Awful gas milage.

[4WDKC]

Right now I see mid 14s, every now and then the afr dips up to 15, depends on my foot

Do you have a knock sensor?

 

[Matt69olds]

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The truck is a turbo 350 truck, but the trans was pulled from an 89 and I swapped it in. There is 0 wiring in the truck for lockup, but I pulled the pan before install and DID see the solenoid, just with 2 clipped wires... and the converter is the stock one so it should be lockup. I can just give that solenoid 12v and ground right?

Is there a chance that he built some of the internals to not handle lockup as well?

You can ground the black wire, and apply power to the red wire, that will lock the converter. The only issue is it will lock as soon as the trans shifts to 2nd gear. The best way to wire it is thru a normally open pressure switch. You may get lucky and your trans will already have one. If not, they aren’t expensive. Remove all the pressure switches, use some compressed air to blow into the end. Your looking for one that is has no continuity to ground with the switch unpressurized, and shows continuity to ground with pressure. Screw that into the 4th gear port on the valve body, cap off all the other ports with a 1/8 inch pipe plug. Connect the black wire to the pressure switch, the converter will lock once the trans shift to 4th gear. Wire the red wire thru the brake switch. Get a brake switch for a truck with cruise control. It will have 2 switches built in, with 2 pairs of contacts. One pair of contacts will be open with the switch button compressed, and then close with the switch at rest. Those contacts will be for the brake lights. The other pair should be closed with the switch button pressed, then go open with the switch released. Connect the other solenoid wire thru those contacts to a fused ignition on power source. Wiring it this way will automatically unlock the converter when you step on the brake pedal. Hope that helps

 

[Obwonkonobe]

Do you have a knock sensor?

No, the fi kit is basically a throttle body with an 02 sensor and temp sensor, everything else is built into the unit. Other than that it’s a carbed vortec 350

 

[Obwonkonobe]

You must be registered for see images attach

You can ground the black wire, and apply power to the red wire, that will lock the converter. The only issue is it will lock as soon as the trans shifts to 2nd gear. The best way to wire it is thru a normally open pressure switch. You may get lucky and your trans will already have one. If not, they aren’t expensive. Remove all the pressure switches, use some compressed air to blow into the end. Your looking for one that is has no continuity to ground with the switch unpressurized, and shows continuity to ground with pressure. Screw that into the 4th gear port on the valve body, cap off all the other ports with a 1/8 inch pipe plug. Connect the black wire to the pressure switch, the converter will lock once the trans shift to 4th gear. Wire the red wire thru the brake switch. Get a brake switch for a truck with cruise control. It will have 2 switches built in, with 2 pairs of contacts. One pair of contacts will be open with the switch button compressed, and then close with the switch at rest. Those contacts will be for the brake lights. The other pair should be closed with the switch button pressed, then go open with the switch released. Connect the other solenoid wire thru those contacts to a fused ignition on power source. Wiring it this way will automatically unlock the converter when you step on the brake pedal. Hope that helps

This is EXACTLY what I’ve been looking for, I should actually have everything I need besides the wires under the pan, so I’ll be going to a yard soon to grab those. Thanks a ton!

 

[Obwonkonobe]

ALSO, I absolutely SCORED yesterday, I bought an open 3.73 axle from a 77 for 150! I popped the cover to confirm and check out the gears, and everything looks healthy, it’ll get cleaned up and put in very soon

 

[4WDKC]

This is EXACTLY what I’ve been looking for, I should actually have everything I need besides the wires under the pan, so I’ll be going to a yard soon to grab those. Thanks a ton!

what do you have timing set at? Leaning it out with out a knock sensor can be expensive, the vortec heads are very efficient and make the most power at 32* timing. This may be the saving grace for you and trying to lean it out.

 

[Obwonkonobe]

what do you have timing set at? Leaning it out with out a knock sensor can be expensive, the vortec heads are very efficient and make the most power at 32* timing. This may be the saving grace for you and trying to lean it out.

I have initial at 14ish, but I’ve gotta put some tape on the balancer to find total

 

[Richard Schultz]

I have a 81 1500 4x4 chevy,350 3-08 gears,4 speed with a carb getting 15 mpg,running 31 10.50 15 tires.Summit has a wiring kit for your tranny to lock in the torque converter.In town just leave in drive,on the highway leave in drive,unless your on flat land,then you can use the od.In drive on the highway at 75 should be 2400 rpms.Try timing at 15 btdc.Make sure you use ac delco plugs,or rapid fire.

 

[Richard Schultz]

Also try running premium fuel to see if your mileage improve.

 

[Obwonkonobe]

Also try running premium fuel to see if your mileage improve.

Which do you run? And by drive do you mean 3rd gear? Because I drop it in 3rd on the highway and at 80 I run in the area of 2800 rpm, and it likes it a lot, I got a lockup kit today, hopefully that, my soon to come electric fan conversion, a shift kit, and my coming 3.73 instal will help a lot

 

[Obwonkonobe]

Also try running premium fuel to see if your mileage improve.

Which do you run? And by drive do you mean 3rd gear? Because I drop it in 3rd on the highway and at 80 I run in the area of 2800 rpm, and it likes it a lot, I got a lockup kit today, hopefully that, my soon to come electric fan conversion, a shift kit, and my coming 3.73 instal will help a lot

 

[Super-Dave]

Well, I see I am not the only person with this confusion.

I have a '74 with a .030 over 350 high nickel content block, full rebuild, HEI, long tube headers, 650 Edlebrock on an Air Gap running 14°, 268H CAM, no AC, and a new 700r4 with corvette internals and no lock up. I cruise at 60/1800 rpm on 30" tires and a 3:73 gear set.

Before I started the build, I had a clapped out 350 and TH350. I got 12+ MPG. With the new setup, I was hoping for 14-15 and get between 8-10 on a good day. Confusion reigns.

I was told that the Air Gap cools the mixture for more HP at higher RPMs at the cost of lower mileage due to less atomization in the colder mixture. I am at a point where I am considering a F.I. conversion kit and replacing the Edlebrock 650/Air Gap combo. . .

My neighbor gets 24 MPG cruising with his 10 year old F350 4x4. . . now that's a pisser! I am not sure what part, or parts, of my combo are wrong, but 8-10 MPG wipes the smiles off my face every time I fill up and looking at it sitting in the driveway while I drive the '98 Silverado. . . well, that's just as bad.

 

[Green79Scottsdale]

I cruise at 60/1800 rpm on 30" tires and a 3:73 gear set.

I remember seeing somewhere that you will achieve your best mpg when your engine is at its peak torque. True or not, I can't confirm.

I have also heard that to achieve the best mpg, you want you engine to turn the rpm where max vacuum happens. Hook up a vacuum gauge and go for a cruise. You may actually be lugging the engine at 1800 rpm. Check and see what your vacuum is at 1800 rpm, and then drop it into drive and see what you get for vacuum at 2200, 2500, maybe even 2800 rpm. If you get max vacuum at 2500 rpm, that is where you will get max rpm because your engine is hardly working to maintain that rpm, even though if it 700 rpms higher.

 

[Obwonkonobe]

Well, I see I am not the only person with this confusion.

I have a '74 with a .030 over 350 high nickel content block, full rebuild, HEI, long tube headers, 650 Edlebrock on an Air Gap running 14°, 268H CAM, no AC, and a new 700r4 with corvette internals and no lock up. I cruise at 60/1800 rpm on 30" tires and a 3:73 gear set.

Before I started the build, I had a clapped out 350 and TH350. I got 12+ MPG. With the new setup, I was hoping for 14-15 and get between 8-10 on a good day. Confusion reigns.

I was told that the Air Gap cools the mixture for more HP at higher RPMs at the cost of lower mileage due to less atomization in the colder mixture. I am at a point where I am considering a F.I. conversion kit and replacing the Edlebrock 650/Air Gap combo. . .

My neighbor gets 24 MPG cruising with his 10 year old F350 4x4. . . now that's a pisser! I am not sure what part, or parts, of my combo are wrong, but 8-10 MPG wipes the smiles off my face every time I fill up and looking at it sitting in the driveway while I drive the '98 Silverado. . . well, that's just as bad.

Honestly if you go fuel injection I’m starting to think I should’ve gone with a factory tbi setup, and built that out. Or the Holley sniper, you have WAY more control over those sniper units. But for simplicity you can’t beat the msd atomic

 

[SquareRoot]

Honestly if you go fuel injection I’m starting to think I should’ve gone with a factory tbi setup, and built that out. Or the Holley sniper, you have WAY more control over those sniper units. But for simplicity you can’t beat the msd atomic

Your better off stabbing your eyes out than thinking about the Holley Sniper. Biggest POS ever made. Do your research.