ford 390 engine help

[71PA_Highboy]

Vacuum Modulator/hose on the the C6....

Vacuum tree on the the intake, brake booster.

When looking for a vacuum leak make sure you check the hoses VERY carefully. Also pull the booster hose (if so equipped) to ensure the booster isn't creating a leak you may not be able to see or hear because of engine noise.

Also, WD40 doesn't work as well as it used to... they stopped using a flamable propellent. I like to take a MAPP gas nozzle (the one for oxy-Mapp) and use it... you can really pinpoint the leak (if it exists) and not have the spray mess of carb cleaner.

hth,

eric

[tgbulger2]

okay put the stock carb. back on and truck runs great with the exception of a back fire when at 10 - 12 btdc and it jumps time when sticking it to the floor. i think that this is telling me that the vacuum advance is bad. what is your guy's opinions??....
cause i will set the timing at 10 - 12 ill get the back fire and it will drop down to almost 0 or tdc and when sticking your foot in it it will try to drop more.

[BobbyFord]

Disconnect the advance and set the timing at 10 degrees and see if it still has the problem with the advance disconnected.

[Wes]

These symptoms you describe, are classic point plate sticking. Pull the cap and either use a vacuum pump on vac advance, or push the arm by hand and see if sticks. If not to bad you can clean and lube. If severely worn a new/used dist is needed. Vac pump will check vac advance. While there inspect the mechanical advance under the point plate. Grab rotor turn till stops let go, should snap back. If rotor doesn't snap back the mechanical advance needs service.
Hope that helps

[tgbulger2]

BobbyFord
thank you for your tip. runs great without the advance hooked up.

and

Wes
thank you for your tips. the rotor does snap back so that is still in good condition. but the advance is the problem. with the advance hooked up it back fires and changes the timing. right now it is about 6 to 8 btdc and is running great with the exception of a little coughing at turn off. as i said before new advance is 30 bucks and new rebuilt distributor is 33 bucks. so for the money differ. i will probably put a whole new distributor in. thanks a million with all of the feed back on helping me get the motor running pretty much great. you guys are awsome.