Trading some work for a 1970 F100 2wd and a(not in the truck) 300 six with a 435 4 speed. The truck had a 360. I have all the mounts, radiator, everything to install the six in the truck which I plan to do. I'm considering driving the truck if it will pull of better mileage than my 70 f250 4x4 with a 390 that squeaks out 15 mpg on the freeway. 90% of my driving is freeway and around 20% is with trailers over 20K pounds. I wouldn't consider towing with the six powered truck. Just using it for long empty freeway drives at around 65 mph. The engine is a bone stock unit from a 73 F250 that appears in good shape. I am curious what might be smart and economical upgrades to make to the engine for best gas mileage and also, what cruising rpm will this engine be the happiest at so I can dial in the appropriate rear end ratio for highway use? The engine will get a thorough tune up and rebuilt carb. Thinking along the lines of exhaust recomendations, ignition, overall efficiency, not max power. Thanks.
Dustin

 

This is what I plan to do to my pure stock 71 F-100.

Complete Petronix Ignition
2BBL Carb - If I can steal a 4BBL manifold off EBay, I'll use an adaptor to mount the 2BBL on the 4BBL manifold. If I find a brand new 4BBL smaller card(390 - 450) I would use that as well.
EFI exhaust manifolds.
2n1 Walker downpipe into a quiet full length exhaust system.


BTW:It appears for best mileage you want your six turning about 2500 rpms at cruising speed.

This what I have planned, it fits my truck and my budget. If I had a bigger wallet, who knows

 

if your really up for it, you can try to find a mazda 5spd from the newer FI 300-6s, that will give you an overdrive which will increase gas mileage. if you don't want to put a mazda 5spd on, you can get a gear vendors under/overdrive unit installed on the 435 and get split gears and an overdrive. as for the rest in my opinion, 500cfm 4barrel edelbrock carb should keep you running with good gas mileage. a higher compression ratio should be made, since its a 70s motor, which has about 8-8.5 compression, up it to 9-9.5 and that will give you a little more power, plus better gas mileage. EFI exhaust manifolds are a must. they are split exhaust manifolds (2- 3 into 1)and they are better flowing than the old single one, which will improve mileage. Pertronix will give you easier starts and better power and mileage. fan clutch will help mileage, as well as a low temp thermostat (160). if you go for the 4bbl manifold, get a 2inch swirl torque carb spacer, power and mileage are improved and noticed (i noticed a difference with my 390). as for gearing, if you are doing a lot of highway driving over city driving a really high gear would be my recommendation, i would say 3.00:1 or lower, depending on what you are doing with your transmission.

 

Thanks for the advice. I will look for the efi exhaust manifolds. I will keep the 1 bbl for now. If I do decide to keep the truck it will likely get port injection and edis ignition some day. Those M50D's are a real piece of crap tranny, but I would throw one in If I found one for cheap and could adapt it to mechanical clutch linkage. I disagree with the 160 thermostat recomendation. Engines run most efficiently around 200 degrees. Rings and cylinder walls last 10 times longer if run at 200 degrees as opposed to 180. 195 stat keeps the engine happy and the heater working great. Thanks again.
Dustin

 

I understand 3:08 gear ratio rearend is a high way gear. and since thats all your gonna use this truck for is mostly high way, and not towing, 3:08s should be good. you might be able to cruise at lower RPM's with 2:73's im not sure, but those gears aren't really great.

 

You won't want to go with any higher gear than your 3.08's. The 435 tranny combined with the 3.08's is an ok compromise. That's the setup I had in my 84. It did ok on the highway. Even with the stock intake and exhaust manifolds (i replaced the goofy carter feedback carb with a regular 1 bbl), i was able to pretty consistently get 15-18 mpg. It didn't make much difference if I had a topper on it or not, nor did it seem to matter if I was driving in the cool, dense sea-level air of Western WA, or the drier high plains air of Montana and South Dakota, the mileage stayed the same. I did notice the gearing if i had any load on the truck.

 

I think that my 77 with a 300 comes with 2.73 gears in it from the factory. it spools about 2500 going 65 on the highway, which the motor thoroughly enjoys. keep it aroud 2200 to 2500 and you'll be fine. The 2.73 isn't the greatest for towing and such, but just for driving around, it'll work jsut fine. I got a three speed in mine, anybody know if that gear vendors overdrive aill mate up to it. I'd like the overdrive and some extra gears between second and third.

 

gear vendors has a unit that will fit any rwd setup. they have a divorced unit that can be installed behind any transmission

 

Well, this project was going to be quick and painless, but I found an injected 300 six powered 89 E150 van with 60K miles and running perfect for $500. I figured it would have the AOD, but it actually has a C6 auto. I'm going to put the six in without any of the emissions components with a megasquirt controller and the 4 speed for now. Turns out it's a T18, not a 435 like I thought at first. I'll find a 2.73 or 3.00 centerchunk for the 9", whatever's free or really cheap. I'll get it up and going then stay on the prowl for an M5OD or a dodge nv4500. Really like the serpentine belt setup and the saginaw power steering pump that's on the engine too. Does the 89 six have a roller cam or anything else making it different from the carbed sixes? Thanks.
Dustin

 

thanks 47. I thought that it was generic to all rear wheels, but the bellhousing and clutch setup for the three speed are a little different than usual. Hate to drop the bucks and have something that dosen't work.

 

what is the part number for the walker down pipe?

 

Ammis tell me about it I have a 3 speed with stock overdrive and would like more I ask them and they said it would be no porblem the major mod would be the driveline

 

yeah, sounds like I would need a custom driveshaft though. Anybody know what one of those runs in the $ ballpark. Average might need to know if he's gonna put that dodge tranny behind the ford,(assuming he dosen't know already) and I would like to know to put the overdrive on mine.

 

I think it all depends on what the driveline shop in your area wants to charge the other option is letting them install the overdrive.

 

Complete drivelines run around $200. You can have your old unit shortened or lengthened for alot less. I've done 2 other NV4500 conversions, both 4x4. A 2wd conversion would be cake. I had new drivelines made for my nice 70 f250, but my other trucks I just shorten them myself. A very easy way to get around having to balance a driveline after you whack it is to cut the tube to length and press the end back into the tube leaving 1/8" for weld. Put one small tack on the end and put the driveline in place in the truck. Use a dial indicator on the driveline tube next to the yoke you cut and with a hammer adjust it to within a couple thou TIR. I use 3/32" 7018 rod to weld it up and I do it while it's in place. Never broke one and they don't vibrate. Good luck. Sure would be helpful to get some info on my fuel injected six. This forum must not get alot of traffic.
Dustin