Newtype 72 c/10 power/drivetrain HELP

[NewType72]

Well I plan to have this truck a long time I can't afford the immediate price but I can swing them thru beats "bill me later" option. I want to be happy with this next motor setup because I fear that if I'm not happy yet again it'll discourage me on this truck. I'm not dead set on thorleys I know they're pricey. My father has loved them in the past when he was building trucks and I've never heard too much negativity toward them so they became a top choice. I'm just simply looking or input and I thank you and the others for all the help on what to look for and try out.
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[66Submarine]

About the fuel economy thing. My father's 66 C-10 gets around 18MPG. It has a 3.11 first gear Saginaw 4 speed manual, 3.07 gears, and a 31x10.50r15 drive tire. The engine is a flat top 350 with vortec heads, very mild sealed power CS274 RV cam, rams horn iron manifolds, and an Edelbrock 1406 (Carter copy) carb. (Runs real nice, but will spark knock if you lug it down on 87 octane. ) Generally he drives 45-55 around town and 60 or so on the highway.

So, IMO, (and IME) don't drive like there's something wrong with you, don't have a carburetor with a sunk float and the idle mixture screw falling out, and you'll get respectable mileage with these trucks.

You'll also hear about getting 10-12MPG with a 250 inline six. Again, with 3.73's, 31x10.50r15's, a 250, and a three speed, my '65 C-10 got 18+MPG, and it's so worn out it would burn a quart of 15w40 every 100 miles or so making that run @55MPH.

And, no, these numbers are in US gallons, and they are figured using google maps for the distance and filling the truck with a can and dipstick by fuel weight.

Anyway, that's been my experience, as they say, YMMV.

[NewType72]

Man what a wealth on getting all those numbers down I know it's far more than just slipping the right trans behind the motor there's so much that take into account honestly I know my fat 10" wheel/tire combo is killing me on any kind of mileage I probably still run 12 best and 14 on a great downhill but with my upcoming setup I'd be more than happy to have 15 and a great running truck. Gas prices don't really hurt me as long as I'm happy driving my truck. I don't rate it as MPG but more as smiles per gallon
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[66Submarine]

15 should be real doable with something that's tuned up well. I'd start with the carb, myself. Holley's are very tunable if that's what you have, and Quadrajet's are very good carbs for economy. The Edelbrock 1406 AFB I mentioned earlier is already set up for mileage out of the box, and has done well so far on the truck it's on, if you're looking for something you can more or less bolt on.

Whatever carb you run, one thing I'd suggest is to run the idle mixture as lean as you can comfortably deal with when it's cold. (Tuning with a vacuum gauge I normally go a little lean past max vacuum at operating temp.) I personally think the idle mixture plays a bigger roll in fuel economy than most would think.

One thing I also forgot mention before is fuel pressure. A crappy generic fuel pump can make too much pressure and push fuel past the needle and seat at times, causing poor mileage and potentially making it run like crap. I'd recommend always running a good fuel pressure regulator to make sure that doesn't happen. You could try that now and see if your mileage improves any, 5PSI or so should be a good number.

Also, another thing I'd think about is a manual trans swap. I don't know how you feel about that but thought I'd throw it out there. A lot of people run 700r4's and 4L60's, but I'd never personally put one in a truck I was going to keep for any length of time. A good Saginaw 4 speed, clutch, 3.07 gear, and Hurst linkage like the '66 I mentioned has will be less than the auto-tragic and will almost certainly outlast it several times over in normal driving. Burn up the clutch 100,000 later? Rockauto has the whole kit for less than $100, and it only takes an hour or so to change. A T-5 5 speed would give you your overdrive if you want to keep your 3.73 rear, and they are common and not that expensive. Might be something to look into.

I also think the four speed adds some extra "smiles per gallon", for me it does, anyway.

[cubber]

Dang...where's this guy been? Some good info and advice! I like it!