So the other day I was at the local Chevy Dealer's Parts Department waiting my turn in line and I picked up the new Silverado catalogue to pass the time. I noticed that the new 4.8 was rated at 295hp @ 5600rpm and 305lbft @ 4600 rpm. What did GM do to get that? That's at least 20 over both on my '05 4.8.

 

Probably some more factory fine tuning is my guess?

 

It went to 285hp in,I think,2003. It started out at 255hp in 99 then went to 270,285 and now 295.

I think it's mainly tuning,also.

 

295hp 4.8 came with the GMT900 in '07. That's what mine has. Probably tuning. Maybe heads or something too?

Mike

 

LS6 heads

 

Just curious, why do you list your dad's wrecked truck and your MOMS new car in your sig???
________
The Cliff Condo Pattaya

 

its the heads, the new 4.8 will runs with the old 5.3's stock

 

What's different about them,just larger valves?

 

Like said they switched to 243, gives a lil comp jump, they flow better.

John

 

I know the newer 4.8's and 5.3L's have been getting the 243's, but then what else changed? Bolting on a set of 243's with stock pistons would actually lose compression, since the 5.3L heads have smaller chambers than the 243's. So if compression is up, but 243's are on...what changed? What kind of pistons?