I have an '07 Classic 5.3L Flex-fuel with ported manifolds, Corsa cat-back, AEM CAI, Factory e-fans, and tuned with 3.23s and Silverado SS wheels. A stall converter is not an option and must retain the mpg I'm getting. I have a friend with an LS2 TB SS. He is looking at a cam and heads for it. However, I could get the LS2 (204/211) cam and heads. I know the heads flow better but the combustion chambers are bigger thus my compression would go down so I would have to mill the heads to keep compression up. Probably mill them down to 58cc to bump the compression up to roughly 9.75:1. What can I expect to see in the powerband and overall gain in hp/torque from this? I wouldn't expect mpg to suffer much since I'm keeping the cam small.

Thanks!

 

Man, seems like a lot of work and money for such small gains

 

20 RWHP, I wouldn't be surprised.

You would be faster with gears, that thing must suck to drive with 3.23s. 3.90s would probably make your gas mileage improve if anything, expecially with those wheels. Just because your engine will be turning more RPMs doesn't mean mileage will suffer. If an engine is being lugged like yours is it has to work to get into an RPM range that will make some power, which wastes fuel uneccessarily.

 

My 05 RST came stock with 3:73s and believe it or not but with running 20" rims, the gas milage got better when i went to 4:10s. The motor didnt lug as much and no longer downshifted when the cruise is set.

 

Thanks guys with the input but gears are staying for a while...knocking out 21mpg going to work city driving and 24 mpg on the hwy so....can't complain with that.
....hand calculated...no DIC crap.

Thats what I was thinking....it wouldn't be much....I'll save the money for my project truck then.

Thanks.

 

Not really concerned about being faster...if I did, I'd go TVS or 6.0L....just trying to make my daily driver a bit more enjoyable withotu spending a ton of money since I have a project truck that takes all of it anyways.

 

Those are some impressive fuel economy numbers. Sounds like the 3.23s have there place.

 

Yeah, I'd have to admit...I'm impressed with the 3.23s with the 275/55R20 tire. It does struggle a bit down low around 1200-1600rpms but other than that...it moves along pretty well....similiar to my 2002 I had that was a Z71 and 3.73 gears.

All my mods are Corsa Cat-back, AEM CAI, throttle body bypass, factory e-fans, billet servos, and the Big 3. The Big 3 did help with fuel economy as well. I'm also running non-ethonal Marine Gas that's 89 octane which gave me another 1 mpg.

I'll be doing gears though....my 1990 has 3.73s and I'm going 4.10s in it and I'm going to take my 3.73s and put them in my 2007 since the gear sets are interchangable with the proper bearings.

 

21 is pretty good. Here are some of my numbers from back in the day... I don't calculate it anymore lmao

Pretty similar setups. Mine was STOCK 06 ccsb 5.3/60e/ 3.73's and ss 20's on 275/55's (magnaflow/cai only)

 

damn now that's getting dirty with the fuel mileage nice setup though haven't seen anybody do it like that before and thats funny u see a 15 dollar rise in gas from feb to june for the same 18 gallons