Meet Snow White, my 1970 N-code Dodge Polara Convertible

[sixpkrt]

Too bad Wyatt is still banned from FCBO @Joeychgo .
We'd like to hear his synopsis of what is going on with the vibration

 

[fury fan]

At that point, the only thing left will be the radio.

 

[ayilar]

Wyatt tell me he has "checked all the normal or obvious things to check." That's why we are at mounts. It's another thing to elimate from the list of possibilities.

It happens in park, in neutral, and in gear. And it is consistent with engine RPM.

Wyatt does not think it's a firing order issue. Snow doesn't miss or stumble, and the engine (which was rebuilt professionally under prior ownership) runs strong.

Flex plate tight, maybe crack? Try undoing all the belts and run it.

Might need to be balanced after the new pistons, I did a quick search of the part number and came up with "OHIO 991P Engine Piston 383
fits model: Std. make: Dodge, Chrysler. year: 1959-71–1963-71."

I guess I have been under the impression the source of the vibration had been traced to the engine but now indicating that the vibration appears above 60 mph in top gear makes me suspect it could well be something else.............................such as driveshaft balance or something similar.......................

Well, quick update here: @cbarge kindly took the car for a one-mile spin with me at the Volo show, and it turns out that the explanation may be quite a bit simpler:

1. the fan was way too noisy, which was the tipoff. @cbarge checked it out, and sure enough the Hayden 2747 heavy duty fan clutch that was installed back in 2020 (less than 200 miles ago) was not spinning freely. So, the fan clutch needs replaced;

2. when driving shotgun with @cbarge, he pointed out that the accessory belts were squealing under his heavy acceleration (he pushed on gas much harder than I had tried when bringing Snow from the alignment shop to the Volo show -- after his debugging Medina 3 years back, I think I see a pattern in his approach ). I also smelled some "burning metal" after he pushed hard (I had not smelled anything when @fury fan and I had driven, much more gently, a few miles to Volo). Turns out that:
a. the A/C compressor seems to have bearings that are on their last leg, and the compressor is not spinning freely -- so it needs replaced or removed;
b. the dual accessory belts, which I had bought back in 2020 and were supposed to be the right ones for the car, look ever so slightly too wide for the pulley's grooves -- the net result is that one of the belts is fraying at the edge, and so I did not drive Snow back from Volo (out of an abundance of caution, and at the recommendation of @cbarge , I had the car flat-bedded back to Wyatt's shop). So, we need to check that the pulleys are correct and that the belts fit exactly.

@71Polara383 can fill in more details, but hopefully this will be the explanation. Here is a photo of Snow White on the tow truck.

 

[saforwardlook]

Well, quick update here: @cbarge kindly took the car for a spin with me at the Volo show, and it turns out that the explanation may be quite a bit simpler:

1. the fan was way too noisy, which was the tipoff. @cbarge checked it out, and sure enough the Hayden 2747 heavy duty fan clutch that was installed back in 2020 (less than 200 miles ago) was not spinning freely. So, the fan clutch needs replaced;

2. when driving with @cbarge, he pointed out that the accessory belts were squealing under heavy acceleration (harder than I had tried when bringing Snow from the alignment shop to the Volo show). Turns out:
a. the A/C compressor seems to have bearings that are on their last leg, and the compressor is not spinning freely -- so it needs replaced or removed;
b. the dual accessory belts, which I had bought back in 2020 and were supposed to be the right ones for the car, look ever so slightly too wide for the pulley's grooves -- the net result is that one of the belts is fraying at the edge, and so I did not drive Snow back from Volo (out of an abundance of caution, and at the recommendation of @cbarge , I had the car flat-bedded back to Wyatt's shop). So, we need to check that the pulleys are correct and that the belts fit exactly.

@71Polara383 can fill in more details, but hopefully this will be the explanation. Here is a photo of Snow White on the tow truck.

View attachment 603430

I'm glad that was found - it likely saves a lot of unnecessary investigation.

 

[Boydsdodge]

Are you saying you think this is your source of vibration?

 

[ayilar]

Are you saying you think this is your source of vibration?

Quite possible. @cbarge suggested to change those things, and we shall see if the issue is solved. Based on what I saw/heard/felt yesterday, they need fixed in any event.

 

[Boydsdodge]

Quite possible. @cbarge suggested to change those things, and we shall see if the issue is solved. Based on what I saw/heard/felt yesterday, they need fixed in any event.

As I said earlier, disconnect all the belts and run engine. That will show if its a pump, compressor, alt or pulley. Can do one belt at a time to narrow down.

 

[ayilar]

As I said earlier, disconnect all the belts and run engine. That will show if its a pump, compressor, alt or pulley. Can do one belt at a time to narrow down.

Agreed, and thank you for the suggestions.

It was assumed that the belts and fan clutch were not an issue, as the belts looked ok a few days ago (when the balancer was changed) and the clutch had been replaced 3 years ago (and barely used since). Live and learn

 

[furious70]

Having fought a very similar vibration in the previous 383 I had in mine and never solving, I'll be surprised if the AC clutch or compressor bearings cause vibration. Shoulda been really growly and unhappy.
Mine was cyclical worst at 2600-2800rpm.

 

[cbarge]

Are the A/C belts in alignment with the power steering belt?

On snow white the A/C belts run the crank, alternator and compressor.
P.s pumps always ran its own belt separately.

 

[fury fan]

Not to discount other folks diagnoses, but I wish we had done the screwdriver-stethoscope test on that compressor while we were there.
Did the belt squeal happen under heavy throttle or at high RPM?

Related but not:
The TNT I had would squeal those AC/alternator belts at a high-rpm 1-2 shift until I got a *good* set of matched belts.
Had to keep telling the parts-desk guy - gimme a better set of belts, the belt squeal is drownin' out my tire chirp.
So when you get to that point, see if you're getting matched belts.

 

[furious70]

@lemondana used to be able to get us great belts, but I think he's retired.
Mine will squeak a bit when I stab it. All of us should retrofit the 70's top idler pulley on the long span

 

[LocuMob]

On snow white the A/C belts run the crank, alternator and compressor.
P.s pumps always ran its own belt separately.

I was referring to interference due to misalignment.

 

[cbarge]

As I said earlier, disconnect all the belts and run engine. That will show if its a pump, compressor, alt or pulley. Can do one belt at a time to narrow down.

Good thinking!

 

[Ripinator]

Well, quick update here: @cbarge kindly took the car for a one-mile spin with me at the Volo show, and it turns out that the explanation may be quite a bit simpler:

1. the fan was way too noisy, which was the tipoff. @cbarge checked it out, and sure enough the Hayden 2747 heavy duty fan clutch that was installed back in 2020 (less than 200 miles ago) was not spinning freely. So, the fan clutch needs replaced;

2. when driving shotgun with @cbarge, he pointed out that the accessory belts were squealing under his heavy acceleration (he pushed on gas much harder than I had tried when bringing Snow from the alignment shop to the Volo show -- after his debugging Medina 3 years back, I think I see a pattern in his approach ). I also smelled some "burning metal" after he pushed hard (I had not smelled anything when @fury fan and I had driven, much more gently, a few miles to Volo). Turns out that:
a. the A/C compressor seems to have bearings that are on their last leg, and the compressor is not spinning freely -- so it needs replaced or removed;
b. the dual accessory belts, which I had bought back in 2020 and were supposed to be the right ones for the car, look ever so slightly too wide for the pulley's grooves -- the net result is that one of the belts is fraying at the edge, and so I did not drive Snow back from Volo (out of an abundance of caution, and at the recommendation of @cbarge , I had the car flat-bedded back to Wyatt's shop). So, we need to check that the pulleys are correct and that the belts fit exactly.

@71Polara383 can fill in more details, but hopefully this will be the explanation. Here is a photo of Snow White on the tow truck.

View attachment 603430

I'm sorry. . . My standard FCBO offer is now reduced to $2000.