Question about 1986 Ford F 350
Posted on May 25, 2011
The vacuum line valve you speak of is just a delay valve and within a few seconds after reaching steady cruise the valve has allowed full vacuum to the distributor vacuum advance capsule so doubt that is the problem. I am a retired Ford dealer service technican and I was working for Ford when this truck was new and watched them age and saw the problems show up as the miles increased, here is what is the MOST common cause of any drivability issues with the 460 V8 equipped with the 4160 series 4 barrel carburetor, (which is a Holley designed carburetor), and that is the carburetor itself, the gaskets leak in the fuel metering plates on the front and rear barrels and dirt gets into the carburetor despite the fuel filter and causes lean fuel conditions and engine surge issues, also the vacuum controlled power valve leaks and causes surging, the cure is a quality rebuild of the carburetor, not a rebuilt unit from Kragen or Autozone, but someone who really knows this Holley designed carburetor and how to properly rebuild them, the book time is 5 hours to rebuild this carburetor correctly, and I've done perhaps a 100 of them. Also other problems with this engine are the intake gaskets leak and the EGR valve leaks at the valve pentile, this allows to much exhaust gas to enter the intake and causes surging as well, so have the intake checked for vacuum leakage and the EGR for proper operation. Also verify the ignitiopn timing is set to 10 deg BTDC.
Posted on May 24, 2011
The carburretor may be leaking a little. The vacuum you need is "ported" vacuum. This means that vacuum is only applied when you are accelerating to aid in advancement of the timing. Whem at cruise there should be little to no vacuum. Centrifugal force (rotating force) will take care of needed advancement while at cruise. Try getting the proper vacuum hose on the distributor and take it for a test drive and let me know.
Posted on May 24, 2011
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Posted on Jan 02, 2017
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