I’m building my first LS style engine and I was wondering what is the max stroke you can run on a gen 3 block without having to clearance the block.

 

The 4" stroke is the size most used. Any other size would be far less common. You would need to clearance the block with a 4" stroke. Any longer than that, and you might run into other issues. The 3.9" stroke is about the only other size smaller than 4". It would be more difficult to find, but I know K1 makes one. The biggest problem you will have with the 3.9" stroke, is finding pistons. There are some, but not many pistons available for the 3.9" stroke.

 

Around 10 years back, or more, Scoggin Dickey had a 4.100 stroke crank made up just for them, made by Callies. They claimed it reduced oil consumption issues that the 4.125" stroke created. They may still sell it, idk.......

 

This is a very interesting conversation. I've wondered about this myself as I"m doing cam and full exhaust on my 2500HD LQ4 and wonder out loud what would happen if I blow it up LOL. I would likely go with a larger cubic inch stroker motor. I also stumbled across the Ohio Crankshaft website and man do they have some extremely competitive prices.

https://ohiocrank.com/short-blocks/

$3,495 for a 383 is about as cheap as it gets. It got me wondering what block they are using and if someone could call and get a LQ4/9 based 408 for the same price.

$5,995 for a dart lsnext short block is stupid in 2024 too. They have longer sleeves that could easily get you into the 440,454,maybe even 468 range. Would be a NA torque monster with the proper cam, even with stock heads.

 

421's have been built from Gen III and Gen IV iron blocks but a 4" throw is about as much stroke as I'd want to go. The more throw you go the shorter that piston gets which means you'll be going back through that engine more often.

 

I agree on the 4" for being most reasonable. Even the 4" stroke, when combined with the OEM LS7 6.062 long rod, results in a marginal rod/stroke ratio of just 1.51. Thats mighty close to the OEM 400 SBC of 1.48, which many berated for pistons and cylinders not having a long life. Most engine builders dont like going below 1.5:1, for longevity reasons....

 

I have an LQ4 with a 4.1 stroke crank. It is bored .070 with 6.125 rod. It is a Callie’s crank. Weisco makes a piston for it. Block is half filled and was built by a professional engine builder. Poor mans 427

 

And my guess is that it never sees hot summer days with the A/C on or long periods of time at idle in a traffic jam with the windows down..