Towing at Altitude
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Joined: Mar 2005
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From: Santa Clarita, CA
Towing at Altitude
Hey guys,
I wasn't sure if I should post this is my home forum (73-79) or here, so I'll try here first. I've got a 75 F250 with 350 rear suspension. It has a 460 in it without smog (I'm excempt from now on...hooray!!!) My question is regarding altitude towing. I just got the truck and have yet to tow it any long distances. In about 5 weeks we are leaving to go to the Sierra Nevadas, our trip begins at 3000 feet and ends at about 8-9000 feet. I was told that my trucks performance will decrease as I climb higher. Since I don't have all the fancy fuel delivery altering computer stuff in my truck , is there any other way to combat this besides carrying extra jets. Any information is greatly appreciated.
Jeff
I wasn't sure if I should post this is my home forum (73-79) or here, so I'll try here first. I've got a 75 F250 with 350 rear suspension. It has a 460 in it without smog (I'm excempt from now on...hooray!!!) My question is regarding altitude towing. I just got the truck and have yet to tow it any long distances. In about 5 weeks we are leaving to go to the Sierra Nevadas, our trip begins at 3000 feet and ends at about 8-9000 feet. I was told that my trucks performance will decrease as I climb higher. Since I don't have all the fancy fuel delivery altering computer stuff in my truck , is there any other way to combat this besides carrying extra jets. Any information is greatly appreciated.
Jeff
Freshman User
Joined: Jun 2003
Posts: 35
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From: Colorado Springs, Co
Yes, get better gearing for the rearend, carry a few clothes pins for the gas line
so you don't vapor lock, and watch your temp, that 3.5 really cuts into your
towing ability, 4:10 would be much better, forget the jets, you could set the floats
down about 1/16", that will stop some of the richness your going to have.
so you don't vapor lock, and watch your temp, that 3.5 really cuts into your
towing ability, 4:10 would be much better, forget the jets, you could set the floats
down about 1/16", that will stop some of the richness your going to have.
Senior User
Joined: Apr 2005
Posts: 235
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From: Mobile, Alabama
When I hauled a 10,000 lb trailer loaded with oak firewood - usually three cords - my 1980 F-350 4X4 400 auto 4.10 rear pulled the load with no difficulty once a monster tree downing skid towed my loaded rig out of the "woods" to the highway. That was in Virginia and Southern Maryland at low altitude and with the stock mechanical fuel pump.
Things changed when I moved to Utah. The first time I hauled a heavy load at high altitude, fuel delivery became a vapor lock nightmare. Installing a Carter electric fuel pump under the bed just downstream of the dual tanks solved the fuel delivery problem and I've been hauling my boats - heaviest = 10,000 lbs boat and trailer - with no vapor locking or other fuel delivery problems since installing the electric fuel pump in 1986.
Though a 4.10 axle is ideal for towing, your 460 with your existing ratio should be OK. Diesels and the 460 do well towing with lower axle ratios.
Things changed when I moved to Utah. The first time I hauled a heavy load at high altitude, fuel delivery became a vapor lock nightmare. Installing a Carter electric fuel pump under the bed just downstream of the dual tanks solved the fuel delivery problem and I've been hauling my boats - heaviest = 10,000 lbs boat and trailer - with no vapor locking or other fuel delivery problems since installing the electric fuel pump in 1986.
Though a 4.10 axle is ideal for towing, your 460 with your existing ratio should be OK. Diesels and the 460 do well towing with lower axle ratios.
Post Fiend
Joined: Jun 2001
Posts: 5,228
Likes: 5
From: Running Springs CA
Fuel delivery (vapor lock) is not the only problem. Lack of air density means that your power will drop about ten percent for each 3000 feet above sea level, so 200hp becomes 140hp at 9000ft, even with perfect jetting. The only compensating factor is the cooler air at altitude that slightly increases air density.
Taking off from Big Bear Lake, CA airport in a non-turbo Cessna in summer was a frightening example of this. Even with a manual mixture control and proper leaning, I thought I was going for a swim off the end of the runway.
Jim
Taking off from Big Bear Lake, CA airport in a non-turbo Cessna in summer was a frightening example of this. Even with a manual mixture control and proper leaning, I thought I was going for a swim off the end of the runway.
Jim
Last edited by jimandmandy; Apr 28, 2005 at 10:29 AM.
Laughing Gas
Joined: Jun 2003
Posts: 1,166
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From: Chino, California
Originally Posted by yz250roost
Hey guys,
I wasn't sure if I should post this is my home forum (73-79) or here, so I'll try here first. I've got a 75 F250 with 350 rear suspension. It has a 460 in it without smog (I'm excempt from now on...hooray!!!) My question is regarding altitude towing. I just got the truck and have yet to tow it any long distances. In about 5 weeks we are leaving to go to the Sierra Nevadas, our trip begins at 3000 feet and ends at about 8-9000 feet. I was told that my trucks performance will decrease as I climb higher. Since I don't have all the fancy fuel delivery altering computer stuff in my truck , is there any other way to combat this besides carrying extra jets. Any information is greatly appreciated.
Jeff
I wasn't sure if I should post this is my home forum (73-79) or here, so I'll try here first. I've got a 75 F250 with 350 rear suspension. It has a 460 in it without smog (I'm excempt from now on...hooray!!!) My question is regarding altitude towing. I just got the truck and have yet to tow it any long distances. In about 5 weeks we are leaving to go to the Sierra Nevadas, our trip begins at 3000 feet and ends at about 8-9000 feet. I was told that my trucks performance will decrease as I climb higher. Since I don't have all the fancy fuel delivery altering computer stuff in my truck , is there any other way to combat this besides carrying extra jets. Any information is greatly appreciated.
Jeff
Lower floats to run leaner?? Never heard that one before!
By the way, did you mean (F)-350 suspension or 3.50 gearing?
Remember, Tires sizes will change effective gear ratios. So if they are larger than factory, a 3.50 will not be a true 3.50 ratio. It will be less and less effective.
Jetting on the go is not a good or feasible idea. That stuff is for racers only.
Last edited by pops_91710; May 2, 2005 at 09:42 AM.
Thread Starter
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New User
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From: Santa Clarita, CA
Sorry, There was a confusion when I said 350 rear suspension I didn't mean 3.50 gear ratio, I meant that it's a 1 ton rear suspension. I have 4.10 in the diff.
-Jeff
Thanks for all the help. I've gotta get those 35" tires off the back though, I know that won't help at all.
-Jeff
Thanks for all the help. I've gotta get those 35" tires off the back though, I know that won't help at all.
Laughing Gas
Joined: Jun 2003
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From: Chino, California
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New User
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Another trick for cold high altitude starts is to put a choths pin on the carb butterfly to keep it from closing all the way. reduces flooding and over rich starts.
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From: Home Base Nebraska
Originally Posted by pknute
When I hauled a 10,000 lb trailer loaded with oak firewood - usually three cords - my 1980 F-350 4X4 400 auto 4.10 rear pulled the load with no difficulty once a monster tree downing skid towed my loaded rig out of the "woods" to the highway. That was in Virginia and Southern Maryland at low altitude and with the stock mechanical fuel pump.
Things changed when I moved to Utah. The first time I hauled a heavy load at high altitude, fuel delivery became a vapor lock nightmare. Installing a Carter electric fuel pump under the bed just downstream of the dual tanks solved the fuel delivery problem and I've been hauling my boats - heaviest = 10,000 lbs boat and trailer - with no vapor locking or other fuel delivery problems since installing the electric fuel pump in 1986.
Though a 4.10 axle is ideal for towing, your 460 with your existing ratio should be OK. Diesels and the 460 do well towing with lower axle ratios.
Things changed when I moved to Utah. The first time I hauled a heavy load at high altitude, fuel delivery became a vapor lock nightmare. Installing a Carter electric fuel pump under the bed just downstream of the dual tanks solved the fuel delivery problem and I've been hauling my boats - heaviest = 10,000 lbs boat and trailer - with no vapor locking or other fuel delivery problems since installing the electric fuel pump in 1986.
Though a 4.10 axle is ideal for towing, your 460 with your existing ratio should be OK. Diesels and the 460 do well towing with lower axle ratios.
Denny
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