Building a 5.3 Can I use 317 6.0 heads on this small bore size or should I stay with the 798 5.3 heads???? Or can I use 243 heads??

 

I would say no on the 6L heads . The 243's will work but You'll end up with a little lower compression ratio. Are You rebuilding the engine ? I would say use the 5.3L heads as of the heads You've mentioned the 5.3L heads have the smallest combustion chamber and will net You the higher compression ratio .

 

317's will give you crazy low compression, too low for most boost combos, and definitely too low for an NA or nitrous build. Some ported 5.3L or Ls6 heads would be a much better choice!

 

What do you guys have for a small chamber ported head? This is a aluminum 5.3 with factory coated flat tops going to run a perf cam and open carb intake and carb.

 

We have both the ported 5.3L heads and ported LS6 heads that would fit the bill and be relatively easy on the budget!

 

Not sure what heads your talking about, do you mean 799 heads. What year is the 5.3. What is the 8th digit of vin #

 

I imagine He's talking either 862's or 706's .

 

Well that would be my guess too but, he said its a aluminum block ! So if its GEN III it could be a LM4 or L33. If its L33 it could already have 799s. This is why I asked for year and vin to ID

 

Don't have a vin number bought this block from a guy that he thought it came out of a ssr. because it has coated gm flat top pistons.

 

Are You sure it's not a 4.8L ? ,,,,,,,,,,,,same bore and all the 4.8L's use flat-tops The only way to tell without vin information and it being aluminum block and all is to measure the stroke .

 

Have you ever seen an aluminum 4.8? My guess is it's an l33 with the 799's. If it has the 799's, keep them. They are the same as the ls6 heads with different valves. Send them to advanced inductions for porting and you will have a killer set of heads.

 

You guys are killing me! If in fact it is out of a SSR its a LM4 5.3 code SXV .The 2003 -04 got the LM4 , 2005 and later got LS2 . Side note only 3416 SSRs were built MY 2003.

 

I'd be willing to bet that you have a L33 with 799 heads. 799 is just a different casting # with the same specs as the 243. Stick with what's on the engine and add a cam to take advantage of the flow numbers. To answer the original question... 317 heads will kill your power for n/a due to the lower compression ratio. If you're going blow, then trade the engine for a LQ4 or something with dished pistons and a lower c/r from the start.

 

Yea it's a 9.9:1 L33...good platform due to the low weight...just cam it if you need more than 315hp..

 

Lol... who really needs more than 300 HP? We all just crave it.

 

Well just so you guys know this is going in a boat it is going to need all the help it can get. I have decided to go with ported 243 heads. Undecided on what cam yet because this is a carbed set up.

 

That changes almost everything... for a boat I'd go for torque not HP. The 243 heads will need to be decked ~.030 to retain your c/r, but I think you're going about it wrong. If it were me I'd go with some PRC Stage 2.5 5.3 heads, a .040 head gasket and a cam like a 210/218 high lift with a 113 + 4. That'll give you tons of power for pulling skiers and will do pretty well up high.

 

A boat like a boat? Or a huge vehicle like boat?

 

Boat like pontoon boat not looking for low end power because using a transmission, this is set up for top end speed for pontoon racing.

 

Are other boat has a ls3, cam, ported heads and does a 100mph + if you have the ***** to hang on.