I purchased a low mileage (80,000) 1973 Ford F350 Super Camper Special with a stock 390/C6/4.10 running gear and thought it would be a TOW MONSTER. I picked up a 6,800 lb trailer yesterday and was very disappointed in the performance, I had to push it hard to maintain 50mph and it would slow down on even the smallest hills, I have an Edelbrock performer intake and 650 cfm Carb I will be installing plus I just had 3" exhaust put on, I guess my question is should I get an RV Cam to install as well and should I switch to 373 gearing or am I just wasting money?

Right now at 50 MPH I'm at 2600 rpm on my Tach and the speed limit here is 70 mph.

 

I would check 2 things right off that are inexpensive that will tell you a lot as to what direction you want to go .. Check compression of the motor and make sure trans is not slipping and has good clean fluid .. Post back progress

 

Nice looking truck.

I would say with intake and exhaust modifications, it should get better. There is no real sence if doing an intake and carb, if you are not going to update the exhaust as well.

Don't forget to address your timing as well. Many things could cause your truck to not live up to your expecations. A step by step, mythodical approach should get you going in the right direction. Remember not to change too many things at one time, or you'll be left chasing your tail.

I would leave the gear change for the last step once you get the engine running to your satisfaction.

 

Just had trans serviced at trans shop with new filter, gasket and ALL fluid replaced. The shop gave trans a 100% and they believe the miles to be original on the truck.
Brand new 3" exhaust system was installed at the same time!

I will have to do a compression check, the story on the truck is the womans husband passed away and she move the truck from the garage into a field beside her house so she could park in the garage and it just sat there for 10 years, I flushed the gas added a new battery and added a can of sea foam and a bottle of octane booster to each tank, I am now on 3rd tank of gas and it runs great, no smoke or oil consumption, just can't keep up when towing! feels like the gearing is wrong!

 

3:73's will make the truck less desirable for towing but allow you lower rpm's at higher speeds .. on the trans side you might consider a torque converter set up for towing after you squeeze what HP you can out of the motor .. The compression test should tell us a lot about the motor right off .. My hauler was a 4door F350 with a 460/C-6 with 4:10's and at 3000 rpms you were at 65 mph the solution for me was an over drive tranny but with the 390 motor you don't have many options .. You can go with a gearvendors overdrive unit $$$ and/or go with the tallest tire that will fit under your current suspension .. remember that truck was set up never intending to go 70 pulling a trailer

 

Is it dual 3" exhaust?

 

390s/360s almost always seem kind of limp with an auto trans behind them

 

Timing, compression, carb calibration, fuel delivery, all have affect .... and what are you comparing it to? You are pulling an empty 6800 pound trailer that also moves a lot of wind. The C-6 has no OD, no lock up, its got TC slip built in.

I'ld also install a vacume gage.

If that is an Edelbrock 650, check fuel pressure from the pump, they like 5.5 psi, with 6.0 psi as MAX.

And 3" dual pipes is a bit overkill on a stock or near stock 390.

 

I use a 75 4x4 390, 4 spd NP435, 4.10, and tow about the same size trailer. I'm going to look for a little taller tire, I like the look of a full wheel well anyways. I do have an overdrive unit but don't use it when towing. I tach about the same, 2700 @ 55 MPH. It labors on big hills but gets me from point A to B and is always a topic of coversation at the campgrounds. Good looking truck, don't give up on it!!

 

Just like RedRoad said, swapping to 3.73's will make it struggle more on hills. If you are wanting to do a gear swap, you want to go to a lower gear ratio, something like 4.56.

Have you done a tune up on the engine since you've gotten it? Just because it's low miles doesn't mean everything will still be in quality condition, especially since it's been sitting. I would change plugs, wires, cap, rotor, points and condenser, change the oil and filter, fuel filter if you have one, air filter, etc. At the very least, re-gap all the plugs and points/condenser

You could also look around for shift kits for your c6. There are ones out there specifically for towing. I would look around and suggest some, but I can't go to any other forums than this one because of the damn school content filter


Jameson

 

The main thing that jumps out is the exhaust. 3in is major over kill on basic stock 390......wait, are you still running the factory exhaust manifolds with a 3in exhaust or do you have headers as well?? If you have the stock manifolds with a 3in exhaust, that's your biggest issue if the other mentioned items pans out and are in good shape. (plugs,distributor, compression, filters and such.)

 

Headers for sure. The stock manifolds are very restrictive. Dual 2 1/2 or single 3" exhaust. The 4.10's are fine. You'll need the rpms. Install the biggest tranny cooler you can fit. The tq converter is does not lock so it's always churning the fluid, making heat especially if you drop to 2nd. Remember that 390 is only a cpl hundred horses if that and not much more tq. Not like the tow beasts they make today. On another note, ST trailer tires are only rated for 65mph. No need to go faster than that really.

 

When i tow with my dent i drive 55 no matter what the speed limit is. Even through school zones...just kidding.
To tall a tire and wheel combo will negate any improvements made by lower gearing. You can tow with a dent. You just need to think by 1970's standards. Unless you want to invest a whole lot of capital to make it like a newer truck. and by then you could have bought said truck.

 

You're wasting your money...

 

And I agree with whomever said add a big cooler .... and I'ld also say a shift kit that eliminates soft shifts. I installed a Transgo kit in my C-6 back in the late '80s when the truck was still under 40K miles old and it still works.

Big cooler is mounted between the radiator and fan on my truck, it's after the radiator cooler in the return line .... I think? It was a long time ago that I plumbed it.