Topic: 390 saga continues BACKFIRES

[Matt1968]

I'm 2 hours away in NE Ohio, do you have a trailer?

Hey 67 ...no trailer :{ 

Where are you ,  near Cleveland?

[Matt1968]

HI Matt

Give me a call 517 861 7630  (North of Ann Arbor)  It sounds like you know car pretty well -do you think you need a second set of eyes, work together and just confirm correct?

Can you take the time to work on car in one day if planned (or plan a visit and a return if you want to work on it)
Would you need timing light, fresh plugs - have floor jack and stands (clutch) ?
Let me know if you can only work weekends OR if you are avail weekdays (stays light until 9:30).   

Mark Haas
P.S.  I'm not a certified tech, but never met an engine I couldn't start !No cost no obligation - other than a follow up post to inform all.  (good or bad) LOL

Hey Mark ,  I'll give you a call.  I actually took a new job in Taylor and have been commuting.  Looking for a house in Mich right now  AND I'm degreed through Ohio State....gettin' crazy.

[Matt1968]

Time table of "saga"

See original post for background
1000 miles on newly rebuilt engine,  running fine, clutch breaks,  Mustang sits 3 years without starting. 
Pulled dist to oil prime
Won't start. Looked at plug wires.  Somehow plug wires are mis-wired (from engine rebuilder) as compared to ford specs.  Don't understand how it ran like that.
Wired routed correctly now. 
Backfired few timed from carb.
Engine running ok but seems rough
Timing shows way off,  harmonic had to have slipped
Guessing at timing
After starting and running several times,  a backfire out of the exhaust develops (back firing through the exhaust only began after several sessions of 5 minute start and runs). Advancing and retarding,  no change in backfiring.
Today realizing that exhaust backfires are much worse after initial startup then lessen after warmed up,  but still continue.
VIDEO of the backfiring coming soon.

STUCK VALVE?  Dist? Points? Carb?
I can't believe I went from a sweeting running rebuilt engine to this mess.

[Matt1968]

Forgot to mention could this be a muffler issue like one gentleman stated?  I just can't see that being the issue.

[cobrajetchris]

Forgot to mention could this be a muffler issue like one gentleman stated?  I just can't see that being the issue[

I would never believed it either and never considered it, fortunately my father is a retired Ford mechanic (old school) and he was checking it out one day for me and found the problem. The exhaust looked liked new as I stated however it was almost 20 years old with little miles and the moisture over the years rusted out the inside baffles causing the flutter that sounds just like a backfire. Your exhaust may have the same issue from sitting that long. It won't take but a second to confirm or deny.

[67gtasanjose]

Hey 67 ...no trailer :{ 

Where are you ,  near Cleveland?

East of CLE about 50 miles

[Matt1968]

http://sendvid.com/uas90eit

Link to backfiring vid for what its worth.   I seems like the backfires are coming from the drivers side bank.  Also its obvious something is going on in at least on cylinder,  she is not running smooth when revving it....I can feel it.

Next step pulling the plugs (terrible task with this car), then the valve covers.

Matt

[Matt1968]

Forgot to mention could this be a muffler issue like one gentleman stated?  I just can't see that being the issue[

I would never believed it either and never considered it, fortunately my father is a retired Ford mechanic (old school) and he was checking it out one day for me and found the problem. The exhaust looked liked new as I stated however it was almost 20 years old with little miles and the moisture over the years rusted out the inside baffles causing the flutter that sounds just like a backfire. Your exhaust may have the same issue from sitting that long. It won't take but a second to confirm or deny.

Chris let me know if the vid sounds like your muffler situation.

[Smokey 15]

 Plug wires are all run correctly? Distributor is installed in the proper position? Timing is set to specs?  Harmonic balancer has not shifted from dried out elastomer? Plug wires are not ancient and cross firing? You've checked for vacuum leaks? All these things have been covered, right? If not, they should have been.
 If the valve covers are easier to take off than it is to remove the plugs, do that first. Make sure the valves are opening/closing.  A valve could be sticking in the guide and hanging open. Could even be carbon deposits on the valves. If you do remove the plugs, get a bore scope and take a peek inside the cylinder at the valves as long as you're in there.

[67gtasanjose]

ALSO ASSUMING YOU RULED OUT ALL OF THE EASY ITEMS MENTIONED BEFORE~I listened to the video,
This is not an easy of fun thing to do, but try figuring out whch cylinder it if first, on a pre-warmed engine, remove a spark plug wire, one at a time on the left bank. (you could get a jolt here, be careful, they make insulated pliers specifically designed for this...I suggest using them and electricians gloves) If the popping stops, you've narrowed it down. If it gets BETTER, but still popping, you might yet have a crossed wire  Once you narrow it down to which cylinder(s) and you ruled out any possibilty of a crossed wire, THEN, I agree w/ Smokey, pull the V.C. first...look also for a broken valve spring and/or a flat cam lobe.

[WT8095]

What brand of plugs are you using? What heat range?

[cobrajetchris]

If I where you before I remove them miserable spark plugs I would remove each plug wire at the distributer and set it back on but don't click it in. I would run the car for awhile and take a spark plug wire pliers and pull up one wire at a time from the distributer. You should notice a difference in the sound of the engine each time a wire is pulled and if you don't than you have a dead cylinder that could be caused by several things. I would also study the engine vibration when it backfires and see if it misses at the same time. I would not rule out the mufflers either at this point. Do the easy stuff first before you get into the hard stuff. As someone else mentioned I would put a vac. gage on the engine and see how steady the reading is. If you don't have one this is a very good tool to have for little investment. Most vac. gages come with a troubleshooting guide based on the readings.

[GT500KR]

Okay, nobody likes a cliff hanger. My money has been on a sticking valve, or other valve train issue.

Hope you didn't roll it back in the garage and give up?

[67gtasanjose]

Okay, nobody likes a cliff hanger. My money has been on a sticking valve, or other valve train issue.

Hope you didn't roll it back in the garage and give up?

+1...We're on the edge of our seats! 

[Matt1968]

What brand of plugs are you using? What heat range?

Don't remember.  Why would brand and heat have anything to do with it?