rebuilt 301 vibrates at around 3k RPM or 40 mph

Rusty Muffler

Rusty Muffler

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Getting down to the nitty gritty, I can feel the engine strobing. It has about 500 miles on it and there's probably nothing I'm going to do about it, but what do you think it is? I figure it might be something out of balance in the torque converter? It had been sitting 9 years so maybe crud settled in one part of it? None of the cooling fins were broken.
 
Nothing in the power steering pump to get out of balance. If you feel it in the steering wheel, and the front tires are balanced, it could be a front u-joint. The tell-tale is that it comes and goes. I'm suspecting the u-joint.

CBODY67
 
CBODY67 said:
Nothing in the power steering pump to get out of balance. If you feel it in the steering wheel, and the front tires are balanced, it could be a front u-joint. The tell-tale is that it comes and goes. I'm suspecting the u-joint.

CBODY67
Click to expand...
You may be right about that. I've heard an odd random sound like a bird chirping that could be a dry U joint but I could swear I greased them. I'm at an age where I'm constantly second guessing myself :(
 
Rusty Muffler said:
I'm at an age where I'm constantly second guessing myself :(
Click to expand...
This can be one of the first signs of "low hormones", by observation. Been there, done that.

"Second guessing" can be good, to remember there are always options that could be employed.

"Chirps" when first starting off from a stop can also be a sign of "No Grease".

Enjoy!
CBODY67
 
At the risk of making this easier to figure out.... And sometimes I think we can't have that...

Does the engine vibrate at ~3000RPM in neutral, with the car sitting still?

How about driving at 40MPH, does the vibration change when you put the car in neutral?
 
Big_John said:
At the risk of making this easier to figure out.... And sometimes I think we can't have that...

Does the engine vibrate at ~3000RPM in neutral, with the car sitting still?

How about driving at 40MPH, does the vibration change when you put the car in neutral?
Click to expand...
It seems to stop vibrating when in neutral. Since it's "break in" I need to adjust the valves and make a compression check later this week.
 
I don't think the valves would cause any vibrations. Maybe some clicking noise, but that should be all. Aside from the ball and trunnion and the rear universal joint, maybe the drive shaft has a slight bend or is out of balance.
 
57fury440 said:
I don't think the valves would cause any vibrations. Maybe some clicking noise, but that should be all. Aside from the ball and trunnion and the rear universal joint, maybe the drive shaft has a slight bend or is out of balance.
Click to expand...
As far as the valves, they seem a little too quiet whether they are this problem or not and should be rechecked. I'll be rechecking the u joints for grease although if they are causing this then they probably should be replaced too. I'm going to have to look up ball and trunnion. Is that just forward of the "drum" emergency brake?
 
Since you have to get under there to have a look and feel, spin the driveshaft and see if any welded on weights might be missing or if a weld came loose.. a lot of time has passed and who knows what might have been done in the past.
 
Finsinthemirror said:
Since you have to get under there to have a look and feel, spin the driveshaft and see if any welded on weights might be missing or if a weld came loose.. a lot of time has passed and who knows what might have been done in the past.
Click to expand...
I've determined it's the engine at around 3k rpm when car isn't moving. I can feel it misfiriing at about that rpm and creates a repetitive vibration. Could carburation cause this or the distributor? It's at cruise and not hard acceleration.
 
Presuming you have the point dwell set at the correct value and point gap in similar, what does the dwell look like the rpm the roughness starts? If you unplug (capping the vac line unplugged) the vac advance, how might that affect it?

Might need to seek out an older repair shop which might have one of the ignition oscilloscope items to watch what the spark plug firing/ignition system is doing. That would quickly identify which cylinders are having issues or if all of them are contributing. As to what the ignition system is doing.

Just some thoughts,
CBODY67
 
I had a 1974 318 that I put in a 57 Plymouth years ago. The engine had been sitting for a long time. I put a rebuilt carb. on it, new plugs, ign. wires, cap and rotor. It had electronic ignition. Everything was good and it started right up and idled perfectly. It had a 904 behind it that also worked good. It had the same problem you are having. When I first got the engine, I drained the oil and filter, and it was pretty bad. After about 200 miles I changed it again. The problem was still there. You could drive the car, but it was annoying. After about another 200 miles, the vibration went away completely. I was never sure what happened, but maybe one or more of the rings were hung up.
 
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