Pro LS Connecting Rod lengths ?
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Launching!
Joined: May 2012
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Pro LS Connecting Rod lengths ? I'm going to put the Summit Pro piston & rod kit in my 5.3 LM7 and was wondering what the benefit or negative of each of the rod lengths and piston's are? and why you might use one or the other kit, I'm going to run a turbo cam & convertor and two gt35 turbos
Summit Racing Equipment Part Number SUM-PR367807 = 6.098 rod, 7cc dish piston
SUM-PR36L7807 = 6.125 rod, 7cc dish piston
all going in a 2002 Z71 Silverado RCSB ( just building a fun truck)
Summit Racing Equipment Part Number SUM-PR367807 = 6.098 rod, 7cc dish piston
SUM-PR36L7807 = 6.125 rod, 7cc dish piston
all going in a 2002 Z71 Silverado RCSB ( just building a fun truck)
There are differences too I believe regarding piston dwell for a short versus long rod but I have no idea how that would affect a FI engine.
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Thanks for the tag @Pro Stock John
The idea behind the two different rod lengths was actually based on the 6.098" version having a .945" diameter pin instead of the .927" pin used in the 6.125" rod. The .945" pin is a bit heavier but it's offset by the .027" shorter rod. It's also 9% stronger than the .927" pin. On either piston, we have plenty of room for our .300"/.185"/.080" target ring land thickness without the pin entering the oil ring groove.
It's our 4" stroker assemblies that use the 6.125"/.927" rod exclusively. That's due to its ability to max ring land thickness with the groove lock spacer. Also, the rod is designed with a different shoulder over the big end to give the necessary clearance for the bottom of a cylinder with the added stroke.
Rod length theory is fun to think about, whether long or short is better for what stroke (Power vs. Intake). Certainly, never sacrifice cubic inches for rod length. The actual differences even between extreme differences are very slight. We've seen this done many times on a variety of engines. There are MANY different changing factors that are much more important. For a deep dive on rod lengths check out Engine Masters Season 5 Episode 54 (Rod Ratio Examined).
The idea behind the two different rod lengths was actually based on the 6.098" version having a .945" diameter pin instead of the .927" pin used in the 6.125" rod. The .945" pin is a bit heavier but it's offset by the .027" shorter rod. It's also 9% stronger than the .927" pin. On either piston, we have plenty of room for our .300"/.185"/.080" target ring land thickness without the pin entering the oil ring groove.
It's our 4" stroker assemblies that use the 6.125"/.927" rod exclusively. That's due to its ability to max ring land thickness with the groove lock spacer. Also, the rod is designed with a different shoulder over the big end to give the necessary clearance for the bottom of a cylinder with the added stroke.
Rod length theory is fun to think about, whether long or short is better for what stroke (Power vs. Intake). Certainly, never sacrifice cubic inches for rod length. The actual differences even between extreme differences are very slight. We've seen this done many times on a variety of engines. There are MANY different changing factors that are much more important. For a deep dive on rod lengths check out Engine Masters Season 5 Episode 54 (Rod Ratio Examined).
Thread Starter
Launching!
Joined: May 2012
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So now I'm an internet Genius on Connecting rods long VS short after a day of research. And still don't know anymore than i did before i started " about " in the real world how a turbo might effect the choice besides -
1) short builds more torque down low on the RPMs
2) Long gives you a bigger tuning window
3) Long gives you piston rock and a shortened life.
4) Short might give you a heaver piston
5) Short might give you a bigger top ring land
6) Long might push the pin into the oil ring ( but if the piston manufacturer added a shield it fixes that issue)
7) the difference in the 2 rods is 1/2 the thickness of a dime.
8) rod angle is a little better with the longer rod -but both are good.
I'm really looking for practical engineer/mechanic using a turbo rather than the academic engineer !
1) short builds more torque down low on the RPMs
2) Long gives you a bigger tuning window
3) Long gives you piston rock and a shortened life.
4) Short might give you a heaver piston
5) Short might give you a bigger top ring land
6) Long might push the pin into the oil ring ( but if the piston manufacturer added a shield it fixes that issue)
7) the difference in the 2 rods is 1/2 the thickness of a dime.
8) rod angle is a little better with the longer rod -but both are good.
I'm really looking for practical engineer/mechanic using a turbo rather than the academic engineer !
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Thread Starter
Launching!
Joined: May 2012
Posts: 227
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Thank You Sr.
I'm thinking i like the 6.098 w/ bigger pin, unless someone chimes in with an opinion that would make not using it with a turbo.
Are the piston tops the same thickness above the top ring?
I'm thinking i like the 6.098 w/ bigger pin, unless someone chimes in with an opinion that would make not using it with a turbo.
Are the piston tops the same thickness above the top ring?
Thanks for the tag @Pro Stock John
The idea behind the two different rod lengths was actually based on the 6.098" version having a .945" diameter pin instead of the .927" pin used in the 6.125" rod. The .945" pin is a bit heavier but it's offset by the .027" shorter rod. It's also 9% stronger than the .927" pin. On either piston, we have plenty of room for our .300"/.185"/.080" target ring land thickness without the pin entering the oil ring groove.
It's our 4" stroker assemblies that use the 6.125"/.927" rod exclusively. That's due to its ability to max ring land thickness with the groove lock spacer. Also, the rod is designed with a different shoulder over the big end to give the necessary clearance for the bottom of a cylinder with the added stroke.
Rod length theory is fun to think about, whether long or short is better for what stroke (Power vs. Intake). Certainly, never sacrifice cubic inches for rod length. The actual differences even between extreme differences are very slight. We've seen this done many times on a variety of engines. There are MANY different changing factors that are much more important. For a deep dive on rod lengths check out Engine Masters Season 5 Episode 54 (Rod Ratio Examined).
The idea behind the two different rod lengths was actually based on the 6.098" version having a .945" diameter pin instead of the .927" pin used in the 6.125" rod. The .945" pin is a bit heavier but it's offset by the .027" shorter rod. It's also 9% stronger than the .927" pin. On either piston, we have plenty of room for our .300"/.185"/.080" target ring land thickness without the pin entering the oil ring groove.
It's our 4" stroker assemblies that use the 6.125"/.927" rod exclusively. That's due to its ability to max ring land thickness with the groove lock spacer. Also, the rod is designed with a different shoulder over the big end to give the necessary clearance for the bottom of a cylinder with the added stroke.
Rod length theory is fun to think about, whether long or short is better for what stroke (Power vs. Intake). Certainly, never sacrifice cubic inches for rod length. The actual differences even between extreme differences are very slight. We've seen this done many times on a variety of engines. There are MANY different changing factors that are much more important. For a deep dive on rod lengths check out Engine Masters Season 5 Episode 54 (Rod Ratio Examined).
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I'd take the thicker pin w/ the shorter rod.
You're boosting it so it don't care about rod length and all told you aren't putting 100K miles on the engine so the wear characteristics of the options mentioned are moot.
Additionally my comment regarding piston dwell is based on a much larger difference than .027".
The example was a SBC which had a standard rod length of 5.7" and the build featured a 6.25" rod with a custom piston iirc so a much larger difference of .55" compared to .027".
You're boosting it so it don't care about rod length and all told you aren't putting 100K miles on the engine so the wear characteristics of the options mentioned are moot.
Additionally my comment regarding piston dwell is based on a much larger difference than .027".
The example was a SBC which had a standard rod length of 5.7" and the build featured a 6.25" rod with a custom piston iirc so a much larger difference of .55" compared to .027".
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Joined: Jan 2008
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From: Ohio, Georgia, Nevada, Texas
Makes it ideal for boost I bet.
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Joined: Jan 2008
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From: Ohio, Georgia, Nevada, Texas
Thread Starter
Launching!
Joined: May 2012
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Brain @ summit racing;
is this the correct/same parts that are in your kit? ( your sold out in the kit form but if all parts ordered separately i can get. )
is this the correct/same parts that are in your kit? ( your sold out in the kit form but if all parts ordered separately i can get. )
Summit Racing SUM-136SM8531005 - Summit Racing™ Pro LS Piston Rings
Summit Racing SUM-326945780-2P - Summit Racing™ Pro LS Forged Pistons
Summit Racing SUM-LS6098945 - Summit Racing™ Pro LS Connecting Rods
Thread Starter
Launching!
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LS1Tech Sponsor
Joined: Jan 2008
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From: Ohio, Georgia, Nevada, Texas
stacy moore,
The SUM-PR367807 piston and rod kit is shown as not in stock due to the SUM-136SM8531005 piston rings being out of stock. We have a stocking order of those estimated to arrive to us next week. The SUM-PR367807 uses our SUM-326945780-7P 7cc dished pistons and SUM-LS6098945 6.098" rods. Currently, both of those are in stock.
The SUM-PR367807 piston and rod kit is shown as not in stock due to the SUM-136SM8531005 piston rings being out of stock. We have a stocking order of those estimated to arrive to us next week. The SUM-PR367807 uses our SUM-326945780-7P 7cc dished pistons and SUM-LS6098945 6.098" rods. Currently, both of those are in stock.
So now I'm an internet Genius on Connecting rods long VS short after a day of research. And still don't know anymore than i did before i started " about " in the real world how a turbo might effect the choice besides -
1) short builds more torque down low on the RPMs
2) Long gives you a bigger tuning window
3) Long gives you piston rock and a shortened life.
4) Short might give you a heaver piston
5) Short might give you a bigger top ring land
6) Long might push the pin into the oil ring ( but if the piston manufacturer added a shield it fixes that issue)
7) the difference in the 2 rods is 1/2 the thickness of a dime.
8) rod angle is a little better with the longer rod -but both are good.
I'm really looking for practical engineer/mechanic using a turbo rather than the academic engineer !
1) short builds more torque down low on the RPMs
2) Long gives you a bigger tuning window
3) Long gives you piston rock and a shortened life.
4) Short might give you a heaver piston
5) Short might give you a bigger top ring land
6) Long might push the pin into the oil ring ( but if the piston manufacturer added a shield it fixes that issue)
7) the difference in the 2 rods is 1/2 the thickness of a dime.
8) rod angle is a little better with the longer rod -but both are good.
I'm really looking for practical engineer/mechanic using a turbo rather than the academic engineer !
Thread Starter
Launching!
Joined: May 2012
Posts: 227
Likes: 5
stacy moore,
The SUM-PR367807 piston and rod kit is shown as not in stock due to the SUM-136SM8531005 piston rings being out of stock. We have a stocking order of those estimated to arrive to us next week. The SUM-PR367807 uses our SUM-326945780-7P 7cc dished pistons and SUM-LS6098945 6.098" rods. Currently, both of those are in stock.
The SUM-PR367807 piston and rod kit is shown as not in stock due to the SUM-136SM8531005 piston rings being out of stock. We have a stocking order of those estimated to arrive to us next week. The SUM-PR367807 uses our SUM-326945780-7P 7cc dished pistons and SUM-LS6098945 6.098" rods. Currently, both of those are in stock.
A Few more questions;
1) does/will this piston have piston slap until warmed up?
2) with a stock 2002 LM7 5.3 crank what the best rod bearing to use?