So I've been back and forth between Jeg's and Summit and the experts at Eagle and have heard a few things. Seems the most you can stroke a 346ci LS1 is to a 393? Which seems to be bull****, because I thought the biggest you could go with that block was a 427, and even then, THATS pushing it! I've seen numbers over 500 with the 408 and thats the ideal motor I want to go with. But Jeg's told me the only company they had produced a stroker kit for it was J&E, and they were having problems with the piston skirt hitting the crank on the way back down, obvious clearance issues. So I called Eagle since they seem to be pretty popular with these motors and they tell me they had a kit for it, for almost $2700 (through Summit). The kicker? It's only available in the LS2/LQ9 (the 364cid block). With that being said, it's got a different crank clearance for the pistons and is not interchangeable with the LS1/LS6 block. So I'm stuck with so many options, 383, 393, 377... but I don't want those setups.

The 408 has a bore of 4.030, a stroke of 4.100 and a rod length of 4.125, correct? Those are the numbers I got from Eagle anyways. Does anyone else offer a stroker kit for the 408 and maybe a trusting setup, before I got out and spend nearly $3k for something that won't even work? I NEED HELP! Please, someone point me in the right direction. I'll worry about the heads/cam setup later, I'm just stuck with the bottom end worrying me now. If ya'll wanna chip in any info/advice on the top end, that'd be great too. Thanks for the help guys

~Jonny

 

Jonny,

Here are a couple of rules for you........

1. Block Bore Diameters....

You can bore/hone these out to .005" more, some of them go to .020" larger

LS1 = 3.900"
LS2 = 4.000"
L92 = 4.065"
LS7 = 4.125"

Now this block can go to .060" over if you want to push it but .030" is common

Iron 6.0L Block = 4.000"

2. Strokes

Stock Stroke for LS1, LS2, L92 and Truck Motors = 3.622"
Stock Stroke for LS7 = 4.0"

Aftermarket Stroker Cranks = 3.900", 4.000", 4.100"

3. Rods

Almost all cranks for LS1's need 6.125" rods at the minimum. Stock cranks use 6.098" rods from the factory but they are usually reaplaced with a 6.125" aftermarket rods. When you increase the stroke the counterweights will get in the way so the piston design has to go with the crank and rod combination. You really can't put much more than a 6.200" Rod in with a 4.000" stroke crank, or a 6.125" Rod with a 4.100" stroke crank.

3. Math

To find displacement :

Bore x Bore x Stroke x 8 x .7854

This will help you figure out what you are looking for.

5. PISTONS:

Compression Height, this is the key to getting a piston correct for your setup.

To find what compression height piston you need for a LS motor:

9.240" - (Stroke/2) - Rod Length = Compression Height

or

Compression Height + (Stroke/2) + Rod Length = 9.240" (Deck Height)

Not going to hand feed you the answer when I could type this and you can figure out everything you need to know.

Bret

 

Jonny, you aren't going to bore/hone the LS1 to any more than around .010-.020 (.005-.008 with a 97/98 block), so the max you'll really want to go with without compromising the block integrity is a 383.

For a big displacement motor like you're talking about, you'll either need to go with a wet-sleeved LS1 ($$$$$), a 364ci LS2, or a 364ci LQ4/LQ9 block.

Mike

 

Jonny,

FWIW I'm doing a 440cube LS2 motor now. Race Engine Development Sleeved LS1 Block with a 4.000" stroke crank. Coulda gone to a 450cube motor with a little more bore and a 4.100" crank but it wouldn't fit into some race classes so that idea was tossed out.

As Kraest said.... 383 is all you really get out of a LS1.

Bret