Hello all, I was just cruising down the highway a little while ago in my '26 open touring doing about 35 mph on mag a short distance from home, everything seemed normal until there was one single backfire, i slowed down then continued to my destination a few blocks away, but noticed my new muffler (only had about 20 or so miles on it) had gotten louder. drove home with no problems, car ran fine. took a look and saw that my muffler had blown apart at the seam!!!! does anyone have any idea what could have caused this single backfire strong enough to blow a new muffler apart? I am a little leary to order and put another one on until i find out what the problem could have been! anyone have this experience before? thank's
intermittent ignition switch.
Anyone correct me if i'm wrong but a back fire in the muffler would be from an unexploded mixture of fuel the gets as far as into the exhaust piping and then gets ignited causing an explosion out of the engine cylinder.. So at some point Dennis's engine let unexploded fuel through the exhaust manifold.Then gets ignited via carbon spark or a timing issue like a sluggish valve or crap caught in the valve seat . An Engine cylinder had to miss a beat at some point or a valve stuck open .Dennis, you didn't notice any little engine jerk or hesitation?
My food for thought?
Or as Dough says...A moment of none ignition(bad switch ) that lets unburned fuel in the exhaust then the ignition kicks in again,BANG!...You had to have felt a jolt prior the bang.
Dennis make sure your needle valve isn't set to rich
I once made a right turn with a finger of my left hanging down. When I turned the wheel my finger pushed the spark lever all the way up and blew the muffler apart. That was loud!
That is usually caused by a bad ignition switch. It could be a loose connection anywhere from the magneto to the coil box. It doesn't usually happen with just one missfire, but if all cylinders misfire, and then ignite, the exhaust will be hot enough to ignite the fuel mixture which was unburnt in the muffler. It can also happen if you are driving along and you switch from mag to batt or from batt to mag.
You can fix the muffler. The metal was crimped together from the factory. It can be welded and the ends can be tack welded in place. They tend to fall apart anyway, and the tack weld will help.
Does your muffler look like this ???
Since the supplier couldn't get a new outer shell, since I couldn't get mine back together. I had mine welded up at a muffler shop.
I had the seam welded at the entrance area all the way up the outer shell seam. At the same time I bored two more holes in the middle shell and enlarged the exit oval hole so there wasn't as much back pressure. Little louder but not much and car breaths better for this car. Still has that nice perking T sound.
Do add a locking nut , lock-washer doesn't work for me.
Thank's for the response! It could have been any of the suggestions now that they have "jarred" my memory! I was on a straightaway and shortly prior to the big bang (which scared my wife half to death!) I opened the mixture just a notch because the rod has a tendency to be loose and I noticed it was just off center where it seems to run the best (i should have kept my mitts off it because the car was running fine, just seemed a hair sluggish!) I also just put kevlar bands in her about a week ago (after a miserable 2 week experience of trying to get them out and in and out and in again!!!), so I could have messed up the connection from the magnito inadvertently!!!
and thirdly, i was tinkering with the dash light switch trying to get it to work a few weeks ago and had the ignition switch out making sure the connections were tight!!!! So I guess it could have been any or all of the above suggestions that you guys gave me!!!!!!!! I will have to go over each one tomorrow and make sure everything is right!!!!!! Thank's much for the ideas!!!!!!!!(could have been a "perfect storm"!!!!combination!)
I have routinely pulled the spark lever to full retard while driving. That should never cause a backfire since you are simply delaying the onset of the spark and not disabling it. I am not doubting you had a backfire but I don't see how moving the lever could have skipped a spark event since the furthest you could have moved it was to about 4 degrees AFTER top dead center. The lever has no way to completely shut off the spark event. That one is a puzzler.
George, I am curious,my muffler did split apart at the seam but not as bad as yours did! The thing i am curious about is that almost from the time i installed it brand new about a month ago, when i started the car i could "smell" the metal getting hot and it started to get dark blue almost like a motorcycle exhaust pipe gets when hot, then within a very short time (after a couple of short drives) it was coated with a dark surface rust,(i'll post a picture tomorrow), How is it that the metal on your blown apart muffler still looks like new?
Hi John, how have you been? I am just about positive that the spark lever did not move, (have not yet had a backfire while driving the car since i relined the gas tank years ago and got all the rust out which was causing fuel starvation) the only time she has backfired at all is a couple of times when shutting it off ( but i can't even remember the last time that happened!)
Just out of curiosity Dennis, where did you get your new muffler? Was it Sacramento Vintage or Gas light by any chance?
If your exhaust system is running very hot, that is a symptom of of running too lean. It you run at night you can easily get you exhaust manifold and pipe glowing red just be leaning out the fuel mixture.
Dennis, it was new and it does show a little blue. I was haveing trouble starting and keeping it in time. Discovered that the spark control lever had loosened up. Always flooded. This was happening after the engine had been driven a bit. First start in the morn was no prob. Turned out the hole thru the spark control rod was all woggled out. Installed new lever, pin and slathered it with JB Weld and let it set up overnite. Retimed and works like a charm.
Intermittent ignition switch or wiring.
Don't forget the some what rare but happens, momentary short out(or completely) of magneto plug. Via a bit of broken safety wire getting slung up to the internal mag post.
You mentioned that you sometimes run with the spark lever all the way up. That would slow the engine and heat the exhaust manifold. Also if you are going down a steep hill and you push the spark lever all the way up, you will get a pop pop pop in the exhaust from gas which burns after the exhaust valve is open. Not a big BANG just many small pops. That couldn't be good for the exhaust valves. I have tried going down hills with the spark lever up or down and the throttle closed. It doesn't make any difference in the speed. I go down hills with the spark in the same position I use for traveling on level.
I can tell a distinct difference in engine braking by retarding the spark. It doesn't give any popping either. It is funny how different cars behave so differently.
Absolutely agree - on steep hills retarding the spark all the way helps a lot.
I have my throttle adjusted so that with the lever all the way up it will barely idle when warmed up, for maximum compression braking.
John, I don't think retarding the spark was the sole cause of the explosion. That happened a few years ago during one of the first drives in the coupe and there were several problems with the car. It did not run well at all.
george, these are pictures of what it looked like when I installed it about a month or so ago, (have only driven short distances since putting it on) the other pic was taken this morning. (after she blew out yesterday)
Martin, It was either lang's or snyder's, i bought a bunch of things to change the bands since then and i can't remember which one it was, but i have never ordered from the two places that you mentioned.
I had the same thing happen about ten years ago. I accidentally turned off the ignition with my foot while going about 20 MPH in my '15. Reached down and turned it on BABOOM saw the outer muffler shell in my rear view mirror rolling down the road.
Dennis, Mine blued up and rust fast also. So when a new Muff. came I made some changes. I found that the new muff. was too restrictive for flow, I running 280 cam and Zhead. So I bored two more holes in mid.shell and enlarged the exit. Outer shell welded to exhaust entrance end and welded spotwelded seam. Painted entire muffler with 1000deg header paint. End nut w/ lockwasher kept coming loose so I added another nut as a locknut.
Just a thought, how deep into the muffler should the exhaust pipe enter normally? When I installed this muffler, i was contemplating cutting a couple of inches off of the pipe because it seemed a little long to me but I left it alone because it slid in without a problem. I believe that the pipe was about 2 to 3 inches into the muffler itself not including how far into the little pipe attached to the muffler itself.could it being in too far cause this type of problem? just wondering!
I had to trim a little off the exhaust pipe . I mounted muff. to frame hole and measured and cut excess.
The exact same thing happened to me when I gave the late - great Ken Meeks a ride in my '14 runabout. My big foot accidentally cut off the ignition. When we arrived home he simply turned the key upside-down where it still is today. I liked the idea so much that I did the same on the '15 depot hack
An old Tyme T guy I knew growing up use to make and install four 1" wide flat steel x 1/8" bar stock clamps around his T muffler drums....Now I know why!
That's a good idea Dave, I was just contemplating putting a couple of straps made from that universal gas tank strap with the holes every inch or so, when the new muffler gets here, I think I have a small roll of it in the garage somewhere! Don't think it could hurt anything, and it may save the " thin steel" muffler from literally, "coming apart at the seams" !!!!LOL
once i removed it, there was more damage than i thought could happen from one single backfire, I think it was a combination of a poor quality muffler and the backfire that took this one out, otherwise only the seam would have split, this whole thing blew apart! I have had backfires before with the old muffler that caused no damage at all!! I replaced this one with one that has had the ends and seam re enforced with tack welds, hope it lasts a little longer than this one did!!!!
a video of the car with the new muffler installed just for the heck of it!
I sometimes get a crowd pleasing/startling "BANG!" if I am not brisk enough in switching from Bat. to Mag. when starting the car... the 1927. For some reason I don't do that on the '13. Probably because the key is so long it is easy to grab and turn to the correct position.
I won't put the key in upside down as I like being able to kick the key to "OFF", otherwise I have to set the brake and get out in order to reach the key... my ladder gets in the way, otherwise!
I blew my muffler apart several times before I found the exhaust on father's Mack truck was the same diameter, the Mack exhaust is about 14 inches shorter and the muffler has not been a problem since