Will an all LT1 rotating assembly fit an L98 block? I know you can not mix a LT1 and L98 rotating assembly parts due to balancing problem. But, as a hole crank, rods, and pistons will it work?

 

New,

Here you go again, eh?

Yes. The bearing spacing, sizes, radii, and everything are the same. Since you are only talking "L98" to "LT1", and they both have a one-piece rear main seal, they are a direct interchange.

You are absolutely correct about the balance issue. Lighter pistons forced a balance shift in all LT1 engines. If you get a late 1994 or later LT1, you can be sure you'll get the PM rods as well, which will save a bit more mass. Earlier LT1s, like the 1993 'Y' car and some of the early '94s got plain old cast billet/forged rods that were heavier and not as strong. By 1995, ALL LT1s had the lighter, stronger powdered metal con rods. You can't mix and match these either. However, none of the LT1 parts will match well to the L98 crank. As a matter of fact, the SBC 305 crank is a closer match to the LT1 parts for dynamic balance, but is still just a little on the heavy side. If you can get a complete LT1 rotating assembly, get it. Make SURE that includes the harmonic balancer and hub (two pieces), and the Woodruff key for the hub (since it's special with a cut-back). You might want to grab the flexplate, too. Again, a '95 or later will assure you of getting the best rotataing assembly.

The '94 I had apart seemed to be very well balanced as delivered from the factory - far better than most SBC engines. I attribute that to the consistent mass of the rods and pistons as a result of the material and manufactiring process.

Additionally, I have heard but not been able to confirm that ALL the LT1 and L99 cranks were cast of nodular iron instead of gray iron. That would be just another benefit of using the entire assembly. I'm positive that all LT4 cranks were nodular, but not sure of the LT1s and L99s. I couldn't tell just by looking.

Keep it up, and you'll have an "LT-98-B9 SBC 1½" or something like that very soon. The lighter, stronger bottom end surely won't hurt you a bit.

 

I figured a house was a littl emore important than a bowtie 406 right now. I'm at a time in my tinkering that I want to try something different. We will see what happens with the lest amount of money spent. A true low buget build up.

 

I have a 51K mile crank, rods, pistons, balancer, flex plate from a 96' LT1. I am trying to find a std. bore 350 roller block to use the guts in. But, it looks like I can't use the crank or balancer in an L98 based engine. And, from what I gather - if I used the rods & pistons w/ an L98 crank, I would have to get the rotating assembly balanced.

 

If the L98 is an '87 or later, there should be no problems with the crank installation. As a matter of fact, the early LT1s ('93) used the same crank casting number as the L98. I don't understand where the problems might lie.

 

Vader, thanks for the response. Basically... I have that rotating assembly from the 96' LT1 motor. Some L98 aluminum heads, a stock 85' Vette TPI unit, the 96' LT1 roller cam & lifters, an & 89' Vette accessory drive. All I lack is a block. I want to put all this stuff together because I have little or no money in all of it, then it's going in a 39' ford w/ a 700R4. Basically I need a cheap, and smooth running EFI motor for a street rod application. Do you see any problems with the combination of parts I am trying to mix & match?

 

remember that LT1 engine pistons are designed for moderate compression with their 58cc chambers putting them in a engine and putting on 64cc heads would result in crappy compression (read low)

 

Aluminum L98 heads are 58cc - not 64.

 

that would be perfect for achieving stock LT1 compression then

 

i have a 94 lt1 shortblock...

how can i find out if i have forged or pm rods?