blackbyrd

iTrader: (10)

I know it's been asked a million times, but I've got an odd case.

Recently bought an 06 ext cab, it came from a tow recovery lot so I don't have a whole lot of history. Before I got it the guy put a transmission in it. Odometer says 166k vin says 4.8, airbox says 4.8 spid sticker says 4.8. I had a 5.3 ext cab many years ago (04) I bought new with and It feels like a 5.3 I know seat of pants dyno is subjective. The engine bay was super duper cleaned and so was the engine. Truck has a few other mods to it that makes me think someone may have swapped.

Is there another way to tell besides the vehicle identifiers with out me looking at pistons or taking the accessories off to look at the block.

shakenfake

You'd need to pull the heads. Maybe could pull the oil pan and measure the rods

strutaeng

Remove a spark plug and boroscope to see if dished (5.3) vs flat top (4.8) pistons?

I think there was a 5.3 that did have flat top pistons though, but I think that was an aluminum block?

blackbyrd

iTrader: (10)

Yeah I've read that one isn't consistent, then something about the vally cover being flat but that maybe on about new 4.8s without afm.

Looking for something simple like casting numbers haha.

I also considered hooking my hptuners up to it to look at the tune. You have to calculate volumetric efficiency and divided it by 8. It should be a different value there between the 4.8 and 5.3. Just not sure if have to have credits just to look at the tune or not.

RB04Av

Borescope tells all. An incredibly useful tool overall, kinda like a multimeter and an infrared thermometer. Get yourself one (maybe $15 or so) and hook it up to your phone, you won't believe how many things you can find to use it for.

5.3 is dished except for the L33 A F A I K, which is the one strutaeng referred to; 4.8 is flat tops.

The same block castings are used for both motors. No help there.

_zebra

iTrader: (5)

the L33 5.3s used flat tops to account for having 799 heads (plus the aluminum block is also a dead ringer)

but then again... if this truck has other mods indicative of somebody knowing more than how to change the blinker fluid, it's still anybody's guess. you can change heads like your underwear. changing rotating assemblies is obviously more of a chore but not unheard of.

best bet, though, is if it's got 706 (or 862) heads, and iron block, and flat top pistons - you're most likely looking at a 4.8

_zebra

iTrader: (5)

jack it up & spin the driveshaft... how many turns does it take for one axle rotation?

shakenfake

Didn't even think about the boroscope.

Yes the valley cover is only flat if it is a Gen IV. Gen III is the same across the board.

joom

Lm4 was an aluminum head gen 3 motor with 862 or 706 heads also .

joom

Ok I have to hear this .