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rarmer
New User
Mar 11, 2014, 6:46 AM
Post #1 of 4
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We have a 1987 Ford 460 automatic in a Motorhome (Tioga by Fleetwood). it runs OK until you hit 55 mph then it starts cutting out and back firing. it will not go over 55 mph (up hill or down). So far we have put in a new carburetor, changed the fuel filter, rotor, distributor cap, plugs, wires and check the timing, and have flushed out the fuel tank with a pressure washer and air hose to make sure there wasn't anything in the tank.. Any idea on what else our problem could be??
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kev2
Veteran
Mar 11, 2014, 6:53 AM
Post #2 of 4
(3473 views)
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Re: 1987 Ford 460
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basics
Using a vacuum gauge - see if there is an exhaust back pressure issue. Need instructions?
Observe that the Carb linkage, is going full open- 'butterflys' opening?
- there were some governors used on these carbs - let us know which model.
You did the fuel filter - might want to look at pump for pressure & volume
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Tom Greenleaf
Ultimate Carjunky
/ Moderator
Mar 11, 2014, 7:01 AM
Post #3 of 4
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Re: 1987 Ford 460
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? "Backfiring" That would prompt me to check valve timing or maybe distributor shaft and gear not common but can slip on roll pin.
Timing chain at the age is in question to me. I'd check (engine off) with timing pointer right where you can see it at TDC and see how many degrees it can be turned by the crank bolt before distributor rotor turns. Get chain tight by turning one way then the other. If you see 5 degrees lost that's a reason to investigate - trust me,
T
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Hammer Time
Ultimate Carjunky
/ Moderator
Mar 11, 2014, 7:19 AM
Post #4 of 4
(3466 views)
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Re: 1987 Ford 460
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If you are getting backfiring, that will pretty much eliminate exhaust back pressure. It sounds like it getting fuel starvation at those speeds. What you have to remember is that electric fuel pumps push fuel but the mechanical fuel pump used with a carb suck fuel so if you have any rotted fuel lines anywhere, either metal or rubber, it will draw air instead of fuel but never leak.I would test the fuel pressure and volume at the carb to see what you have.
Another way to confirm this is to use a 5 gallon can of fuel in the van with you and hook the line directly to the fuel pump so it draws from the can and road test it that way. If the problem is gone, replace all the fuel lines.
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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.
(This post was edited by Hammer Time on Mar 11, 2014, 7:21 AM)
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