243's on a 5.3 from the factory?
Thread Starter
TECH Enthusiast
iTrader: (16)
Joined: Jun 2004
Posts: 586
Likes: 0
From: Farmingville, New York
243's on a 5.3 from the factory? Not really an important, but I picked up a new 2008 Avalanche in December taking advantage of GM's Red Tag event. Anyway, I was under the hood doing it's first oil change and I noticed that it has 243 heads on it from the factory. It's the 5.3 with "Active Fuel Management" and it's 2wd which is rated at 320hp as opposed to 315hp for the 4wd. I thought the 5.3's had different heads with smaller valves and chambers? Anyone else ever notice this?
Yep, The 07+ Gen IV 5.3's will have either a #243 or #799 casting. Both are the same port, flow, etc... Just different castings. Most of the reason for the 07+ HP and TQ increase over the #853 castings.
Mine has the #799's and runs pretty nice for a stock truck.
Mine has the #799's and runs pretty nice for a stock truck.
Trending Topics
Some 06 models got them too! mostly 799 from what I have seen. But The Vette or GTO's W/LS2 are the only ones that got the Hollow stem sodium filled valves. Same combustion chamber and valve size though
LS1 Tech Stories
The Best V8 Stories One Small Block at Time
6 Common C5 Corvette Failures and What's Involved In Repairing Them
Pouria Savadkouei
Retro Modern Bandit Pontiac Trans AM Comes With Burt Reynolds' Autograph
Verdad Gallardo
Top 10 Greatest Cadillac V Series Performance Models Ever, Ranked
Pouria Savadkouei
Top 10 Most Powerful Chevy Trucks Ever Made!
Hennessey's New Supercharged Silverado ZR2 Has 700 HP
Verdad Gallardo
Coachbuilt N2A Anteros Is an LS2-Powered C6 Corvette In Italian Clothes
Verdad Gallardo
Awesome K5 Blazer Restomod Comes With C7 Corvette Power
Verdad Gallardo
10 Camaros You Should Never Buy
10 LS Engine Myths That Refuse to Die
Verdad Gallardo
They are the same 64 cc chambers, and the same 2.00 intake and 1.55 exhaust valves as the vette 243s. Everything is identical to them except that the valves are solid and not sodium filled. I just bought a 2007 engine and sold the heads on it so i had to take measurements and such to be certain. I didnt measure the cc volume but i know they are.
