I know a few people have put the flat top 4.8 pistons on a 5.3 rods and crank, and I was wondering what all was needed to make it happen, also would the stock head gasket hold up to the higher compression? Also thinking about possible heads and cam, but I really don't want to sacrifce fuel economy (since its $5.00 plus a gallon in Canada for 87) any thoughts or insight would be much appreciated thanks.

Edit: I should mention I drive 350-400 miles a week and want to keep it NA

 

I did this on the 5.3 for my wifes suburban, had to go up the 93 octane. Mpg was not affected and the power is better.

 

I wouldn't expect this to work. I didn't think you could use pistons designed for a different stroke crank. It seems like at the top of the stroke the piston would be above the top of the block but I guess if it's been done then I'm wrong about that.

 

It does work, and it has been done alot. In fact, GM did it, and gave it RPO L33.

Stock head gaskets are fine. Build it, tune it, drive it. I put 12 psi to my L33 on 90 octane. Tuning will determine your fuel requirements, just have it tuned for the fuel that you want to run.

 

And GM does it in every RPO Code of 5.3 in the 2007+ GMT900 trucks as well. Connecting rod determines whether the pin height would work and the shorter stroke crank of the 4.8 uses different rods.

And I agree that tuning really is what determines octane tolerance to a certain extent. Static compression with the 61 cc heads with probably be in the 10.3:1 range ( versus the L33 or any other newer 5.3 that has 64 cc chambers that are 9.9:1). It probably would be happier on higher grade fuel.

 

Forget to mention mine was bored over due to cylinder rust, with the oversize I'm at 10.5:1

 

I was reading some where on here that there is different wrist pins, obviously they wouldn't work, was kind of wondering of the wrist pins would be the same from '99 to '06 ish?

 

That explains it.

 

The pins are not the same between years regardeing the 4.8/5.3 . There was a change made around 2005. Gm went from a press Pin to a floating pin.

 

I am really considering this on my DD. I drive 60+ miles each way to work and believe the higher CR would increase the thermal efficiency. What cam works good to bleed off some cylinder pressure at low speeds while spicing things up when you are up to speed?
anyone have real world scenarios to offer? what about converter stall on a daily driven street truck?
I appreciate any advice.