This question has probably been posted many times, but others will probably appreciate a revisit besides me.

I have a remanufactured <a href="http://www.motorhaven.com/">390 </a>CI, 2bb, auto trans, in a 1972 F250 Camper Special. After the new engine was installed, I checked engine settings and found that ignition timing was up around 10 BTDC. I reset to factory 6 BTDC. The engine runs fine, but I wonder if I can improve performance and gas mileage by increasing the timing. I run high performance gasoline and engine does not ping. I should add that distributor is original vacumn advance unit.

After reading several posts regarding ignition improvements, I installed a Pertronix II ignition module. It works just as advertised and did a lot to eliminate a chronic flat spot I have with cold engine and right turns (<a href="http://www.motorhaven.com/">float</a> setting probably). I also installed a Hayden flex fan. Gas mileage is up from 10 to 12+. Nothing to write home about, but improvement nonetheless. I also had my brakes checked because of a brake light that would not turn off. Many responded to my question about this light with advise on how to center the proportioning valve. I took the truck back to a mechanic who recently performed brake work and he found that my rear brake cylinders were leaking. The light is now out, but thanks to this forum, I learned that it was on for a good reason.

My last question is: Can anyone tell me how to determine what type auto transmission my truck has and what are the merits of the different auto transmissions that Ford hooked up to the 390s in 1972.

This is a great forum and well worth the cost of membership.

Raintree55

 

10-12 is common BTDC timing for FEs. Generally run higher until it starts pinging.

Your auto tranny should be a C6. A great, very durable tranny.

20% improvement, is something I'd write home about. Is this just a fan change or an electric fan kit?

 

Thanks for advise on timing. Fan change was just the blade unit. Haden unit just replaces the stock blades and functions the same except that the pitch of each blade is controlled by a flexible piece of stainless steel that flattens out as rpm increases. When the blades flatten, the parasitic drag is reduced and the load on the engine is eased. In theory, reduced load should help gas mileage. You probably know all this anyway. I think the Pertronix II module replacing the breaker points made most of the improvement. Cheers.

 

just wanted to add that I installed Pertronix unit on my '72 390 about 5 yrs ago, got tired of messing with points all the time. Mileage is about 13 on the road pulling boat. I would have spent more on point sets in 5 yrs than I paid for igniton unit. Cheaper than replacing entire distributor. '72 F-100 4WD .30 over 390, Comp. cam, Edelbrock, Holley, Hedman, Accel, Scott wires,Flowmasters, 9qt pan, etc.

 

Hey Baitmaster-

Do you know what gears you're running in the rear? I'm having a hard time breaking 10 MPG with 3.25 gears and 31" tires.

Thanks-

Joe

 

not sure of gears, never looked in there, and no tags on housing. I'm running 33" tires tho. Plenty of guts with 390, so no low end torque worries with high gears and big tires. Especially with that granny gear!