Exhaust popping, smoke from pack nut, sound from exhaust.

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Model T Ford Forum: Forum 2018: Exhaust popping, smoke from pack nut, sound from exhaust.
Top of pagePrevious messageNext messageBottom of page Link to this message  By John Annaian - Moultonborough NH on Saturday, June 30, 2018 - 09:10 pm:

Wondering what could be causing the exhaust to pop every couple seconds when idle after starting. Theres a gentle pop, and a little bit of smoke comes from the pack nut. Once I start driving, the popping stops. Once I idle after driving it for a minute or two and put it in neutral, there's no popping any more that I am aware of. I think that the pack nut isn't on fully, I can see it rotate in small increments loose. Does that sound like it is the root of the issue? Will it go away once it's fully on? I'd check, and it's probably obviously the issue but I have work early tomorrow and can't really check.

Also, I notice that 80% of the time after shutting it down I hear a FWOOOP from the muffler. I am assuming that's a backfire? I put the car in a fast idle for a couple seconds and then switch to off, leaving levers where they are. I think mixture is about 1 1/4 open ish. Any less and it starts to run rough, I believe this is because this car hasn't been driven for decades and needs to be broken in some more before adjusting it much. Does this sound like too rich mixture or am I needing to do a different shut down procedure? Out of the 10 times it's started, only one or two times it did not make that sound.

1927 T. Rebuilt coils. Rebuilt carburator. New exhaust manifold and exhaust. New rings and glands. New wiring. Rebuilt switch. Charged battery.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Dick Fischer - Arroyo Grande, CA on Saturday, June 30, 2018 - 10:30 pm:

Hi John,

From this and some of your prior posts, I seem to be hearing symptoms of a too lean mixture on initial startup.

Over the past 60 or 70 years, drivers have had the benefit of automatic chokes and have become less aware of the need to enrich fuel mixture on cold startup. And more recently, electronic fuel injection keeps the engine running at the optimum mixture at every stage of warm up.

That soft popping (backfiring) in the intake or exhaust is usually a sign of a too lean mixture, which burns so slowly that there is still flame in the cylinder when the intake valve opens and admits more combustible mixture. Ditto the symptom that you described wherein the engine repeatedly starts and then stumbles and quits after a few seconds.

Choking isn't just to put fuel into the system prior to starting. The operator needs to continue to hold the choke partially out for some time after startup. It's not how many turns you open it; it's how the engine sounds and feels that will tell you when the enrichment is adequate.

Don't be afraid to turn the mixture knob out enough to keep the engine running. Then after a few minutes, as the engine begins to warm up and improve its fuel vaporization, you will begin to see black smoke coming out the exhaust and feel some loping at idle. That's when you can begin to turn the mixture knob in.

As you begin to drive the car (cold), you may feel hesitation when advancing the throttle. That's just another sign of leaning the mixture too soon.

Think of yourself as rediscovering a lost art.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Charlie B actually in Toms River N.J. on Saturday, June 30, 2018 - 10:32 pm:

OK popping out the exhaust pipe is an exhaust valve sticking (I believe) when the motor is cold and apparently freeing up when warm. If the pack nut is loose tighten it by all means.Your exhaust popping smoke from the nut probably means it is loose and/or the pipe flange is shot. Your shutting down method is what's giving you the muffler noise. Idle it down and return the levers to the start position before shutting off the key. You're charging the muffler with fuel then killing the ignition. As to the needle adjustment: 1 1/4 turns is OK but you need to adjust it for best running position after the car warms up. At idle with the spark retarded rotate it for best running.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Erik Johnson on Saturday, June 30, 2018 - 10:38 pm:

Don't race or run the motor at a fast idle as part of your shutting off process. That just loads the motor and muffler with fuel after the ignition is shut off.

Let the motor idle down and then shut off the ignition.


Top of pagePrevious messageNext messageBottom of page Link to this message  By John Annaian - Moultonborough NH on Sunday, July 01, 2018 - 06:12 am:

Great, exactly what I needed! Somewhere I was reading on here to put it in fast idle and kill it and it would load the cylinders with gas which might give a free start or something? I don't know. I'll start to set them back to starting position though.

I had been adjusting the mixture a bunch as I drive and it seems to be happy at around 1 3/4 - 1 1/4 range. But rides have only been 10 minutes long. Once I get my license plates I'll start going on some longer ones and can experiment some more.

I'll tighten that pack nut up today!

Thanks guys. My first T so still learning. :-)


Top of pagePrevious messageNext messageBottom of page Link to this message  By Mark Strange - Hillsboro, MO on Sunday, July 01, 2018 - 07:16 am:

https://www.modeltford.com/item/3061L.aspx


Top of pagePrevious messageNext messageBottom of page Link to this message  By John Annaian - Moultonborough NH on Sunday, July 01, 2018 - 07:56 am:

Ordered it already, thanks though for the suggestion! Backordered :/


Top of pagePrevious messageNext messageBottom of page Link to this message  By Dallas landers on Sunday, July 01, 2018 - 08:06 am:

Loading the cylinders with fuel on shut down will also thin the oil as the fuel goes past the rings after sitting for a bit.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Larry Smith, Lomita, California on Sunday, July 01, 2018 - 09:19 am:

One thing I've noticed, few people have pack nut wrenchs, and even fewer know how to use them properly.


Top of pagePrevious messageNext messageBottom of page Link to this message  By James A Bartsch on Sunday, July 01, 2018 - 10:08 am:

Larry: Please explain how to 'properly use' the Model T exhaust pack nut wrench? Don't you just tighten and loosen as desired?? jb


Top of pagePrevious messageNext messageBottom of page Link to this message  By ROBERT BERGSTADT on Sunday, July 01, 2018 - 02:59 pm:

I have the locking clamps in stock, Bob


Top of pagePrevious messageNext messageBottom of page Link to this message  By Dan B on Sunday, July 01, 2018 - 04:05 pm:

Using the pack but wrench is the only way to get the nut as tight as it needs to be! No clamp needed!


Top of pagePrevious messageNext messageBottom of page Link to this message  By Dick Fischer - Arroyo Grande, CA on Sunday, July 01, 2018 - 05:11 pm:

"Using the pack but wrench is the only way to get the nut as tight as it needs to be! No clamp needed!"

OK, I'll show my ignorance and ask the question: What's the difference between using a pack nut wrench versus using some other appropriately sized open end or even a nice, large crescent wrench?


Top of pagePrevious messageNext messageBottom of page Link to this message  By John Annaian - Moultonborough NH on Sunday, July 01, 2018 - 05:17 pm:

I think the pack nut wrench is a specific size that makes it so you can only apply a certain amount of torque, making it so you can't over tighten it?


Top of pagePrevious messageNext messageBottom of page Link to this message  By James A Bartsch on Sunday, July 01, 2018 - 05:27 pm:

Larry?????


Top of pagePrevious messageNext messageBottom of page Link to this message  By Kenneth W DeLong on Sunday, July 01, 2018 - 05:42 pm:

To tell the truth i do not know how to use the pack nut wrench properly!For close to 50 years i have had a 15" 18" and a 20" adjustable wrenches.I have no need of a pack nut wrench!Bud in Wheeler Mi.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Hal Schedler, Sacramento on Sunday, July 01, 2018 - 05:52 pm:

When you tighten that exhaust nut, keep in mind what you are tightening against. I have never broken a manifold hold-on clamp but I also don't over tighten that big nut.


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