i know that gas mileage isn't really the focus when getting a bigger engine but since its my daily driver also it helps to know around what mpg i will get..im getting the patriot performance 383 with 450 HP and torque with a turbo 350 trans and "high" 2.53 gears...can anybody give me an estimate on the mileage i will get?

 

does 10-15 sound about right?

 

Holy crap...2.53s are insane! O_o

Around town, 15 would probably be a pretty good estimate.

On the highway though, without an OD tranny, you'll be turning around (depending on tire height) 2200-2500 rpms. If it's near the high side of that, you'll be seeing some pretty low highway numbers...

 

yeah i know..i want to get 3.42's but that will have to wait for a little..well i get around 20mpg now on the freeway at around 2000rpm with my 305..wouldn't it be around 10-15 on the freeway with that 383?

 

here are the engine specs:

# Technical SpecsSeasoned GM 4-bolt Main Short Block
# 1-piece Rear Main Seal
# Patriot Performance Freedom Series Straight Plug 190cc Heads
# 2.02" Intake/1.60" Exhaust Stainless Valves
# Scat Crank and I-Beam Connecting Rods
# Clevite Bearings
# Hypereutectic Flat Top Pistons
# 10.4:1 Compression Ratio
# Fel-Pro Head Gaskets
# New Head Bolts and Hardened Washers
# MSD Street Fire HEI Distributor with 50,000 Volt Coil
# Aluminum High Volume Water Pump
# Edelbrock Air-Gap Intake (port matched to heads)
# Double Roller Timing Chain
# Polished Aluminum Valve Covers w/breathers
# Steel Roller Tip Rockers
# Hardened Pushrods
# Howards Hydraulic Roller Camshaft
# Cam Specs: 230/230 .480"/.480" 110LSA
# Mellings Oil Pump

along with turbo 350 trans, 2.5 gears, weight:3300lbs and i will use a demon carb

 

I think the 15 part of 10-15 is wishful thinking. I would guess 8-13. as a little closer but it all depends on how you drive it. If your the kind of guy that costs down hills and is light on the throttle all the time you might hit 15. But if your the kind of guy that sees a row of stop light as a lot of fun your going to be a lot closer to the 8. I had a 72 with a 350 3 speed auto I think I got around 11 MPG. That 383 will be a monster and it will need fed. Good luck

 

^ That's true. I tend to tell people a little high, since it's how I drive. I basically went by how I think I'd do. :P haha

 

The engine specs are almost identical to mine except I have 10.6:1 comp and a Crane cam with 234/244 dur and 488/510 lift. The rear gears are 3.43:1. I am running an Air Gap manifold with a Holley 700. Gas mileage with 30% 110 octane in the tank is only 8 mpg, but I have never driven it "nice" to see what is possible.

 

well now i have stock rear gears but im going to run those gears too eventually..what tranny do you have? i think im gonna run a Holly 600-650 carb...what would it be with just normal premium gas? is that 8 city or highway?

 

it would be nice to squeeze out atleast 15mpg highway with my new engine