I'm hoping to get some advice here...

I've got a 1979 F150 4X4 with a 300 I6, NP435, NP205, 9inch, and Dana 44.
My diff gears are 3.50:1

I've been toying with the idea of swapping in a diesel, but it is seeming more and more out of reach financially. So I'm considering my options, and thinking about rebuilding the I6...

I never, ever want to run above 3200 RPM, prefferably less than 2900. I will be 4xing it quite a bit, but it will be my daily driver. Later this summer I'm swapping in 35's, probably super swamper tsl's. My daily commute is only 7 miles.

I do not plan to change my gear ratio initally. I figure if I need to, I can use my granny gear to start in, it should be plenty low enough, and this tranny doesn't seem to have any of the typical troubles I've seen shifting from granny to 2nd.

I have a pretty light right foot, and while I do like a good run through the mud, I don't tend to just stomp it to the floor when I'm in mud... I use techniqe, or my winch, but rarely a footfull of gas. I also like to go up hills, etc, but have never been rockcrawling, and don't really plan on it, unless it's just a short patch on a trail I'm otherwise going down.

I don't care how little acceleration I have, I'm a truck driver and therefore used to accelerating slowly. I would like my truck to be able to hold interstate highway speeds however... (70-80mph)

First and foremost is low end torque. I want lots.

What do you reccomend? I've seen the Clifford Performance website... Most of the stuff there seems marketed to those who would wrap their engines out. I will not. Are there any other sites for the I6?

Should I just get a stock rebuild? My six has a gazillion and a half miles on it, and it's getting pretty worn out, although it doesn't really burn oil yet, it is getting up there...

Are there any good rv cams for my application? I don't really want to lose fuel economy, because with my stock 1bbl carb I'm getting 9 and a half MPG...

Any other suggestions?

 

Reading your post makes me think you want a nice running nearly stock spec motor. You can do your rebuild and raise your compression a tad with a head mill job or possibly a little higher compression piston. Stock compression is pretty low, so maybe you can inch it up towards 9:1. EFI 3 into 1 exhaust manifolds seem cheap and easy and would probably work better than headers for your low RPM usage. Clean up the intake and rebuid the carb to spec and you should be good to go without spending much money. The EFI manifolds and CR increase will give you a few extra ponies with reaching for your wallet like a 4bbl and a 7000RPM rework would.

Good luck.

 

how about small block chevy valves and a summit truck cam.

 

Do a search for "My Built I-6", the poster is Col Flashman.

Really nice buildup.

 

I would forget about rebuilding the 1bbl. carb. They are a gas wasting pig and do nothing for producing power. Read the sticky at the top of the page. All kinds of info for building the six.

Rebuilding basically stock is a good way to go. However, these engines are anemic. As far as a rebuild, I would center it around getting the engine to breathe better. This would improve gas mileage and power because the engine would be more efficient. I think for $1500 -$2500 you would have a great 300L6. If your going to spend money, might as well do it once.

 

I'd be all for bumping the compression up also because, it is awful low from factory plus you may need milling anyways.

As for performance for off road i'd want it to get out of it's own way. i like you am also a strategic sort of driver but, have been caught in some sticky spots a stock 300-6 has trouble getting out of.

For performance i'd get a offy intake (200$). I'd also get a aftermarket carb because, as said before the stock carb's are junk. I'd reccomend a holley 470 truck avenger myself for it but, that's just because you say you off road and they can be good for 45% inclines and is a much better all around carb. If your looking for a more street sorta carb get a 4brrl 390 cfm holley or 2 brrl 350 holley. I would also pick up some efi manifolds. As for a cam go to crane cams or comp cams or isky cams or such and talk to them for what kind of cam you should run. No matter what you won't be hurting your gas i'd guess at least 12 mpg with these mods and big tires.

If your in search of a rebuild kit check out northernautoparts.com they sell a full rebuild kit and you can upgrade to felpro gasket (i'd reccomend felpro) and other upgrades for about 300$.

 

Also vote for bumping the compression. Also vote for headers, the Offenhauser manifold, and a 390 4 barrel, which is plenty of carb if you retain the stock cam. Definitely ditch the one barrel and the really restrictive log exhaust. If you want low speed torque, you'll have to settle for less potential horsepower, but the better breathing modifications bump horsepower noticeably even in the 6's low rev range. It will accelerate even at low revs, due to the low speed torque curve.

I walked the walk when I built my own 300 six, just like I mentioned. The compression increase was obtained by milling the head, combined with .060" overbore to 309 cubic inches. That amount of overbore is pushing it a bit, but it's held up well for 117,000 miles so far. In retrospect, I wouldn't change a thing. I wouldn't trade it for a higher revving engine. It has way more low speed torque than the EFI 300 six in my 93 Ford, even though the EFI truck is geared much lower (numerically higher). I can lug it off the line at 500 rpm and easily pull the truck with a load at that speed. I also picked up a couple hundred rpm on the top end, even with the stock cam, due to better breathing. In other words, it outperforms my EFI six all the way across the rev range. Make sure you get straight up cam timing if you want low speed torque. Stock cam or similar grind, or an RV type cam.

More compression=more torque.
Headers, better breathing = more torque.

 

bump compression to around 9.0:1. rebuild the bottem to stock with ARP hardware. overbore if neccessary but dont exceed .030 unless u need to. rebuild the head with a 3 angle valve job and if u want a VERY VERY mild porting. a cam in the neighbor hood of 260-270 duration with about .450-.480 lift is a good choice. top it off with a 390 cfm 4 bbl, offy 4 bbl intake and some long tube headers.

 

As far as a lift for those 35's, a 4" will do nicely. You can go up to a 6" with out the truck looking goofy. I would keep it as low as possible to maintain a more respectable center of gravity.

Have you thought about using an electric fan? They can be good for a FEW ponies/mpg's. Check into a hotter ignition also.

 

When I rebuild I'll go electric fan...

I'm probably not going to lift it at all... I MIGHT go 2.5"... I figure I can make some clearance in the fenders...

 

First, 9mpg sucks. I get better than that with my untuned holley 390. I would suggest a torque cam, headers (or efi exhaust) and either a motorcraft 2bbl or a holley 4bbl. I drive about like you, and am pretty happy with my setup. I suggest the 2 bbl because they are cheap and reliable. Look on ebay for stuff as it is on there all the time. For gears, don't go lower than 4.10. I have those with 33s and it is a little too low geared for my taste. With 35s or 36s it should be perfect. Rancho makes a cheap 3" that will fit 35s fine. Ohh, I just reread it, and you want to go 70-80. Maybe stick with the 3.50s as mine is spinning over 3000 at 70. Like you said, first can compensate. Good luck, and have fun.