Hello I'm a new member to FTE. I just bought a 64 F250 and it ran like a top till today. While driving it started backfiring thru the carb (2bl) till I let off the throttle. It has a little miss to it at idle, but nothing crazy. I was told that it was a timing issue, stuck valve, vaccum advance, plugs......ect. The vaccume hoses look to be fine, but I think most of the stuff is origional. Has anyone had this problem and what did you do to fix it? I was really hoping to wait awhile to pull the block apart.

 

Bad spring/s resulting in open valves. Could be any of those and you will only find out by looking into it hands on IMO. Check the timing with a light(dont move it prior) see if it is steady, fluctuating mark is a sign of a worn chain, a vacuum gauge will go miles towards a diagnosis. How to Use and Interpret a Vacuum Gauge
Start looking and get back to us with findings.

 

Yep, last time this happended to me was when I tried to get an old truck started after a long sit. Found I had a stuck valve. Good luck.

 

could be a push rod

 

Welcome to FTE! If it were my problem, the first place I would check is definitely timing. I am leaning towards an issue with the advance in your distributor. A stuck weight or broken spring or something. It only takes a second to pop off the distributor cap and take a look.

 

You need to pop the valve covers and check the valve clearance first. Solid lifters will mess with you. If you have good lash clearance then you might have a bad intake valve.

 

My guess is a stuck valve or a burnt intake valve as the Y blocks exhausts are sodium filled and typically do not burn.

Second guess is a wiped lobe on the cam or a broken mushroom tappet.

Third is the timing chain.

Fourth would be the dizzy.

Garbz

 

In addition to checking the timing, don't overlook the point gap and condenser. I had the same problem with my 292. Last thing I checked was the condenser. That was the source of the problem. Problem repeated in about 2 weeks. Yep, it was the condenser again. Truck has run like new for the past several months.

 

Could be any of the above... I hope you don't have the same problem my last 292 had. Ran a compression check and found a dead cylinder. Pulled a head and found it had coughed up an intake valve seat. Never did get that thing fixed.

 

I agree with bob. Use a vacuum gauge to read the problem. If you know how to use one, you can even isolate it down to what cylinder could be causing the problem or dissy sitting OR... I have the original instruction sheet that came with a vacuum gauge I bought many many years ago. If anyone is interested, I could try to scan the sheet and send it to someone that can post it. I don't do posts well. I do believe it explains the use of a vacuum gauge quit well. Just a thought.

As for the popping, you didn't say if its intermittent or constant. It does sound like a stuck valve or very weak spring - back firing through the valve. If it were a weak spring, I would think it would have been doing all the time unless maybe a broken spring. A compression/leak down test would show something. However, I would start with a vacuum test.