I'm looking for a used short block for a low budget project. I thought maybe a L31 350 out of 96-99 truck or van would fit the bill.

I like the fact that it has a 9.4:1 CR with 64cc heads.

After some searching I found some negative comments about the L31 having a loose bottom end.

Should I avoid buying a used L31?

 

maybe maybe not, lot would depend on what sort of project you're going to use it for. it'd help out if you took the time to say whta the intended usage was goign to be, and your budget.

 

The budget for the short block is $500-600. The goal is 340-350hp.

I'm looking for a used roller short block that will result in approximately 9.5:1 compression when using 64cc heads with a 0.028" head gasket.

The L98 meets all the criterea but seems to be more expensive and less availible.

The truck L05 has less compression if I'm not mistaken. (8.9:1)

I am just curious if the L31 has a history of bearing or lowerend trouble. If it does, I may have to opt for a short block that will result in less compression.

 

The truck L05 is crap. I wouldn't go there.

If the short block's tightness or whatever is of concern to you, take it apart after you buy it, and mic it. Get the crank turned and put new bearings in it if you don't like what you see. That's about $150-200 to guarantee that it's the way you want it... something I would do (and in fact have done) with any junkyard motor I bought, no matter what it was. Cheap insurance.

 

I thought the L31 was a 5.3L (327ci) and not a 5.7L (350)?

And its based on the LS1 block, only iron cast, isn't it?
I could be wrong here, don't know much about the L31's, but I might be right.

 

(you knew this was coming) Why is the truck L05 short block crap? The only thing I can think of is the dish pistons they use. Well, the heads are no good for performance but I won't be using them.


Sounds like good advise. I am just hoping to raise the odds of finding a short block that is in spec by not buying something that is known to have problems.

 

http://media.gm.com/division/chevrol...an/subeng1.htm

 

The heads. There's nothing wrong with the short block itself, it's just a bunch of cast stock pistons and stock rods and a cast crank and a block. No better or worse particularly than the L31 except that the L31 supposedly has a roller cam which the L05 doesn't.

I thought for some reason that you were looking for the Vortec heads. Othere than that, there's not much different about it from any other roller-block 350. The L98 and L31 short blocks aren't significantly different.

As cheap as it is to repair or replace those parts while you have one sitting on the floor, any kind of anecdotal "history" of some kind of short block problems is not something that I would be too concerned about. Especially since it's in one's best interest to go through those exercises anyway, just so you have a more nearly new engine rather than a used one.

 

Well if you want about 350HP the easiest route would be an L31 motor. With the vortec heads you could make an easy 350-400HP just by changing the cam and putting some decent induction on it.

 

I know of no reliability issues with the L31. I have a 99 Tahoe with 79,000 miles on it. Alot of those miles are pulling a 7,000 pound trailer at 4200 rpm's going up some of the hills we have around here. I would have no problem putting a used L31 in anything. I would pull the pan and heads first.

Just my opinion,
Mark

 

My block came from a 97 chevy truck. It's the vortec block, 1 piece rear, roller, 4 bolt main, ........ it's a nice block to use.

 

1bad91Z,

Did your L31 come with the stock pistons? Were they flat top, or dish?