Just wondering what they'll take before I should be concerned. I know the L31 is stronger, but that needs a rebuild so it'll sacrifice its heads to my L05 for now. That with my 454TB, longtubes I have yet to buy, the LT-1 cam I do have, and the intake mani I need to buy oughtta put me around 300ish flywheel hp. I started thinking about spray and got to wondering just how much the L05 and L31 will take without getting forged internals. It's in a truck, and will be used as such, but I don't want to throw a 100 shot at it and find out on my first run that the motor won't take it. This is all assuming a good tune of course.

 

The L31 used the LT1 powdered-metal connecting rods, which are a fair bit stronger than the normal forged rod. They are typically good for about 400hp or so, more with good bolts like ARP. The crank will likely be just a cast crank, though some of the heavier 1-ton vans and the like might have a steel crank. Don't get your hopes up though. The pistons are hypers if they are the original ones, like the LT1 had but they are not the 'lightweight' versions that the LT1 had.

The block isn't anything particularly special - same sorta deal as the L05 and L98 blocks. Its a roller block, and should have all the roller cam machining already done, as the L31s did use a roller cam. Its also a 1pc rear seal block. May or may not have 4 bolt mains, depending on what it was originally put into, but like the forged crank, don't get your hopes up. 4-bolt mains isn't really a bit deal anyway, 2-bolt is pretty much just as strong.

If you are planning a mild engine like only 300hp at the flywheel, then you can use a factory shortblock without any issues. Its basically the same bottom end that the LT1 had (minus the 'lightweight' pistons) and those made between 275-330hp in factory trim, depending on vehicle and year. 300 crank HP is no problem for the L31 shortblock.

I wouldn't recommend N2O shot bigger than about a 125hp on hyper pistons though, as they are have a hardened face thats very sensitive to detonation, and can crack. Cast or forged would be better for N2O IMO.