- Economical Cruising Speed is too low.
- With a 2.75 final drive in the 9" rear end and a T-18 4-speed transmission, 1500rpm is 50mph. The engine is comfortable at this speed and gets its best fuel economy, a fairly steady 19mpg dipping occasionally (depending on wind, hills, ethanol fuel content, etc) to 15mpg and rising occasionally to 24mpg.
- I'm patient and don't mind 50mph, but the rest of the traffic is beginning to pose a threat to my safety at this speed, so I want to go faster.
- Gearing for towing heavy loads up hills is insufficient
- I can tow really surprisingly heavy loads with this truck, but because of the very wide gap between gears in the T-18, I'm often far slower than necessary up hills.
- The engine seems to produce its best comfortable power at 1800rpm, which in 4th (top) gear is 60mph, but in 3rd gear it is only 35mph. The result is that when I encounter a grade that is too steep or too long for me to hold 60mph on it, I have to slow to 35mph in order to get the engine in its good working range. At that speed, usually, it's just smoking cigarettes, it's not even challenged. But 4th is too far away to be useful.
- More Power, Please.
- The engine is an unmodified 300 six from 1979, with a Motorcraft single-barrel carb and transistorized ignition. If that carb isn't original, it's been on there since God invented dirt, because a surprisingly prodigeous quantity of ancient dirt is caked up all over it.
- Everybody would like more power, but I don't think I'd like to have it if I have to sacrifice economy. The 20mpg mark is pretty near my lowest tolerable level, I think. Once I have a gear that will let me pull grades at 45 or 50mph, I'll be happy even if I can't muster up any more power to stay in top gear longer.
The New to Me Truck:
- 1969 3/4-ton camper special, also with a T-18 but originally with a 360 motor, which I pulled out and sold for scrap.
- From a junk yard, a 300 six cylinder with a 1977 emissions sticker on the valve cover but no smog in the head. Just heard back from the machine shop, the no.1 cylinder (worst one) is 0.032 thousandths out so the block will have to be bored 0.040 over.
- Engine Quest cast iron head with improved water jacketing and heart-shaped combustion chambers (EQ Part Number CH300A). This head has smog and they normally offer a non-smog head, but didn't have one available in the timeframe I needed it so I just got the smog head. This head ought to raise compression slightly and give a cleaner, more efficient burn to improve economy and power.
- Cast iron exhaust manifold from an old 60s dump truck. Now that I have it in my hands, it really does look significantly bigger than the original. And I like the idea of using the original heat transfer design.
- I'm still looking for an intake, I guess I'm going to use a factory log one if I can find it cheap because none of the aftermarket ones readily available please me.
- Autolite 2100 2-barrel carburetor on the way, from Gotta Fish Carburetors, 1.14 venturi (300cfm) and #50 jets. I'm kinda hoping those will just work great but if not I'll get the jet kit and play around with it.
- Isky Mile-a-mor cam on the way (Isky part number 331-MK) along with Isky's recommended Lifters, Pushrods, Valve Springs, Spring Shims and Retainers. I'll use the original rockers, unless somebody convinces me otherwise.
- Spicer 3-speed auxiliary transmission (the seller referred to it as a "Watson" or "Brown-Lipe" box, said it came from a 50s or 60s Ford Dump Truck). This box's gears are: first-2.03 underdrive, second-1:1, thrid-0.75 overdrive. This box should give me the splitting capability I need for those long grades.
Well for the benefit of us all, I intend to post my progress on the truck here so we can all learn how this combination of stuff worked out.
In the mean time, please feel free to post your opinions on my choices so far.
I'm still on the fence about the rear end and the intake. The Offy C series intake got serious consideration, but its own advertisement promotes its commendable qualities in the 2500-7000rpm range which, frankly, makes me sick to think about ever turning 3k much less 7. Good Lord. Doesn't anybody make a nice, heavy, conservative cast iron intake that's just a little less aesthmatic than the original and with softer runner profiles?
The rear end is in question because the new truck has a Dana 60, which is unquestionably a great rear end, but it looks like the tallest gearset I can get for it is 3.54. Well, according to my precise and accurate calculations, a 3.54 together with my fancy new overdrive will put me at about 52mph at 1500rpm, which is where I already am with my 2.75 9-inch. I really do want to go faster, and I don't mind going up to 1800rpm if necessary to do it, but I kinda think that head and cam and so forth ought to improve my torque enough that I should be able to cruise at 65 or so at 1500rpm, if only I had tall enough gears. Any and all of your thoughts on this brain-buster are welcome here.