1QWKT/A

iTrader: (2)

So I built my car at a time when I had a DD. Gas mileage was of no concern. It's a 383 with a pretty aggressive cam and AI ported stock castings that made 430 on a dynojet. I can give more specifics if that would help. Long story short; I want to hit 17-18 mpg on the highway if that's anywhere in the realm of possibility. Wondering what stall and gear combo would be the best?

Right now it is 3.73 gears with a 2800 (I think) Fuddle. Any tips or tricks would be great. Maybe aftermarket EFI? Never tried to build a car for efficiency so I'm kind of lost.

1QWKT/A

iTrader: (2)

234/242 109+4
.565/.565 Lift w/1.6 Rocker

Cam Specs

190 CC CNC Job from AI

bowtienut

iTrader: (1)

There's no reason you can't get 17-18 with those 3.73's. And the converter, being locked, will have no effect on highway mileage. 2800 stall is low enough that it will even have minimal impact in city driving.
Throwing money at it will not help get you more fuel mileage. Forget the aftermarket EFI; the GM PCM is as good as it gets for what you want.
Any decent mail order tune should get you there.
Of course I'm assuming we're talking about an LT1 here. What year? (S/D or MAF).

Edit: Just saw your 2nd post. There's quite a bit of overlap with that cam, so I can see the possibility of the PCM dumping extra fuel in at idle/low speed based on O2 voltages. If so, any good tuner should be able to account for that.

1QWKT/A

iTrader: (2)

93. I've only been getting 15-16 highway. Maybe a little more tuning is in order. Alvin at PCMforless had it a few years ago. There was a coolant leak so he couldn't run it for as long as he wanted to get it completely dialed in.

The car has been sitting for a year while I'm out of the country so I haven't gotten the chance to mess with it in a while.


I also remember him telling me something about a lock-up solenoid on my car possibly being bad. I thought the converter used a clutch system? Any chance that is my problem?

1QWKT/A

iTrader: (2)

Now that you mention it there is just a tinge of the smell of gas at idle. Maybe it's a bit too rich. The Arizona Speed and Marine Monoblade was also giving him trouble getting the idle right.

95mysticta

iTrader: (4)

As bowtienut posted you should be able to attain that mileage. Stalled autos generally suck alot of fuel and mated with 3.73s spinning high on the hwy its not a recipe for getting good mileage. A monoblade is also a pain to tune with and a 58mm is more better suited but if you can get around it then keep it but just makes things easier. Do the basics new O2s, clean maf, and a good retune to even out the a/f. Just some suggestions.

Zebisko

iTrader: (3)

The torque converter had a clutch in it that is actuated by hydraulic pressure that is activated through the lock-up solenoid. If the solenoid is bad, it will not send pressure to the clutch causing the torque converter to never lock.

1ltcap

i'd say leave it as it is, and go pick up a $500 POS for a daily driver.

speed_demon24

iTrader: (6)

Put 3.23's back in it. I've gotten 25-26 with cruise set at 80-90 with my setup back when i had 3.73's. I still haven't gotten around to getting the speedo corrected with the 4.10's yet so I don't know how much it affected my millage.

1QWKT/A

iTrader: (2)

Thanks for the help so far guys. The solenoid is definitely bad. It was blowing a fuse everytime it engaged so it is unplugged. Would the converter not locking up make the mileage that bad?

93 LT1 Vette

Better gears will help and a tune with more timing. But the biggest savings is your right foot. You could buy a vacuum gauge and just keep it off of zero. Mount it on the hood and just tell everyone your running boost. LOL, but with that cam and gears your limited.

Zebisko

iTrader: (3)

If I remember correctly, a lockup converter on a stock car is about a 10 percent increase in efficiency. My assumption is that the stall would make that increase higher.

ahritchie

iTrader: (1)

6spd trans swap....way more fun to drive and efficient!

96capricemgr

iTrader: (1)

Get the lockup fixed and a good tune, maybe look into the heated O2 conversion.

Someone said clean the MAF which would be a good idea if you had one but you said it is a 1993 right?

With a good tune and lockup you should have no problem with your mileage goals.

Putting a 58mm on instead of a monoblade would mean swapping the intake as well to put one back on with an intact IAC distribution circuit. Probably more than you want to go through and would take a LONG LONG time to recoup the cost in fuel savings. I do think the IAC circuit working right would help fuel savings a little though.