LT1 rotating assembly in L98 question
Thread Starter
Racer
Joined: Jul 2008
Posts: 347
Likes: 4
From: Woodstown NJ
LT1 rotating assembly in L98 question
Hi,
I have a question about rebuilding my 91 L98 with LT1 guts. I can pick up a crank, rods, pistons, flex plate, and balancer for 100.00. The rods are powdered metal which are far stronger than the stock l98 rods. The crank has to be used because it is weighted for the light rods and Pistons. Since this assembly is zero balance can I use the L98 front dampener? Do I have to have the flex plate balanced to the motor or is it just zero balance?
I have a question about rebuilding my 91 L98 with LT1 guts. I can pick up a crank, rods, pistons, flex plate, and balancer for 100.00. The rods are powdered metal which are far stronger than the stock l98 rods. The crank has to be used because it is weighted for the light rods and Pistons. Since this assembly is zero balance can I use the L98 front dampener? Do I have to have the flex plate balanced to the motor or is it just zero balance?
Racer
Joined: Nov 2005
Posts: 258
Likes: 4
From: Iuka Mississippi
This is interesting because i have a 1991 L-98 and a LT1 that i`ll never use. A couple of the concerns would be are they each internal or externally balanced and are the crank snouts exactly the same. I`ll be listening along.
Le Mans Master
Joined: Jun 2009
Posts: 6,528
Likes: 752
From: South Dakota
It interests me too.
I don't know if they can be used or not, but I believe the balance methods should be the same.
The dual mass flywheel is the same between LT1 and L98 cars including no difference in flywheel weighting. The flywheels for both are not zero balanced. They are balanced for the LT4/LT1/L98 engines and can be used interchangeably.
Team Owner
Joined: Aug 2004
Posts: 21,543
Likes: 3,216
From: Park City Utah
I can't see why it wouldn't work. I'd try it, if I were in your position.
I believe that the crank snout is different; the LT1 is not key'd...the L98 is. I don't think that matters much if you're careful setting the L98 damper on the LT1 crank so your timing marks are useful. I think you'd have to use the L98 damper in order to use the L98 crank pulley and have it line up w/the L98 accessories....but you could experiment or measure both to see if they end up w/the same offset or not for the belt drive.
I believe that the crank snout is different; the LT1 is not key'd...the L98 is. I don't think that matters much if you're careful setting the L98 damper on the LT1 crank so your timing marks are useful. I think you'd have to use the L98 damper in order to use the L98 crank pulley and have it line up w/the L98 accessories....but you could experiment or measure both to see if they end up w/the same offset or not for the belt drive.
Team Owner
Joined: Sep 2003
Posts: 25,394
Likes: 2,741
I can't see why it wouldn't work. I'd try it, if I were in your position.
I believe that the crank snout is different; the LT1 is not key'd...the L98 is. I don't think that matters much if you're careful setting the L98 damper on the LT1 crank so your timing marks are useful. I think you'd have to use the L98 damper in order to use the L98 crank pulley and have it line up w/the L98 accessories....but you could experiment or measure both to see if they end up w/the same offset or not for the belt drive.
I believe that the crank snout is different; the LT1 is not key'd...the L98 is. I don't think that matters much if you're careful setting the L98 damper on the LT1 crank so your timing marks are useful. I think you'd have to use the L98 damper in order to use the L98 crank pulley and have it line up w/the L98 accessories....but you could experiment or measure both to see if they end up w/the same offset or not for the belt drive.
http://www.enginebuildermag.com/1999...-lt1-engine-2/
I'd use this as maybe a starting point to START from and then maybe find a couple discussions that agree OR maybe just visit a reliable "local" builder.
"RT" might be able to confirm the "crank-snout" since he seems to have one of each!
Last edited by WVZR-1; Jul 28, 2016 at 10:28 AM.
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Le Mans Master
Joined: Sep 2013
Posts: 6,192
Likes: 750
From: near the thumb in the mitten
LT1 is not "Zero" balanced front half is rear half requires weight on flywheel / flex plate. You want to be sure you have a "Zero balance" balancer. The 96-97 engines used a different crank key than the 92-95 because of crank sensor. Using that key should locate balancer, or you could have machine shop add key way for it. Good Luck
Safety Car
Joined: Jul 1999
Posts: 3,946
Likes: 63
From: Marianna FL
If I remember correctly, the 96-97 crank key is flush with the crank where the balancer goes over it. It only extends through the reluctor ring. The hub for the 96 is not broached for a key. All he will need is a standard half moon key and a keyed balancer hub. I'd imagine the L98 one meets all those requirements.
Le Mans Master
Joined: Sep 2013
Posts: 6,192
Likes: 750
From: near the thumb in the mitten
That is true. On gen 1 sbc the balancer seats against crank gear for timing chain. The part of key way that would hold reluctor will hold balancer. As long as balancer bolt is torqued it should stay put.
Burning Brakes
Joined: Sep 2008
Posts: 810
Likes: 58
From: Alva Florida
I have an LT1 in my garage...please keep us posted on your results!!
1) More compression 11:1
2) Somewhat stronger internals ~ Hyperutectic pistons?
3) Lighter pistons also if I remember correctly
Sounds like an excellent idea!
1) More compression 11:1
2) Somewhat stronger internals ~ Hyperutectic pistons?
3) Lighter pistons also if I remember correctly
Sounds like an excellent idea!
Race Director
Joined: Apr 2000
Posts: 15,344
Likes: 4,009
From: Texas
Have you had the cylinders in the block checked? If the cylinders need 10 thousandths or more of clean up, you won't be able to use the LT1 pistons.
Unless you're doing a "dirt cheap & pray" rebuild, you'll like need to have the crank cleaned up or possibly turned, rods resized, etc. Sometimes "cheap" isn't so cheap by the time it's all done correctly.
Unless you're doing a "dirt cheap & pray" rebuild, you'll like need to have the crank cleaned up or possibly turned, rods resized, etc. Sometimes "cheap" isn't so cheap by the time it's all done correctly.
Last edited by 96GS#007; Jul 29, 2016 at 09:51 AM.
Thread Starter
Racer
Joined: Jul 2008
Posts: 347
Likes: 4
From: Woodstown NJ
Have you had the cylinders in the block checked? If the cylinders need 10 thousandths or more of clean up, you won't be able to use the LT1 pistons.
Unless you're doing a "dirt cheap & pray" rebuild, you'll like need to have the crank cleaned up or possibly turned, rods resized, etc. Sometimes "cheap" isn't so cheap by the time it's all done correctly.
Unless you're doing a "dirt cheap & pray" rebuild, you'll like need to have the crank cleaned up or possibly turned, rods resized, etc. Sometimes "cheap" isn't so cheap by the time it's all done correctly.
Last edited by ZCarr; Jul 30, 2016 at 11:34 AM.
Thread Starter
Racer
Joined: Jul 2008
Posts: 347
Likes: 4
From: Woodstown NJ
I am going to have the block checked out. it still has the factory machine marks in it so maybe a hone will do. I am going to have the rods and crank machined as well. I didn't plan on using the factory LT1 pistons. A new set is less than 200 with rings and I want to see if I can get CR to ~10:1 without shaving the new heads. I need to have machine work done anyway and the LT1 rotating assembly is a better starting point than the L98 stuff. They are the PM rods and I plan on putting ARP bolts in them so they should be safe at 6500 rpm if I ever get a mini ram later on down the road.
This is being done as cheap as possible as I only have until Oct to finish the car. The future wife wants her Dad to drive her to the Chapel in the car since its white and I have a moderate problem with Corvettes. I went right grad school payments to wedding payments so the bottom end has deviated from the original plan but the LT1 stuff should be pretty stout.
Melting Slicks
Joined: Jan 2009
Posts: 3,482
Likes: 196
From: folsom california
10:1 is easy unless the pistons have more than a 4 or 5cc "dish"; 4 or 5 cc being the usual "dish' to accommodate the valve reliefs. There are any of a number of "compression calculators" online that can tell you all you need to know.
Last edited by mtwoolford; Jul 30, 2016 at 01:34 PM.
Thread Starter
Racer
Joined: Jul 2008
Posts: 347
Likes: 4
From: Woodstown NJ
I have a set of AFR180 head with 64cc chambers. I would prefer not to have them shaved in case I ever want to sell them down the road. I have to talk to the engine shop about what Pistons I can get that will give me decent compression if I don't shave them. Plus I don't have a working knowledge of how to calculate the quench and all that good stuff
10:1 is easy unless the pistons have more than a 4 or 5cc "dish"; 4 or 5 cc being the usual "dish' to accommodate the valve reliefs. There are any of a number of "compression calculators" online that can tell you all you need to know.[/QUOTE]
10:1 is easy unless the pistons have more than a 4 or 5cc "dish"; 4 or 5 cc being the usual "dish' to accommodate the valve reliefs. There are any of a number of "compression calculators" online that can tell you all you need to know.[/QUOTE]