to carb or not to carb?

[mister.freeze]

OK, I've had Holley's ProJection 2d TBI for the better part of 10 years on the Fox's 383 stroker. I've run it in both big an small block mode, with and without the closed-loop O2 sensor. I just feel that I've never gotten the best out of the stroker. The mpg has settled in at about 9.16, with or without tail/headwind, up/downhill, trailer or not, top on/off. ANYBODY have an idea what cfm a motor like that needs? The ProJection is rated at 650. It's been VERY reliable and works well, but I know there's more to be had out of my motor, especially in the mpg department. Should I carb? Go propane? Leave it alone? I'd LOVE to go diesel...

[72cheyennesuper20]

I'd love for you to put a Duramax in your truck so I could follow the build and do it to my truck. I am suprised that youi are not happy with the projection, I wanted to do it to my truck. But maybe not now.

[ClassicJimmy]

I was thinking of going that route too. Does anyone have a 383 stroker carbed, what carb, & what's your average mpg? I'd like to build mine as a daily driver, but I need to have decent mpgs at todays prices or I'll have to get a second job to pay for gas! I thought diesel was the way to go, but now diesel is almost a dollar more than regular - go figure! Propane might be the way to go - does anyone have that setup? I'm interested to hear what you fellas have to say!

[vtblazer]

If your looking for mileage, install an older style 6.2 diesel, their as close as you'll get to 'bolt in'.
You could average from high teens to better than 20mpg with one with the right gearing.

I'm currently running an injected 383 myself but it's not in a driver per say, so I have no idea of the fuel mileage.
It is in my off road ride and it runs very sweet with tons of power on demand.

The difference from your set up is that I'm running a chevy TBI that's been chipped, otherwise stock.
I think a larger throttle body would improve performance, so might larger injectors over 4000rpm but currently it runs good enough.

As for mileage in these beast's, remember your pushing a brick through the wind and that getting better fuel mileage is more a function of having an over drive transmission than having injection on the motor.

[mister.freeze]

don't get me wrong; I've been very satisfied with the ProJection. I just don't think the programmed maps are optimal for a 383 stroker. Other things come into play to: I've got 10.21:1 compression and I have to WAY retard the timing for daily use. I do have a 700r4, and a torque converter lock, but none of that has helped in the MPG. I built it because of the speeding brick effect, thinking more horses would work less hard and sip rather than gulp fuel. I'd like to try a carb, but finding a loaner is dicey. My Projection may end up on a shelf soon one way or another...

[Critter]

Originally Posted by mister.freeze

don't get me wrong; I've been very satisfied with the ProJection. I just don't think the programmed maps are optimal for a 383 stroker. Other things come into play to: I've got 10.21:1 compression and I have to WAY retard the timing for daily use. I do have a 700r4, and a torque converter lock, but none of that has helped in the MPG. I built it because of the speeding brick effect, thinking more horses would work less hard and sip rather than gulp fuel. I'd like to try a carb, but finding a loaner is dicey. My Projection may end up on a shelf soon one way or another...

Just curious, what gears and tire size are you running?

[mister.freeze]

3.73 gears and 33x12.5's.

[vtblazer]

IMO, it's the motor.
Being built for power, not fuel economy.

Does seem like it could be better with that gear/tire/ combo though.

[Jtrux]

I don't think mileage will ever get any better, however, you might be able to eek out some more power with a carb if your having trouble with adjustability right now. It seems to me though that keeping with the FI would be the best bet. Have you called holley to get there input??