LS7 piston in LS1 connecting rod...
Thread Starter
TECH Regular
Joined: Dec 2003
Posts: 486
Likes: 0
From: Cherry Hill, New Jersey State
I want to use the LS1 connecting rod with a piston sized for a bore of 4.125".
How to know the LS1 piston dtailed information (Compression hight, pin diameter, skirt length, etc...)
Thanks...
How to know the LS1 piston dtailed information (Compression hight, pin diameter, skirt length, etc...)
Thanks...
Teching In
Joined: Jul 2009
Posts: 14
Likes: 0
From: Columbia, MO USA
I prob don't need to say this considering you may be asking about an LS7 "sized" piston rather than an actual GM LS7 piston, but the GM LS7 is a cast piece of junk. It is only appropriate for a stock, or slightly modified configuration.
You could, but you need some machine work to make it happen.
The LS1 rod has a .945" pin and the LS7 piston uses a .925" pin. A machine shop could hone it to .945" and use it with an LS1 pin, unless the length is different.
The compression height is something like 1.175", so with a 6.098" rod and a 4" stroke crank, you're sticking the piston roughly .033" above the deck. You would either need the pistons cut down to reduce compression height or use a thicker Cometics gasket to get quench distance back to a safe level.
For what you're paying a machine shop to do all of that, you may as well buy the correct rods/pistons.
The LS1 rod has a .945" pin and the LS7 piston uses a .925" pin. A machine shop could hone it to .945" and use it with an LS1 pin, unless the length is different.
The compression height is something like 1.175", so with a 6.098" rod and a 4" stroke crank, you're sticking the piston roughly .033" above the deck. You would either need the pistons cut down to reduce compression height or use a thicker Cometics gasket to get quench distance back to a safe level.
For what you're paying a machine shop to do all of that, you may as well buy the correct rods/pistons.
I wouldn't call them junk. The OEM pistons have some great technology built in them, they're just not as strong as the forged pistons.
Thread Starter
TECH Regular
Joined: Dec 2003
Posts: 486
Likes: 0
From: Cherry Hill, New Jersey State
I bought a junk LS1 block, where local machine shop will do dry re-sleeving, where currently I'm experementing the re-sleeving. I would like to use the stock crankshaft & connecting rod since they are good condition and I want to test the block if it is sound well as N/A. This machine shop is known to do sleeving alot on LS1 block with alot of sucess.
The block will be topped with L92 heads, where I will be milling the head to about 0.040" to pump the compression up.
The original LS7 Piston compression hight is 1.173"
1.173" (LS7 Piston C.H.) + 6.067" (LS7 Connecting Rod) + 2" (LS7 Stroke /2) = 9.24" Block Hight.
The original LS1 Piston compression hight is 1.331"
1.331" (LS1 Piston C.H.) + 6.098" (LS1 Connecting Rod) + 1.811" (LS1 Stroke /2) = 9.24" Block Hight.
Option 1, if I used the LS7 piston on stock LS1 connecting rods & stock LS1 crankshaft:
1.173" (LS7 Piston C.H.) + 6.098" (LS1 Connecting Rod) + 1.811" (LS1 Stroke /2) = 9.082"
Difference Between Block High and Rotating Assessmbly = 9.24" - 9.082" = 0.158"
Option 2, if I used the LS7 piston on stock LS7 connecting rods & stock LS1 crankshaft:
1.173" (LS7 Piston C.H.) + 6.067" (LS7 Connecting Rod) + 1.811" (LS1 Stroke /2) = 9.051"
Difference Between Block High and Rotating Assessmbly = 9.24" - 9.051" = 0.189"
Will there be difference in compression ration in option 1 & 2? I think this 0.158" & 0.189" will be added value since I'm milling the heads and will protect the valves heads from hitting the piston, but on the other hand, there will be cost of honing the rod to pin correct size for the 0.158" while in the 0.189" does not require. Please any other thoughts ...
Thanks after all
The block will be topped with L92 heads, where I will be milling the head to about 0.040" to pump the compression up.
The original LS7 Piston compression hight is 1.173"
1.173" (LS7 Piston C.H.) + 6.067" (LS7 Connecting Rod) + 2" (LS7 Stroke /2) = 9.24" Block Hight.
The original LS1 Piston compression hight is 1.331"
1.331" (LS1 Piston C.H.) + 6.098" (LS1 Connecting Rod) + 1.811" (LS1 Stroke /2) = 9.24" Block Hight.
Option 1, if I used the LS7 piston on stock LS1 connecting rods & stock LS1 crankshaft:
1.173" (LS7 Piston C.H.) + 6.098" (LS1 Connecting Rod) + 1.811" (LS1 Stroke /2) = 9.082"
Difference Between Block High and Rotating Assessmbly = 9.24" - 9.082" = 0.158"
Option 2, if I used the LS7 piston on stock LS7 connecting rods & stock LS1 crankshaft:
1.173" (LS7 Piston C.H.) + 6.067" (LS7 Connecting Rod) + 1.811" (LS1 Stroke /2) = 9.051"
Difference Between Block High and Rotating Assessmbly = 9.24" - 9.051" = 0.189"
Will there be difference in compression ration in option 1 & 2? I think this 0.158" & 0.189" will be added value since I'm milling the heads and will protect the valves heads from hitting the piston, but on the other hand, there will be cost of honing the rod to pin correct size for the 0.158" while in the 0.189" does not require. Please any other thoughts ...
Thanks after all
Last edited by LS6; Dec 3, 2011 at 03:16 PM.
Trending Topics
No, these are very poor combinations. There are reasons for the piston to be at (or near) deck height. With 66cc heads and a completely flat-top piston, option #1 results in a 7.59 CR while option #2 shows 7.24 CR. Even if the engine were to start and run, performance would be abysmal...
LS1 Tech Stories
The Best V8 Stories One Small Block at Time
6 Common C5 Corvette Failures and What's Involved In Repairing Them
Pouria Savadkouei
Retro Modern Bandit Pontiac Trans AM Comes With Burt Reynolds' Autograph
Verdad Gallardo
Top 10 Greatest Cadillac V Series Performance Models Ever, Ranked
Pouria Savadkouei
Top 10 Most Powerful Chevy Trucks Ever Made!
Hennessey's New Supercharged Silverado ZR2 Has 700 HP
Verdad Gallardo
Coachbuilt N2A Anteros Is an LS2-Powered C6 Corvette In Italian Clothes
Verdad Gallardo
Awesome K5 Blazer Restomod Comes With C7 Corvette Power
Verdad Gallardo
10 Camaros You Should Never Buy
10 LS Engine Myths That Refuse to Die
Verdad Gallardo
TECH Enthusiast
Joined: May 2008
Posts: 537
Likes: 1
I bought a junk LS1 block, where local machine shop will do dry re-sleeving, where currently I'm experementing the re-sleeving. I would like to use the stock crankshaft & connecting rod since they are good condition and I want to test the block if it is sound well as N/A. This machine shop is known to do sleeving alot on LS1 block with alot of sucess.
The block will be topped with L92 heads, where I will be milling the head to about 0.040" to pump the compression up.
The original LS7 Piston compression hight is 1.173"
1.173" (LS7 Piston C.H.) + 6.067" (LS7 Connecting Rod) + 2" (LS7 Stroke /2) = 9.24" Block Hight.
The original LS1 Piston compression hight is 1.331"
1.331" (LS1 Piston C.H.) + 6.098" (LS1 Connecting Rod) + 1.811" (LS1 Stroke /2) = 9.24" Block Hight.
Option 1, if I used the LS7 piston on stock LS1 connecting rods & stock LS1 crankshaft:
1.173" (LS7 Piston C.H.) + 6.098" (LS1 Connecting Rod) + 1.811" (LS1 Stroke /2) = 9.082"
Difference Between Block High and Rotating Assessmbly = 9.24" - 9.082" = 0.158"
Option 2, if I used the LS7 piston on stock LS7 connecting rods & stock LS1 crankshaft:
1.173" (LS7 Piston C.H.) + 6.067" (LS7 Connecting Rod) + 1.811" (LS1 Stroke /2) = 9.051"
Difference Between Block High and Rotating Assessmbly = 9.24" - 9.051" = 0.189"
Will there be difference in compression ration in option 1 & 2? I think this 0.158" & 0.189" will be added value since I'm milling the heads and will protect the valves heads from hitting the piston, but on the other hand, there will be cost of honing the rod to pin correct size for the 0.158" while in the 0.189" does not require. Please any other thoughts ...
Thanks after all
The block will be topped with L92 heads, where I will be milling the head to about 0.040" to pump the compression up.
The original LS7 Piston compression hight is 1.173"
1.173" (LS7 Piston C.H.) + 6.067" (LS7 Connecting Rod) + 2" (LS7 Stroke /2) = 9.24" Block Hight.
The original LS1 Piston compression hight is 1.331"
1.331" (LS1 Piston C.H.) + 6.098" (LS1 Connecting Rod) + 1.811" (LS1 Stroke /2) = 9.24" Block Hight.
Option 1, if I used the LS7 piston on stock LS1 connecting rods & stock LS1 crankshaft:
1.173" (LS7 Piston C.H.) + 6.098" (LS1 Connecting Rod) + 1.811" (LS1 Stroke /2) = 9.082"
Difference Between Block High and Rotating Assessmbly = 9.24" - 9.082" = 0.158"
Option 2, if I used the LS7 piston on stock LS7 connecting rods & stock LS1 crankshaft:
1.173" (LS7 Piston C.H.) + 6.067" (LS7 Connecting Rod) + 1.811" (LS1 Stroke /2) = 9.051"
Difference Between Block High and Rotating Assessmbly = 9.24" - 9.051" = 0.189"
Will there be difference in compression ration in option 1 & 2? I think this 0.158" & 0.189" will be added value since I'm milling the heads and will protect the valves heads from hitting the piston, but on the other hand, there will be cost of honing the rod to pin correct size for the 0.158" while in the 0.189" does not require. Please any other thoughts ...
Thanks after all
You might want to talk to your machine shop. I don't believe you can dry sleeve an LS1 for a 4.125 inch bore as they are the only ones with coolant between the individual holes and factory liners are thin. LS2 and later blocks are siamesed between bores and can accept a larger liner. Key is the liner OD, not ID - LS1 just does not have enough metal there.
Only real option for LS1 block and 4.125 bore is a wet sleeve. This is a much more difficult install and probably a local guy is not the best choice for this. RED or ERL would be a good choice but be advised this is not a cheap job.
Thread Starter
TECH Regular
Joined: Dec 2003
Posts: 486
Likes: 0
From: Cherry Hill, New Jersey State
I tried to find out piston having bore of 4.125" and the pin diameter 0.945" and the compression hight of 1.331", but no sucess.
It seem that no one done a engine of bore(4.125") X stroke(3.622") with connecting rod of 6.098" before...
Thanks...
It seem that no one done a engine of bore(4.125") X stroke(3.622") with connecting rod of 6.098" before...
Thanks...
What he Said ^ and for the amount of machine work to make a set of LS7 pistons work, you could have had ROSS or JE make you a custom forged set. though I think there's a few problems outlined in this combination.
Thread Starter
TECH Regular
Joined: Dec 2003
Posts: 486
Likes: 0
From: Cherry Hill, New Jersey State
I have approched one piston manufacture for a custom made and waiting for their answer. Today, the LS1 block is sucessfully dry sleeved in the shop. I can not confirm the block integrity is sound well unless I put under load and start the engine. I will see soon how it goes.
If I can not find the 4.125" piston's, I think I will go with the LS3 Piston's. I want to see the sleeving integrity is sound good and to use the engine for high RPM. Could you please elaborate more about the combination issue...
Thanks...
If I can not find the 4.125" piston's, I think I will go with the LS3 Piston's. I want to see the sleeving integrity is sound good and to use the engine for high RPM. Could you please elaborate more about the combination issue...
Thanks...
Thread Starter
TECH Regular
Joined: Dec 2003
Posts: 486
Likes: 0
From: Cherry Hill, New Jersey State
Update:
I went with the LS3 piston (4.0845" bore) with the same pin diameter of LS3 stock and compression hight of 1.330". The machine shop ensured with this re-sleeving, I can go to 4.150" as maximum, but the 4.125" & 4.15" bore piston's are not avilabe as shelf items.
I will be later on my next project ordering a custom pistons of 4.15" bore.
I went with the LS3 piston (4.0845" bore) with the same pin diameter of LS3 stock and compression hight of 1.330". The machine shop ensured with this re-sleeving, I can go to 4.150" as maximum, but the 4.125" & 4.15" bore piston's are not avilabe as shelf items.
I will be later on my next project ordering a custom pistons of 4.15" bore.
Thread Starter
TECH Regular
Joined: Dec 2003
Posts: 486
Likes: 0
From: Cherry Hill, New Jersey State
This is the junk block after sleeve installation. The Block cost me $ 130 USA. The sleeve cost $100 USD (8 QTY), machine shop cost $ 240 USD, Psitons cost $ 413 USD (8 QTY), Piston's ring's cost $ 130 USD (for 8 Piston's)
