I picked up a 5.3 long block for a decent price after I found a crack in my LS1 block. So now I have a complete 5.7L rotating assembly and a good 5.3L long block. I'm looking to build a decent running street engine for my 63 Impala. I plan on using fuel injection with a factory LS1 intake. Any suggestions on which way to go with this?

 

The two things I can think of are: (1) use the 5.3 block and build a 5.3 engine or (2) bore out the 5.3 block to LS1 size and use your good LS1 rotating assembly.

 

Would the stock LS1 pistons and rods be worth using? I'd like to be able to add a single turbo on it later on. Is there a difference in the cc of 5.3L heads and 5.7L to produce an acceptable CR for 8-10lbs of boost?

 

The LS1 rotating assembly is pretty tough, although I would get ARP rod bolts. I would have no problem using the crank and rods for boost. You might consider forged pistons though. Then you could get ones with valve reliefs or a dish. As for combustion chambers, the 5.3 heads are 61cc and the LS1 heads are 66-67cc. I would not use either though. At least get 243 heads (LS6) which are 64cc.

 

I would definitely get forged pistons. Do it right the first time. Yes theres people pushing the limits of stock internals but they do so knowing they can lose an engine.

 

The pistons seem to be the weakest link in the LS motors from what I've read about them. I think that's the way I'm going to go with this. Might as well get the most out of what I have. At least I have the broken aluminum block to mock everything up with in the car, so that thing can still be somewhat useful.

 

First things first if you are even thinking about building a 5.7 out of it you have got to get the bare block over to a machine well equipped machine shop and figure out if the bore is thick enough to bore it that far. Most are, but I would definately spend the money and make sure it would be ok to bore that far before I bought a single part to build it. It would suck to have the machinist punch through a unknowingly thin wall. It would suck even worse to have a really thin wall and have it collapse/buckle and punch a piston through everything ruining the whole motor.

 

The easiest route might be to leave the 5.3 as is and get a set of 317 heads. They have the 243 ports but a 72cc chamber to lower the compression to 9.5. With 8-10 lbs. of boost on the street you'll be safe. Something to consider!! Larry.

 

A 5.3 short block with 61cc 5.3 heads is about 9.5 CR already. If he put 71cc 6.0 heads on he'd be around 8.5 CR.

 

Have the bore sonic checked as kossuth suggested and go LS1 bore. Don't use the used LS1 pistons on the fresh bore. Go forged pistons, have the rods resized with ARP bolts, the crank freshened and 72 cc heads. Then go ten pounds without worries. I personally hate to skimp on the bottom end. Just too much work to correct a big bang.

 

If on a budget bore the 5.3 to stock ls1 spec and get some new rings and you are good to go. Since 5.3 and 5.7 are the same crank I would use the better condition of the two.

 

If going turbo later then just pimp out the 5.3 block and use that. It has been shown that 4.8s and 5.3s do well with boost.

By pimping it out I mean rod bolts, head bolts, head gaskets, cam, valvetrain etc.

 

True. Aren't some 5.3 production years made better than others? Example, thicker cylinder walls.

 

That's probably the way I'm leaning on this project. I was looking at using the LS1 pistons because I read they are hyper pistons over the 5.3Ls cast pistons. Plus I wouldn't have to balance the assembly. I agree that doing it right the first time is the best, so I'll probably go with forged LS1 pistons if the iron block can handle the bore. Does anybody have an opinion on the Diamond or Probe pistons? I saw several people in the turbo Buick world steer away from Diamonds because of their lack of material between top ring and piston dish causing failure. Has anyone experienced those problems in the gen III Chevy world?

 

I'd probably get Wiseco pistons from Texas Speed.

While having the cylinder walls sonic check is a good idea, the 5.3 block is plenty meaty and almost always will take an overbore to LS1 size. Core shift that was fairly common with the old school small blocks is virtually a thing of the past.

 

No disrespect, but you are dead wrong. Did GM leave a lot of extra meat in most of these motors? Yes, and lucky for us that many of these 5.3 blocks are suitable to bore from a 3.78" to a 3.898", but you have to remember you are taking almost .120" of of each cylinder. That's a lot of material. Here are the results of a 5.3 block I had scanned with the intention of boring to a 5.7. As you can see there are areas that were plenty thick, and there were some that would have only had about .100" of cylinder left on the thrust side if it would have been bored over. Not checking is taking a very expensive chance.

 

Here is some good reading on sonic checking. They mention .140" as getting alittle thin. My machinist that checked the motor was comfortable going as thin as .125" being I wasnt boosting or spraying it, but I wasn't even close to that. http://www.popularhotrodding.com/tec...s/viewall.html

 

I said most were thick enough. You showed one example. Show me a hundred blocks with the majority failing. But yeah, I would not bore that block out .125". Again, it's a good idea to have the block sonic tested.

 

Why bother doing anything with the ls1 motor. They are usually easy to sell. Sell it, use that money to build the 5.3. Heads and cam alone will make 500 crank on a 5.3. Then add boost down the road.

 

I would love to sell it. It's a decent block, except for one of the rear most head bolts broke out a chunk of aluminum in the bell housing area.