Backfiring and cutting out

[Always Learning]

I think my engine is having a major issue with an engine oil treatment I added. I have a 72 F100 with a 351C in it and the other day I changed the plugs, checked the timing and points. Then added a bottle of "Bar's Leak" engine repair, 2 part formula. After letting it warm up for about 10 minutes she was running a little sluggish but no real issues. I drove about 3 miles and filled the tank. About a quarter mile after leaving the gas station she started cutting out and the engine died. When I started her back up, I had to constantly feather the gas to keep her running. After a minute of feathering she seemed to run okay as long as I kept the RPM fairly high, no exact numbers no tack. Then about a mile later she started cutting out and back firing.
I added Heat to see if it was watery gas and changed the plugs again, checked the timing and points. Now I can get it to start and idle, but if I add any tourque to the engine she starts cutting out and backfires. My guess is that the "Bar's Leak" has gummed things up and is causing the valves to stick.
Does anyone have experience with this stuff and/or ideas of how to fix it without pulling the engine apart?

[Supermike]

Sounds more like maybe a fuel starvation issue? Have you changed your fuel filter recently or checked to make sure you don't have a collapsed supply line?

[fordman]

where did this bar leak go into? the water? oil or fuel. bars is known for making radiator stop leak that is why i am asking.

[Supermike]

where did this bar leak go into? the water? oil or fuel. bars is known for making radiator stop leak that is why i am asking.

Sounds like it was this stuff:

http://www.amazon.com/Bars-Leaks-1000-E ... 347&sr=8-1

[Always Learning]

Supermike's image in the stuff I put in and it went into the oil, not the gas or water. I changed the fuel filter last summer and was driving the truck 2 days before I added the Bar's.
So, how would fuel starvation lead to backfiring?

[Supermike]

My honest answer is that I don't know WHY fuel starvation can cause backfire, but I know that it is a SYMPTOM of it. Hopefully someone here can clarify better for you...

[fordman]

when you say you checked the timing and points how did you do it. what adjustments if any did you make?

[Always Learning]

I didn't need to adjust the points they were right on. The timing was a little off when I checked it before adding the Bar's, so I adjusted it a few degrees.

[fordman]

put it back to where it was at and try to drive it again.

[ArizonaDan]

If adding the Bars-Leak is the only mechanical change you made to your engine and your problems began immediately after this then I would be led to suspect there is a connection between these two events. I can't imagine how an oil treatment could directly affect carburetor performance or cause mechanically actuated valves under around one hundred pounds of force to suddenly "stick," but just because I don't understand something doesn't mean it's not possible. If all of your problems began soon after pouring the Bars-Leak into the crankcase then I would immediately re-drain the engine oil and Bars-Leak. Refill with new oil and filter and see if things improve.

However, since backfiring is typically caused by incorrect timing settings or poor carburetor operation it is possible that your performance problems are coincidental to the Bars-Leak treatment. Just your bad luck.

Start with the most probable: you added an oil treatment and engine performance immediately suffered. So, get the oil treatment out of the engine and see what happens. If that does not solve the backfiring issue then continue troubleshooting timing issues, carburetor performance and vacuum readings. Timing advance mechanism in distributor could be sticking in an advanced position causing premature ignition. Key word is could.

Good luck

Dan

[sandmanf250]

is it backfiring out the carb or the exhaust?

[cep62]

If adding the Bars-Leak is the only mechanical change you made to your engine and your problems began immediately after this then I would be led to suspect there is a connection between these two events.

He also filled the tank. I'd check fuel flow.

[1971ford]

That was actually Ford's idea to put the drain plug right above the crossmember. I have seen a few posts on this with pictures of what people have made to get the oil straight into a jug. I believe some use old milk cartons and such as a custom funnel.

[wildcard]

My is with fordman on the timing. I'd move it back to where it was first and try that. Off timing can cause backfiring and running problems. Been there, done that.

[BobbyFord]

You said you changed the plugs...remember, Cleveland firing order is 13726548, not 15426378.