I'm back... Not much interest in the Bronco area, so I figured I'd post in here seeing as bullnose drivetrains are all the same pieces. I have an '81 Bronco that was originally a 302/C6/3.00 9" (engine is gone). I have an '86 Bronco with an EFI 302/AOD/3.55 8.8. I'm making one truck out of two, and had originally planned to swap the engine/trans/front axle from the '86, swap the gears in the 9" to 3.55, and end up with an EFI 302/AOD/3.55 9" in the '81.

I had originally thought that the EFI 302 was in good shape. Purred before I shut it off a few months ago. Go to start it and it lights right off with a slight rod knock which continues. Okay, that's my luck.

My goal for this truck is to make it the best daily driver combo, with plenty of torque to tow smaller loads, but still get reasonable fuel economy cruising.

I'm thinking of dropping in an EFI 351, mating that to the AOD and running the 3.55 gears, which would put me at about 1800 RPMs cruising on the interstate. If I were to leave the C6 and the current gears (3.00), it would be running at about 2200 in final gear, which seems a bit high.

What do you guys think? Interested to hear from experience.

I have plenty of pictures if you guys are interested in the progress.

 

I do have experience with the C6 and 3.50 gears, and I think you are off several hundred RPM unless you are running big tires. Rusty ran about 2600 RPM at 65 MPH with that combination and 31" tires. And the C6 is a thirsty tranny.

So I'd vote for an AOD with its OD and lock-up torque converter. But, I don't think it will live long behind a 351 unless you have it beefed up. Ford didn't put it behind the 351, and that surely the reason. However, aftermarket parts are supposedly available to make them much stronger.

And, I'd not rebuild a 302 when you want torque. The 351 will cost about the same to rebuild and the longer stroke gives more torque for the same build otherwise. Yes, you'll lose some economy with the bigger engine, but the AOD will help get that back as the 351 will allow it to run in OD a higher percentage of time.

 

That was my thinking as well. I figure at some point I'll grab a spare AOD and rebuild it to withstand the 351, but I don't plan on building an engine for power, rather good torque that a truck should have to work, and fuel efficiency. Also, conversion to mass air will be in it's future after everything is set up and I know it all works properly.

Also, Gary, thank you for putting together the GarageMahal. That's an awesome compilation of data that must have taken forever.

 

That's a labor of love, and it has taken me about 1 1/2 years. Actually, that's about how long it has been up, but I just keep adding from time to time to answer questions, once and for all.

 

I would not use the EFI unless you like playing with wires and are prepared to fix it yourself when it has problems. I would convert to a carb, and then you can reuse your fuel system on the older carbed chassis.

 

I know enough about the fuel injection to fix it. Eventually will be converted to mass air though, which I've never really had issues with.

There are benefits to both carb and EFI, and usually I like carburetor setups for power... but this is a daily driver I want to be as reliable as possible and as good on fuel as I can get.

 

I actually prefer EFI, but you do need to know how to work on it. Some people with EFI absolutely refuse to try to learn to pull the codes when they have a problem. But they still want to fix it themselves?

 

I have two scanners that can read and work with the OBD-I/EEC-IV. Got pretty good at reading flash codes, but the scanner saves a hassle. I've trouble shot some wacky things and I am familiar with the sensors and operation for the most part. Not afraid of books ether, so really the EFI doesn't scare me.

 

The other crazy idea I had was dropping in an EFI 300 I-6 in front of the AOD and keeping the 3.00 highway gears. I know from experience the 300 likes the low RPMs, and has great torque. I had that setup in my '80 F100 with 2.47 gears out back, it was hopped up a little and that combo worked really well cruising all over and pulled hard. According to Randy's Ring and Pinion (not sure how accurate that quick calculator is), Over drive is like 1500 rpms with 31's, and dropping down into drive is around 2200... which would work for towing stuff around.

 

I would ditch the EFI, just swap a carb and intake and call it a day. Also ditch teh AOD, they're car transmissions and not suitable for a truck. Youmentioned daily driver and reliability, so if it were me definitely no EFI or AOD in that case. I would do a 351w and ZF5. Not sure on build, but these days for a daily driver i'd probably shoot for 87 octane, I saw a 50 cent spread from 87 to 93 the other day. It might be worth the MPG hit to drop compression and run **** gas.

 

Definitely not putting a manual in it. I like the idea of the AOD for the non-computerized overdrive, and they can be beefed up to take the light abuse I'd throw it's way. The C6 just doesn't appeal to me all that much... too much power loss (inefficient) and no overdrive, albeit reliable as all heck.

As for the EFI, I've had both and built both. EFI is certainly more challenging to modify for performance, but that's not really my game plan. Both systems seem to work well when dialed in and running right. I just figure for daily use, the pros of EFI would be slightly easier cold start, better off road on angles, and better mileage (at least after converting to Mass Air).

I think I'm torn between the 351w and the 300. 351w would have plenty of power for anything this truck would ever do, but the 300 is in my book the king of simplicity and reliability (not to mention how much more room in the engine bay it leaves.). My 300 4bbl with a 268 comp cam and header rocked and rolled in my old Flareside and was a joy to drive.

 

You know... just go Bosch CIS mechanical fuel injection

No, just kidding; as fantastic as it is when it works, it's taken me years to truly learn and understand how it works (Bosch has a neat book on it that I've only JUST discovered), and replacement parts can be pricey. I've got CIS and CIS-E on my older Benzes, and I've finally gotten the system to be happy again on both. Will be going for EFI when I have the time.

I think for what your ultimate goal is, you've got the right idea in mind, and the knowledge to keep it maintained.

There's a thread over in the '87-96 section that talks about adapting a more modern 6-speed auto: https://www.ford-trucks.com/forums/1...peed-auto.html

See post #9. Might be an option if you choose the 351; if you plan to keep it for a long, long time, may as well look at all options and build it right. However, I know you mentioned you liked have a non-computerized overdrive.