One parting thought for you
FORD won more than anybody with the FE F250 platform in the 70s. Some key tricks were learned by spending a lot of FORD money and by race engineering to win, a lot. I would have been fired on the spot for sharing a few tricks below, but, 40-45 years later, I think we are safe HAHAHAHAA Besdes, we hired the Boss' son years back,,,so,,,we all love the old trucks and want to see everybody have fun. No sponsorships to lose here HA HA
An race truck is a special deal. And FE is perfectly suited to win off road, it is a torque monstor if done right, and with a tall gear, say racing the BAJA 1000, they were very hard to beat !!
Imagine a trick F250, with 3 shocls per wheel, and a fully triangulated race chassis, tall BF Goodrich or Firestone 15 by 10 desert race tires, full floating rear axles with knock offs on aluminum mags, and over 140 MPH down a sandy beach,,,floored for mile after mile YEEE HAAAAAAAAAAAAAAAAAA
So
Your 3500 altitude tune up could be a tad lean at seas level. Let us know this, will the truck always run at 3500 ft? Will it coome down to seas level too? Will it get some action at 4000,5000, 6000 feet to? Hey, we all gotta climb that mountain to say we did it, ya?
ha ha
Here is what we did racing up Pikes Peak, or over on the Barstow to Vegas races, or, the Mint 400 races.
For max power, floored, on a race ngine...and you have a nice motor there...the 2 general tuning rules can help you get in to a safe zone a bit easier. Just info for you to use on the basic tune up
I would reduce the main jets, around 1 number, for every 2000 feet above sea level, if, and only if, you goal is max power while floored for top MPH and lowest ET
So for you, maybe is she likes, lets guess, 72s and 76s,,,primary and secondary jets
If we are hangin it out over half a mile in the sky,,,,3500 ft,,,your barometer, temp, density altitude, water grains will factor in heavily, if we tune off of a weather station, sure, but given STP,,,standard temperature, and pressure (atmospheric) Id start with 2 steps leaner
70s and 74's
You will not kill a pump gas FE being a little lean, and it will act crisper,,,and less boggish,,I HATE FAT FUEL CURVES if un necessary !! LEAN IS MEAN
NEXT
At altitude, the base tune up usually wants a little more initial advance
I would curve your distributor by pulling away a little mechanical advance, and a bit of vacuum advance, Id raise the start stop points there, then add 1 to 2 more degrees static
So since you have fast burn BBM heads you say, do the R and D,,,,,and maybe, if we pick 34 degree total timing.... and your distrib has a curve set for 24 in the mechanical advance, so 10 is on the damper,, 10, plus 24, for 34 total, no vacuum...I would change my curve, to 22 and 12. Do a base line before and after
You can acceleration test up there real easy too with a stop watch
Find a nice 1/4 mile out in the boon dock,,,,some safe place where you can mark off a nice flat 1320 feet...and be safe.....and make 10 runs and time them. Be consistent
Then use your hand tool,,,,,jets, timing light, vacuum gage, and plugs, and the spark plug reader....and so on
And see, by testing, what that cool F250 wants. She will tell you, every run, if she is happy as you adjust her to a nice state of tune
Have fun
And of course,,,,if you come down the mountain, for a race at seas level,,,,,use your note book,,,,maybe add some jet size back,,,,say plus 2 plus 2 and then pull the leed ie base timing,,,back 1 or 2 degrees,,,and re test her
And if you get a match race, decide to pull off the mufflers,,,lose the air cleaner, then add jet and add some advance, and so on
Just basic tuning
We won Pikes Peak and set a record that stood for years with another little trick
a 13 to 1 race motor at seas level,,,,,,has much much less cylinder pressure at a mountain race.
If we need to haul arse from 5000 ft altitude, up to say 8000 -9000 feet,,,,,guess what? You can run much much more compression, just to get the engine to squeaze the charge, like it does at sea level. We ran, say, BOSS 429s,,,,and stroked 427 High Risers, a few SOHCs,,,,way way up to 14-1 15-1
Here is a general knowledge missive for you and maybe it can help
The Holley suggestion of decreasing jet size by one number per 2000' elevation is a good starting point. You might want to experiment with power valves too. To check and verify your experiments, find a long section of relatively straight highway, drive at your normal cruise speed for a few miles then put it in neutral coasting to a safe place to park off the highway. Pull all of the spark plugs and read them. Use a lighted magnifying plug reader to verify that there are no aluminum dingle berries hiding down deep in the plug at the base of the insulator. Best plug condition will be a consistent light tan color on the insulator.
You probably already know this, but you will also want to advance your timing by a few degrees up on the mountain.
So using 2 or 3 sets of plugs can help you tune it. Allow some time to let the plugs color, or get enough deposits to see well dont read them when still white,,,let them color all the way down. Watch the color of each thread cloely,,,thread one tells a story, then thread 2,3,4. You will see the temperature, change the color of the sharp edge of the spark plugs thread,,,,this color is also, like a little temperature gage, or evidence...but the color, is first and best.
And be aware of how even all 8 plugs compare....you can sometimes bandaid a tune up depending on the intake and cam. Many FEs have won races stagger jetted. Not sure if we are racing though
But a perfect tune, on many intakes that are not optimized as to equal length runners, and equal intake port, tract, dynamics, do sometimes like a funny set of jets to get bitchin pyrometer readings on the dyno
Some of our winning race truck engines, for FORD, for class 1 and 2,,,real fast FE trucks,,,,did get stagger jetted a bit If you race, let me know. Our race trucks did some times have best power, with main jets out back, not the same size
Now here is a huge trick we also won with
a fast truck,usually sees a nice power gain, with a nice 2 inch, or 3 inch tall, carb spacer.
We used the 4 hole offenhouser spacer most. The good 4 hole spacers, reduce carb temps, thus add fuel density and cooling, plus, they mimic a larger plenum, and allow more jet.
Many FE intakes dyno better with a nice carb spacer,,,,but you cant fit them under many door car hoods. You can do a bubble hood, but on a F250, we also ran a 4 inch spacer, and a double stacked air cleaner,,,,,a 14 by 3, on top of a 14 by 3 air cleaner, and then a K and N oil foam pre filter around the air filters
Have fun
If you add some old FORD race Truck tricks to her, it would make a lot of old FORD racers smile
