Sonic boom when starting 63B

[Art Kendall]

Had a shocking revelation yesterday, when I went to start up the 356 which I do every 7-10 days if I am not driving it. After trying a couple times, I had the loudest backfire I had ever heard. After getting out of the car, I can see smoke and soot over the back fender edge.

After researching in the archives to find out why, I can see that the probability of gas in the exhaust system ignited when started.

Shortly after that, I tried again and it started right away. Normally I have not had much of a problem starting it, but lately it had seemed to take more time when cold, so I had recently installed a new trickle charger, so the battery was topped up.

When it started I got out of the car, and could see exhaust coming out the side fenders and not the tale pipe ends. After further investigation I saw that both the exhaust tail pipe had come off the muffler, and the other end going into the exhaust funnels on the bumper had twisted and come out. This was on both sides.

Question. Not sure if the backfire blew off the tail pipe, or the pipes were already off, and this compounded the probability of gas igniting in the exhaust system. Incidentally this is a European exhaust system.

Appreciate any input to figure out what caused what.

Thanks
Art

[Vic Skirmants]

Art; never simply start the engine unless you are going to go for a drive and get everything up to operating temperature.
You are filling the exhaust with condensation and combustion acids, and setting up for an early failure of the exhaust system.

[Art Kendall]

Vic,

Thanks for the advice, even though I have always let it run for 20-30 minutes and sometimes run it up and down my driveway. Will think next time.

Not to be too ignorant, but could that have had anything to do with both the exhaust tail pipes coming off the muffler, or just coincidental? Maybe the clamps were not tight enough on the tail pipe ends?
Art

[Ron LaDow]

Art,
I had a 1720-kitted C and used to drive to a friend's house in SF for horse-shoes and BS, staying there an hour, maybe two. Say a 20 minute city drive, with the car parked on a very steep incline, nose down when there.
For reasons I've never discovered, about every 2nd or 3rd time I'd start it to leave, that thing would light off with enough force that I'd have sworn was enough to blow a hole in the muffler! You could see people's heads popping out of windows up and down the block!
The first time, I got out and looked to make sure everything was still there.
Never did figure it out.

[Dick Weiss]

Art,

If you don't drive the car for @ least a 1/2 hour or more, better to leave it alone until you take it for a long drive/tour..
However, depending on your weather, don't prime the carbs any more than 2 or 3-pedal stabs when cold & no more than 1-when warm/hot.
Also, are the carb "squirt" amounts w/in specs--also are they balanced to each other?
If excessive, it'll load up the exhaust system including the possible loose or lost elbows--during a coast-down when driving--it'll "boom", too.

Dick

[Art Kendall]

Thanks for the input.

Ron, I had that same boom and while I live right in the city of Vancouver, houses are close and the guy at the end of the street heard it. In the 13 years I have owned the car, it has never happened before. I think all of the signs came together on this one.

Dick, some good advice all round and I will change my habits. When cold I have usually done quite a few peddle stabs when cold, and maybe that is part of the problem. An old 356er years ago told me to do that. As I mention in the original post, in the past it wouldn't be that hard to start when cold, but have been noticing it is getting harder. Probably your point about the carbs makes sense and I bet they are not balanced. Will get my mechanic to look at that as I have not messed with them in the past.

So it sounds like from what you are saying that it is possible that the elbows could have blown off with the explosion. Probably you think?

I quickly looked at it trying to turn the pipe around, and it even looked like one of the brackets was bent a bit. Quite a force and I figured I would just take everything a part and put back together.

Guys, appreciate everyone's input.
Art

[Art Kendall]

Art,

If you don't drive the car for @ least a 1/2 hour or more, better to leave it alone until you take it for a long drive/tour..
However, depending on your weather, don't prime the carbs any more than 2 or 3-pedal stabs when cold & no more than 1-when warm/hot.
Also, are the carb "squirt" amounts w/in specs--also are they balanced to each other?
If excessive, it'll load up the exhaust system including the possible loose or lost elbows--during a coast-down when driving--it'll "boom", too.

Dick

Dick,

Do you think it was possible that the exhaust pipes blew off due to this, or it was just coincidental.
Art

[Dick Weiss]

Art,

If the pipe(s) were loose on the muffler, it's possible--if your car is an A series; The B/C series have the extra bracket-clamps
to the muffler to retain the pipes.

Happy Thanksgiving,
Dick

[Thomas Sottile]

most likely the explosion blew them apart. Look at the mounting flange on the muffler to engine. with the engine running check for flame or smoke from the flange you could put a little oil in the carb to help make smoke.

[Martin Benade]

The pipes are not that secure at best, I have lost at least one over the years, with no explosion to help.

[Art Kendall]

most likely the explosion blew them apart. Look at the mounting flange on the muffler to engine. with the engine running check for flame or smoke from the flange you could put a little oil in the carb to help make smoke.

Thomas,

Thomas, thanks for the feedback, and to others.

I am sure the explosion caused the pipes to come off, as there had to be a lot of pressure based on the noise, and soot afterwards on the fenders and ground.

It is possible that the reassembly of the bumper and tailpipes, after I had the car completely painted a few years ago, the guys did not tighten down the clamps the way they should have.

As Dick suggested, I have also been priming too much when cold and will have the balance on the carbs checked.

Hope everyone is having a nice Thanksgiving, and up here in Canada, we celebrate the 2nd Monday in October.

I appreciate everyone's input!!
Art