Our Mz Ruby has a driveabilty/tune issue. Any thoughts?

[Dsertdog]

Poor Mz Ruby.
Our 66 Polara 383 4v picked up the shakes. Off idle the engine shakes. Cold , it sounds like a diesel until she clears her head. It's a steady shake too, until I raise the rpm
I checked the choke, idle screws, dwell and idle. Nothing failed or went out of whack, that I can see. the idle isn't fast, nor do I hear air, like a vacuum leak.
Last week I was headed for a cruise across town We put a little gas in her, Same brand, same octane (we hope) but different station.
I noticed a stumble off idle leaving stoplights as we cruised the avenue after parking for little bit.
When I put her in storage Monday night, she sounded awful. Off idle she was chuggin'. No backfires or exhaust pops. Just the shakes.
BTW the shakes disappear at cruising speeds or medium acceleration. They seemed to get better as the car reaches heat sink.
I filled up with premium unleaded at the normal station, and added some gas dry in case the last fill had water in it. I thought the shakes were getting better, but they really aren't.
Fuel doesn't seem to be the issue. Full throttle kick down works fine.
I realize diagnosis by internet can be dicey at times. But what comes to mind? Ignition advance?
Thanks in advance for reading.

 

[Davea Lux]

Start the engine and then turn it off. Remove the air cleaner and look down the carb throat to see if fuel is dripping. If so you have a bad seat on the needle valve or a failing float. I think you may have some crap in the needle valve so check that and report back. Is the car making a lot of foul smelling smoke when it is stumbling? You might also want to pull the plugs and see if any are fouled.

Dave

 

[HWYCRZR]

If I get a little too much advance I will get a mid range shake. ‘68 383 2bbl
Throw a dial timing light on it and watch the rpm and advance ( plug or crimp the vacuum advance for this).
The service manual uses distributor advance. Remember every degree on your distributor is twice as much when read on your harmonic balancer. Same with distributor rpm your engine is double. My 2bbl settings call for a little lower than 4 bb
Below are the ‘68 383 4bbl conversions. May not be exact for 65 but get you in the ballpark for troubleshooting.
Between 750 -1050 engine rpm you should not get any extra mechanical advance from your base setting (5 degrees for 4bbl (68 spec for example)
At 1050 engine rpm it is within spec if you have 0 - 13 degrees advance above base (5 base +13 =18 total)
At 1520 engine rpm you should have between 20.2 & 24.2 degrees advance above base ( 5+ 20 to 24 = 25 to 29)
At 5,000 engine rpm you should be sitting at 29 - 33 degrees above base (5+29 to 33 degrees = 34 to 38 degrees total).
If your advance springs are a little weak. You will advance faster than you want. If you are running high enough octane and good quality fuel you may not get as much pinging but will run rough.
Rule out your base timing and mechanical advance first.

 

[Davea Lux]

And if you timing has jumped unexpectedly, be sure to check the timing chain for excessive slack.

Dave

 

[HWYCRZR]

It is also amazing what a little sea foam added to your gas will do to clean up light carburetor gumming.

 

[57fury440]

How long since the last time you drove it? Could it just be bad gas?

 

[Dsertdog]

How long since the last time you drove it? Could it just be bad gas?

A couple other people off line have suggested bad gas. I bought gas from a station I have never bought from before. This was a week ago. I filled the tank from my normal vendor today. It's a station that most of the hot rodders on my end of town use.

I'll be driving the car to Joplin tomorrow. If it was bad gas, I'll be burning it out!

 

[Dsertdog]

Well...
Miz Ruby's running a little better, but not perfect.

Today I hooked up my timing light. Initial timing is still where I set it last year. It bounces just a hair, so I'll be checking timing chain slack. I know the bushings were just inside max spec.

I checked the advance and it worked...because there's no load. Then I clamped off the vacuum hose to the vacuum advance.

I have almost no mechanical advance. Zero, zip, nada. Timing mark barely moves. Maybe a 1/4 inch off initial. That's not enough for the rpm it was turning

Once I get the A/C compressor out of the way, the distributor will be coming out for a rebuild.

Thanks @HWYCRZR for the advance specs. I believe those might be in my FSM.

 

[Davea Lux]

You might also try putting a few drops of oil on the felt under the rotor, that will put some lubricant down the shaft and it might free up the mechanical advance.

Dave

 

[Davea Lux]

If you have the A/C unhooked, put some tape over the connections to keep water vapor from entering the system. Water vapor will turn the refrigerant oil to jello and make it very difficult to remove. The oil needs to come out prior to converting the system to run on R-134a because the R-12 oil is not compatible with R-134a and will turn into something approximating gorilla snot.

Dave

 

[twostick]

Well...
Miz Ruby's running a little better, but not perfect.

Today I hooked up my timing light. Initial timing is still where I set it last year. It bounces just a hair, so I'll be checking timing chain slack. I know the bushings were just inside max spec.

I checked the advance and it worked...because there's no load. Then I clamped off the vacuum hose to the vacuum advance.

I have almost no mechanical advance. Zero, zip, nada. Timing mark barely moves. Maybe a 1/4 inch off initial. That's not enough for the rpm it was turning

Once I get the A/C compressor out of the way, the distributor will be coming out for a rebuild.

Thanks @HWYCRZR for the advance specs. I believe those might be in my FSM.

Keep in mind if it still has the stock advance springs in it, it will take a good bit north of 3000 rpm to get close to max advance.

That being said the weights can also seize on their pivots. You should be able to twist the rotor clockwise against the spring pressure and make the weights swing out. If they won't, the pivots are seized.

I don't think the distributor advance is your problem tho, at least not at just off idle. It should be more than happy to run there on base timing.

Kevin

 

[Dsertdog]

Keep in mind if it still has the stock advance springs in it, it will take a good bit north of 3000 rpm to get close to max advance.

That being said the weights can also seize on their pivots. You should be able to twist the rotor clockwise against the spring pressure and make the weights swing out. If they won't, the pivots are seized.

I don't think the distributor advance is your problem tho, at least not at just off idle. It should be more than happy to run there on base timing.

Kevin

It was taching about 2 k when I had the wife back it off. I guess I'm used to a quicker advance.

If it isn't the advance what do you think it might be?

You might also try putting a few drops of oil on the felt under the rotor, that will put some lubricant down the shaft and it might free up the mechanical advance.

Dave

I did that last year when I installed new points. The felt disc was so dry it looked like a baked potato chip. Ditto with the oil cap on the side.

 

[HWYCRZR]

If you aren’t getting advance movement at 2,000 something is sticking or stuck.

 

[Dsertdog]

I pulled the distributor out of the engine today.

I could tell something wasn't right. So I disassembled it. Sadly I broke the nylon retaining ring with a mis strike while removing the roll pin.

Sure enough, the advance weights were gummed up and wouldn't move. With the springs pulled, they were still gummy and stiff.
A can of Brakleen later and now they are loose as a goose.

But what's with this advance spring that is so heavy you can barely stretch it. I've no desire to put ultralite springs in the advance but this is ridiculous!
And I need nylon retaining rings...and a couple of thrust washers.
Pic for fun...yes was worse than that!

 

[HWYCRZR]

I pulled the distributor out of the engine today.

I could tell something wasn't right. So I disassembled it. Sadly I broke the nylon retaining ring with a mis strike while removing the roll pin.

Sure enough, the advance weights were gummed up and wouldn't move. With the springs pulled, they were still gummy and stiff.
A can of Brakleen later and now they are loose as a goose.

But what's with this advance spring that is so heavy you can barely stretch it. I've no desire to put ultralite springs in the advance but this is ridiculous!
And I need nylon retaining rings...and a couple of thrust washers.
Pic for fun...yes was worse than that!
View attachment 380731

Primary and secondary. The stiff spring is what keeps it from advancing all the way until you get to higher rpm. First spring ( light) regulates your initial mechanical advance up through about 1500 rpm. If the light spring is too loose or has slack your mechanical will start advancing around idle. You don’t want that. It should start allowing the weights to start going out around 1000 -1050 rpm. Then the centrifugal force starts working on the heavy spring keeping the advance steady up through 5000 engine rpm.
Probably not the best technical description, but in simpler terms.

 

[65sporty]

I pulled the distributor out of the engine today.

I could tell something wasn't right. So I disassembled it. Sadly I broke the nylon retaining ring with a mis strike while removing the roll pin.

Sure enough, the advance weights were gummed up and wouldn't move. With the springs pulled, they were still gummy and stiff.
A can of Brakleen later and now they are loose as a goose.

But what's with this advance spring that is so heavy you can barely stretch it. I've no desire to put ultralite springs in the advance but this is ridiculous!
And I need nylon retaining rings...and a couple of thrust washers.
Pic for fun...yes was worse than that!
View attachment 380731

If you need distributor parts check with @halifaxhops. He rebuilds and can also set a custom advance curve I believe. I know he has Sun distributor machines.

 

[halifaxhops]

I toss those nylon collars they always break usually in the engine. PM me on needs.

 

[Dsertdog]

After installing a new collar from Mopar, which had to be drilled to fit, I installed the distributor today. No shaft play at all now.

Mechanical advance is now functional, but it took a while to get the stubborn stumble out. It was combination of several things. Timing, idle mix and even accelerator pump squirt all had to be puttered with until the stutter all but disappeared.
The effort paid off with a lot more bottom power. Miz Ruby will spin the tires on gravel and wants to spin on pavement now!

There's still an occasional timing flutter. Things are supposed to cool off Wed, so I'm going remove the top of the shroud and the fan and see if I can get a socket on the balancer bolt.

What's the size hex on that bolt? 1-1/4?

 

[HWYCRZR]

Yes 1-1/4.
It is a combination of everything to get a good tune.

 

[Dsertdog]

Yes 1-1/4.
It is a combination of everything to get a good tune.

Computers have spoiled me! Thanks for your help as well!