tbi 350 mileage
 

I'm about to swap in a TBI 350 into my 69 pickup.

What kind of mileage do you get? What is your setup (gears/trans/tires/etc)

Mine is going to be 2.73/sm465/2wd/ 255/45/20 /electric fan/synthetic lube in trans and rearend/lowered with airdam

I'm hoping to get 20mpg, but that may be a stretch. My company is reimbursing for driving my own truck, so the more mpgs the more $$$ I can spend on the truck not gas.

Re: tbi 350 mileage
 

My '87 would knock down 18 or so, as I recall. 350, 700R4, 3.42 rear. That is after I put in a reman engine; I bought it with a bad knock.

I have swapped a TBI 350 into my '74, but I don't have a definitive mileage number yet. I am still chasing a miss I can't seem to find.

Re: tbi 350 mileage
 

The donor parts truck I bought has the same setup and the window sticker says 19

Re: tbi 350 mileage
 

Well let me start by saying the tbi 350 is a love hate motor. Before i put the duramax in my 95 gmc it had the tbi 350. I had no problems what so ever out of it, it always started and ran like a champ. Only reason i didnt like it was because it you Couldent buy aftermarket parts for it. Now the fule mile's i got 6. The reason for that is the motor was a zz4 crate motor. It also had a 4l80e with 6in lift and 37in tires on it with 4:10 gears. So the miles very. If you run supper in the motor you can get 20 and im not joking but thats in a 2wd. In a 4wd u can look at about 15 to 17. So my advice is find a a vortec 350 they have more power and torque. Just my personal openion
Posted via Mobile Device

Re: tbi 350 mileage
 

:Yes but that donor truck is a tad bit more aerodynamic than our 69's. I had an 88 GMC shortbed reg cab 2wd with the 305/700R with 2.73 gear, 235/75/15 tires. It was an absolute dog. Best ever mileage was 16. Slightest little rise in the highway or headwind and it downshifted, even at 70. That 350 ought to do better. With an OD trans the 3.42 gear is thought to be just about right for all around use. Non OD trans the 3.08 is about right. You are on the right track.

Re: tbi 350 mileage
 

My '91 is a 350/5-speed with 3.55s and I've seen 22mpg with it.

Re: tbi 350 mileage
 

That's what I'm talking about!

Re: tbi 350 mileage
 

The '89 in my signature gets 12-13 city/14-15 highway. It sucks. I just put Bosch plugs in there with the four ground straps on them and I swear my mileage dropped. I actually think it likes the cheap plugs better. I dropped in a new O2 sensor and cleaned the injectors with some B&G 44k, but that didn't make any difference. Might change plugs again, throw on a K&N filter, and throttle body spacer and see what I get. Maybe a chip too.

Re: tbi 350 mileage
 

these engines are great, from the factory they don't run the fuel psi that they should. I would suggest an adjustable FP regualtor and then open up the airflow to the TB. A good source of info is http://www.cfm-tech.com/index.htm just my 2 cents. :metal:

Re: tbi 350 mileage
 

I also have 3.73 gears...... Syn. lubed rear-end, When I got a very good 700R4 transmission build, the up-hill driving was more efficient.... I ended up with a 22 mpg highway, cruising.

>> Practice.... backing off on your gas peddle when on a up-hill rise..... listen to the transmission..... You can back off and still keep the same speed..... saving gas.

Re: tbi 350 mileage
 

The TBI we use, always had a mystery "miss"..... Uh, a "bump" in the idle at a stop. The earlier 'Vettes had it.

Also don't assume the sparkplug wires are perfect.... I had the best MSD wires and the ends were not pressed firm enough, changing the continuity .... sometimes, making it hard to find.

Re: tbi 350 mileage
 

'94 K2500 reg. cab long box. I've got 265/75/16 tires with 4.10 gears and almost always get 13.5, and this is seeing a lot of stop and go farm driving. I don't think 20 would be out of the question, depending on how you drive. :)

Re: tbi 350 mileage
 

That is Good News too me! I have 1998 Vortec 5.7ltr 3.73's wit 285/65-16. I have no Idea what I get for mileage. The new motor has 89 miles on it. The gas gauge just dropped to 3/4 from a full tank. We will see. I would like to drive it conservatively and try to get 15ish. 3/4 ton and Tires do not help...

Re: tbi 350 mileage
 

This is a dead miss. It has new Delco wires, plugs (twice) MSD cap and rotor, and I've swapped in a good known distributor also. Timing set at 1 (with SPOUT disconnected). I got teh engine as pretty much a box of parts, and swapped out stuff with the original 350 that was in the truck. Changing plugs again, I see that the aftermarket exhaust manifolds for my '74 truck are really close to the #2 plug. I bought a used one off of CL, along with another plug wire. I am going to try that, then replace the wireset if it helps. I hope so, anyhow.

Re: tbi 350 mileage
 

Yep. The actual engine is bone stock. I have a drop-in K&N, true dual exhaust with hi-flo cats and Borla mufflers and a "Hyperchip" (that's what it says on it) that was already on the truck when I bought it. When I got that mileage it was only a few thousand miles ago, so probably around 195,000 or so on the clock. That was also with the current wheel/tire combo, which has rather short 285/30-20s on the rear.