KCS it really doesn't matter on the LSX based engines.
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