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Rough Idling - Is that knocking?
https://www.slantsix.org/forum/viewtopic.php?t=62944		 Page 1 of 1
Author:  dratsum [ Sun Oct 21, 2018 10:01 pm ]
Post subject:  Rough Idling - Is that knocking?
Hi everyone - My wife is the owner of a 69 Barracuda Mod Top with the Chrysler 255 slant 6. It was her first car, her dad bought it for her. Anyway, she isn't a daily driver - we live in Brooklyn and really only take her out when we go out of town or to get groceries - but I've noticed a few things off with her that I would like to try to learn to fix. I'm pretty technically adept, but I don't know much about working and tuning old cars. I'll start with the most immediate issue. She idle real rough, and has stalled a couple times. Doesn't seem to matter if it's cold out or not. Seems to be worse in D or N rather than P. Also, I her a kinda high 'tink' sound from the motor - not sure if that's a knock or not. It's the single barrel carb. I recorded some videos -- could you guys help me diagnose the issue? I want to learn how to keep this baby running well.

This is showing the fuel economy gauge while idling: https://youtu.be/p1TadmvI6KE
And this is a video of the motor: https://youtu.be/5dmuJJQrdUE

thanks /b
Author:  DadTruck [ Mon Oct 22, 2018 8:11 am ]
Post subject:  Re: Rough Idling - Is that knocking?
I watched both videos,
Idles a little bit rough, but not bad. Sounds like a bit of
piston slap from the slow, uneven idle.
When was the last time the motor got a full tune up?
New spark plugs, wires, distributor cap, rotor and points.
Ignition timing checked...and verify the motor oil has been
changed recently and the fuel is fresh.
You should also check the valve lash, that plastic fuel filter
should be repaced.
You should conside a complete carb cleaning and rebuild.
This may seem like a lengthy list, but if you don’t know when
These items were done, it is time to address them.
Author:  dratsum [ Mon Oct 22, 2018 12:27 pm ]
Post subject:  Re: Rough Idling - Is that knocking?
Quote:
I watched both videos,
Idles a little bit rough, but not bad. Sounds like a bit of
piston slap from the slow, uneven idle.
When was the last time the motor got a full tune up?
New spark plugs, wires, distributor cap, rotor and points.
Ignition timing checked...and verify the motor oil has been
changed recently and the fuel is fresh.
You should also check the valve lash, that plastic fuel filter
should be repaced.
You should conside a complete carb cleaning and rebuild.
This may seem like a lengthy list, but if you don’t know when
These items were done, it is time to address them.
Thank you for the help DadTruck- the motor got a tune up about 6 years ago, but I had a mechanic do it and I'm can't be 100% sure he did everything you listed. He did rebuild the carb, and I believe he put on a new distributor cap - but I can double check that. Oil is clean, changed maybe 1200 miles ago. Fuel is fresh, just went through 2 tanks on a road trip two weekends ago. I feel like checking the valve lash might be more than I am capable of doing myself, but I should be able to change the fuel filter -- can you recommend a brand?

Do you think a carb adjustment might help?

best/D
Author:  DadTruck [ Mon Oct 22, 2018 2:36 pm ]
Post subject:  Re: Rough Idling - Is that knocking?
for a fuel filter, any brand that is in a metal can would be fine, you certainly can't go wrong with a Wix filter

for the carb, if it was fully rebuilt 6 years ago, no guarantee but it should be good

for the points, plugs and spark plug wires, after 6 years new ones could not hurt, check the rotor and distributor cap,
if the internal terminals show burning or wear, change them also, a PCV valve should also be on the changeout list.
check ignition timing.

If you do change out the sparkplugs, the color - condition of the old ones can tell much
about the motor. Keep the plugs in order and post a photo, some one will respond

certainly a proper valve lash check and adjustment should be done
there are several good articles on this forum on how to do that.
check them out, ask questions if you are not sure.

Consider learning how to do valve lash, and changing points and other basic tune up
processes yourself. In this age of computer controlled cars most automotive techs will
not have any idea how to set valve lash or change ignition points.

for a carb adjustment, the idle sounds a little slow, maybe turn the idle speed up a bit.
Author:  bboogieart [ Mon Oct 22, 2018 5:29 pm ]
Post subject:  Re: Rough Idling - Is that knocking?
I hope I am not being insulting.
Definitely not the intent.

I tune my vintage motors at about 6 months, not six years.
Points especially need constant monitoring,as they wear with use.
Do yourself a favor.
Get some books/manuals on maintaining older vehicles.
I use Chiltens and Haynes.

You will find out more than just the motor needs regular attention, such as brakes, clutch and/or trans, and suspension parts.
Author:  dratsum [ Mon Oct 22, 2018 7:02 pm ]
Post subject:  Re: Rough Idling - Is that knocking?
Quote:
I hope I am not being insulting.
Definitely not the intent.

I tune my vintage motors at about 6 months, not six years.
Points especially need constant monitoring,as they wear with use.
Do yourself a favor.
Get some books/manuals on maintaining older vehicles.
I use Chiltens and Haynes.

You will find out more than just the motor needs regular attention, such as brakes, clutch and/or trans, and suspension parts.
Not insulted. We live in the city and use mass transit so the car really doesn't get driven much - so - 6 years might still be a long time, but she might have only traveled 500 miles during that period. Understand that sitting up comes with it's own problems - we try to fire it up and take it to the grocery store at least twice a month. I've done a bunch of research about the function and operation of the car, but honestly I'm just not super confident and am just afraid I'll ruin something or cause us to die in a fire on the highway :D - - Also, it's not my car, it's my wife's from years before our marriage so makes me even more sheepish about it.

Lastly, any work I do on the car myself is going to be done in a parking lot or on the side of the street - we have a covered parking for the car, but we don't have a garage where I can work on it. So that limits things a bit. Which is why most of the work we've done on it has been done by a mechanic - breaks, alternator, belts, etc.

But - I've always really wanted to be able to do more my self than changing the oil - so - I thought maybe by taking on seeing if I can get the motor running a little smoother, I could help gain a little more experience and confidence before I try to do something like a super six upgrade by myself. Thanks for the manual recommendation! I've tried to pick up a Haynes for it at my local AutoZone and they never have it.
Author:  Charrlie_S [ Tue Oct 23, 2018 3:23 am ]
Post subject:  Re: Rough Idling - Is that knocking?
Quote:
I've tried to pick up a Haynes for it at my local AutoZone and they never have it.
Actually, a better solution is a factory service manual. They can be found on E-bay, or downloaded here.
http://www.mymopar.com/index.php?pid=109

Parts manuals here. http://www.mymopar.com/index.php?pid=107
Author:  bboogieart [ Sun Nov 04, 2018 7:51 am ]
Post subject:  Re: Rough Idling - Is that knocking?
I understand where your coming from. I had to work on my car in the street when I was living in the city, before I could afford a garage for it.
Nice to see you not giving up on it. Once dialed in, it will be a source of great enjoyment for your wife and yourself.

That said, just sitting for that long it will need a lot of maintenance to get it running properly again. Points and fuel will deteriorate just sitting.
So do things like brakes, tires, hoses, steel lines, and what not.

Again I don't want to discourage, just trying to help out.
The factory service manual is a great recommendation.
Myself as a young fella went to the library and copied pages out of the Motors Manual. Was good enough for me to keep things moving along.
This forum will likely be your best source of info.
Didn't have such things in the 70's. :wink:
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