ZCarr

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?

ZCarr

No ome here has done this?

mtwoolford

balance everything as an unit; you'll still need rod bearings and piston rings for the balance job, possibly the damper also.

RICHARD TILL

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.

QCVette

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.

Tom400CFI

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.

WVZR-1

I believe that I've seen this discussed and gets very confusing. I do believe that the crank is cut for the key-way ......BUT .. here's maybe a good basic read to research from ...

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!

LTxDave

The crank on my 95 is keyed, the balancer hub is not. As far as I know, both engines are neutral balanced at front and external at the rear. Should be plug and play.

Kevova

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

LTxDave

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.

Kevova

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.

cadmaniac

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!

96GS#007

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.

ZCarr

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.

ZCarr

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.

mtwoolford

As I recall I had a cast iron head version of your engine out of a 86 Caprice and the combustion chambers were a nominal 58 cc; 57.6 cc as actually measured; with flat top pistons and a thin head gasket the compression was close to 11:1.

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.

ZCarr

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]