87 Ford 460 Carb’d Class C No Power Up Hill

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OldMarine

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Apr 30, 2020
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before ANYTHING, I would do a compression check on the motor...no sense swapping timing chains, etc...before knowing if the thing needs a rebuild.
 

Ex-Calif

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May 15, 2020
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Good advice so far.

The tank filling and pressuring is something to have looked at and it could be part of the problem. If fuel pressure is low you could be draining the float bowl under high load - also helps explain the momentary power cut outs under load. I am pretty sure you don't have a timing chain type mechanical issue but timing is definitely important as are vacuum leaks, however they would also result in bad idling and other side effects.

1/ Have the timing checked accurately
2/ Have the fuel pressure checked
3/ Have the vacuum system checked
4/ Have a compression check done

Barring other complications these seems like it could be a low compression problem. How many miles are on the engine? Does it smoke at all? Is it using much oil? Is the interior of the exhaust pipe black and smoky?

There should also be a crankcase venting system. Usually from a valve cover that routes to a PCV valve or something that dumps those vapors into the intake of the engine. With the engine warm you can remove the pipe and observe if excessive pressure or blowby exists. It's an experience and judgment thing and its pretty subjective. A compression test (especially differential test) will tell you a lot and the differential test will tell you if it is valves or rings.
 

billwild

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Dec 8, 2009
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Had an old 1972 Chev truck that did the same thing when removing the gas cap. I replaced it with a vented gas cap and problem solved
 

billwild

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You mentioned you replaced the spark plugs in your 87 460 Class C. Wasn't that fun. I tried on my old 87 460 class C and after 5 hours still could not get 1 hard to reach plug changed. I now have learned you have to jack up one side of the motor to get that plug changed.
 

TheBar

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Jun 25, 2018
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You mentioned you replaced the spark plugs in your 87 460 Class C. Wasn't that fun. I tried on my old 87 460 class C and after 5 hours still could not get 1 hard to reach plug changed. I now have learned you have to jack up one side of the motor to get that plug changed.
It does make you wonder if anyone actually designs the engine bays on RVs. It took me an hour to find I could fit a short spark plug socket that has 6 flats on the top so you can use a box end wrench to turn it. That eliminates the socket wrench handle and 1/2" of space required. That just fits between the engine and engine bay although you only have vertical space to go 1/6 of a turn before re-positioning it each time. Then when fully unscrewed you find there isn't enough room to take the plug out with the socket attached. So you have to screw the old plug back in enough to remove the socket. I could only get two fingers on the plug at a 90* angle to the hole. Getting the threads started with 2 fingers requires the patience of Job. So it is still a 3 hour job with a lot of cursing involved.
 

8Muddypaws

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Jul 18, 2014
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Check for intake manifold leaks.

with the engine idling spray water (from a squirt bottle) around where the manifold & head meet. Also any hoses that go into the manifold or carb. If the idle changes you've found a leak.
 

JasonJ400

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Aug 16, 2018
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I had what sounds like the same issue with my 1978 28' Holiday Rambler with carb 460. It would start to sputter and die going up big hills on hot days. The issue was with the fuel tank in the back of the rig, going up hill, the fuel pump could not keep up with the carb if you were into the secondaries and it would run out of gas and the heat from the engine would start to boil the gas in the carb and line and BAM vapor lock. The issue is aggravated by heat and altitude. It would not start until it cooled enough for the vapor to unlock. My plan was to put a small 12V fuel boost pump for a generator in the line in the back towards the tank. Other people have just bit the bullet and installed EFI throttle body system. I sold my 78 for a 96 fuel injected Damon and that thing runs like a champ with plenty of power on the larger 30' rig (EFI 460). So I never installed the fuel pump. I also use to keep the gas cap cracked because I suspected clogged vent but it was only an issue on long hills or if you went over 55 for a long time and it started to run hot if you were into the the 4 bbls for a long time on a hot humid, low HG day.
 
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