Hi,
I have a Ford 1973 Ranchero GT (351c (rebuilt), 4-bbl) which I have had for about two years now. During this time I've had three full tune-ups performed from two different establishments. The most recent tune-up was performed just before I left to go on a trip to the mountains not that long ago.
The motor pings bad at sea level during high acceleration or going up the local hills. Yet runs surprisingly strong at an altitude of 6-7000 feet.
The power curve seems to dip the lowest at around 2-3000 feet. It was just chuuuuugging on the freeway at about 40MPH as I kept my foot off the gas (something I don't have to do on the freeway at sea level) to prevent the motor from pinging going up a slight grade...
/ \/
Forming a check-mark shaped power curve in the process.
None of the previous full tune-ups have stopped the pinging at sea level and this was the first trip with the truck at these higher altitudes. So I was surprised at the performance and lack of pinging. It must in part have something to do with the thin oxygen at higher altitudes.
I have the original 1973 Ranchero owners manual and the manual says that
93 octane fuel should be used. The best found around here these days is 92 octane. I can't imagine that one octane level is the problem. Especially since I used 92 octane throughout the entire trip.I was told by one tune-up place that pinging was a problem with Ford motors of this size during the early 1970s and I don't want to live at
6-7000 feet just to have a vehicle that doesn't ping. HeheSomeone else suggested I looked on AllData. The closest match from the Automotive Recalls and Technical Service Bulletins were for a 1973 Ford Truck Ranchero V8-351 VIN Q 4-bbl. The TSBs are:
TSB Number Issue Date TSB Title ATRATB024 SEP 90 A/T - Harsh Reverse Engagements ATRATB8761 NOV 87 A/T - C6 No. 9 Thrust Washer Failure ATRATB8658 NOV 86 A/T - Slipping Or No Third Gear After Overhaul ATRASIL8519 JAN 85 A/T - Modulator Chart ATRATB8543 JAN 85 A/T - Recurrent Sticking Valves/In Line Filters 8211A1 JUN 82 High Altitude Adjustments
I'm wondering if the last one, the "High Altitude Adjustments", has anything to do with the pinging? Maybe in a reverse sort of way?
There are no links at the site and I have repeatedly looked for the "High Altitude Adjustments" without much luck. It is just a wild guess that it has anything at all to do with the pinging.
Interestingly, when checking out other Ford vehicle of the same year at AllData, they all seem to have "High Altitude Adjustments" listed in TSB.
What are "High Altitude Adjustments"? How does it get adjusted? Is this even the problem?
Is this the fuel mixture on the carburetor? To my knowledge, the fuel mixture would either lean or rich the fuel coming out of the carburetor at idle and not limit the amount of air. Perhaps I could just let the air cleaner get dirty? Well, it's what happens when you are at your wits end. :)
Could someone /please/ offer some advice?