So I have a 5.3 from my 2003 express van that was wrecked and I want to do a rebuild with some upgrades and drop it in my 99 Silverado that has a stock 4.8. I'm wondering other then the rebuild what kind of things should I add for a motor that needs low end torque (1000-3000 rpm) and won't likley ever see over 5k rpms?

 

Small cam and lightly ported/milled heads will get you some nice torque.

 

Any suggestions on what heads to run? The heads that are on the 5.3 currently are stamped 862 on the passenger side head near the valve cover up front. Silverado 4.8 is the same 862.

 

If you plan on boring out the block go with a flat top piston. That will give you a bump in compression to the 10:1 depending on head and gasket. Some more torque for ya.

 

Need to run 91 octane with 10:1?

 

Yes but more compression more torque, you should go even higher than that.

 

^^^^

 

Higher then 91 octane is not really an option for me. All my local gas stations have 91 that's it. And I live in the boonies so getting higher octane requires driving 30 mins over by the local fair grounds to get up to 107.

 

I'm sure he meant higher than 10:1, not higher octane. Id try to get around 10.7 or so on the compression.

 

Yeah but you can even go higher than that. I mean engines like LS2s and LS7s are pushing 11:1 comp and run just fine on 91 octane. It's all in the tune.

 

Sorry, I can see now rereading that post was confusing. 91 pump gas will be just fine, that's all I can get out west as well. Just have the tune touched up when the project is over and you'll be just fine.

 

Oh ok. I was a bit confused there. What compression ratio is acceptable on 91 octane? And any ideas on heads? Info in post #3. Thanks guys. Hope to get the ball rolling here pretty soon. My 4.8 is getting tired at 250k and lets face it, it's a stock 4.8.

 

What's the price u willing to spend

 

On heads? I'd like to just use a stock casting and have some porting and possibly some milling.

On the rebuild? I'd like to keep it around 1000-1500 all done.

 

What is the engine code in the glove box on your 2003 express van? Dont get your hopes up yet, as it is more than likely a 4.8. Let us know.

 

I'm just doing a simple 5.3 rebuild... Stock rebuild with ls9 head gaskets, Ls6 cam, ls1 intake and ported 862 heads, might even put a snail on it..

 

I appreciate the concern. But it is a 5.3 I bought the van brand new in March of 2003. Had it ever since. And just fyi express vans don't have glove boxes.

If I was just going to do a stock rebuild I would just start with a 6.0. I don't think I can do an intake swap or a "snail" (never heard that before, took me a minute) due to CA Smog crap. Thats why I was looking for minor internal mods.

 

Flat top pistons will not make a 5.3 with 862 heads 10:1 compression. It will be closer to 10.5:1

For what you're doing I would get a mild cam, Clean up the heads in the bowl area and proceed with a basic rebuild.

You can gain some compression by milling the heads and going with a thinner head gasket. Example go to a .040 head gasket and mill the heads to 58 cc's Will get you just a hair over 10:1

You really need to know how far the pistons are above the deck though as you don't want to tighten the quench too much.

 

Thanks for the good info. Sounds like a good option.