I have a full size Blazer K5 with 350CID/TH350, 4.88 and 38" tires. When I am at 60mph my motor revs ~2500rpm, and I get a horrible MPG (around 10mpg).

I have a complete TPI from an 86 TA (305) and whas wondering if my mileage would be better with TPI than my Edelbrock 750.

The main conserne is how low gearing I have, and perhaps I am not gaining so much by changing to TPI.

The cost of the swap should be minimum, because I have everthing to do it except bigger injectors and chip.

So....do you think I will get more MPG with the TPI, and if so, how much better (15 MPG??)?

Nonni
86 TA, 305HO
81 Blazer K5

Three things right off are hurting your mileage.
First it is a blaizer, not aerodynamic at all, it has to "blast" a hole in the air as it travels.
Second the TH350 is only a 3 speed, no overdrive.
Third your rearend gears, looks like it is geared to run the 1/8 mile.

Also, depending on how "built" your engine is that 750 carb might be too much.
I don't expect you'll see much of a gain with the TPI if everything else remains the same, assuming it is presently in a good state of tune.

The gearing with 38" tires actually isn't sooooooooo bad, but the other points remain valid. The TPI might gain you a few, like maybe 2-3 MPG, but your main function should be to put an overdrive tranny in there or perhaps add an electronic overdrive from an older towing package to drop those revs.

A guy here at work had an '80's half ton Chevy 4X4 running close to 18 MPG highway on a 350 TPI with an overdrive AT in it. He said he had 33" tires and somewhere around 4:10 gears in it...

Yeah, I know, my Blazer has is to move a lot of air, and it has no overdrive (to exspensive to change that).

The truck was built to use mostly off road, thats the reason I have so low gears, and it has a pretty big tires (38").

I was just wondering if there would be better to use that TPI I have, cause it will cost me very little to swap. TPI is also better than carb in very step hills. But if I will not see any gain in MPG then I will not do it.

My engine is in pretty good tune so perhaps its the best to stick with the carb

Thanks,

Nonni

Sell the TPI, then unload the TH350 trans once the 4 speed OD is in. You should come out ahead if you play the game right... not to mention the better mileage paying for itself eventually.

I am sure it would be the best way in USA, but there is no market for TPI in Iceland. Used TH700 for 4x4 vehicles cost around $1000, if I could find one, and if I want to buy it from USA then I have to pay $$$$ in freight and custom duties.

Then I will have to move the transfercase and buy two new driveshafts. That swap will cost me at least $1500. I have consideret changing to TH700 but it will take a long time to pay for it self.

Changing to TPI should not cost me more than $300-$500, because I have everything (dont even have to plumb new fuel lines).

Nonni