Bonjour,

Wanted to share with you the solutions of a multi-layer issue I had related to engine vibration. Might be that some of you have a similar issue.

When I bought my Pantera 5 years ago I noticed quite some engine vibrations while driving the car. The vibrations were present during the entire engine rev range with a significant peak at 2400 rpm. The vibration level was okay for a short drive but for longer travel it became annoying.

  • I started changing the damper on the crankshaft since the rubber elements of the old were already quite brittle. Unfortunately this had no influence on the vibration issue.
  • Due to a burnt head gasket I had to overhaul the engine and used the opportunity to get the crank balanced. The previous owner installed a stroker kit in the 80th (from 351 to 371). The machine shop found 80 grams of imbalance. After re installation of the crank I noticed a very significant reduction of vibration for engine rev above 2700 rpm, but I had still the 2400 rpm peak and vibrations at low rpm.
  • By chance I found that both engine headers were in contact with the body structure at two very small areas. I fixed that issue and the 2400 rpm peak entirely disappeared (!) but I had still some light vibrations at lower rpm.
  • Again by chance Mike Drew told me about engine mounts that have been sold in the past by a California supplier for Pantera parts which were stiffer than the original one. I checked and found those installed on my Pantera (see photo; original (right side)). I changed the engine mounts and also got rid of the light vibrations.

It was a longer journey to fix the vibration issue but I’m very satisfied with the result. Hope that this small report might be useful for some of you.

Greetings from South of France

Hartwig  

Engine mounts

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Original Post

 I have no doubt that the vendor insulators may have differed from the original insulators with a stiffness that would more firmly transmit vibrations.  But I wonder if another aspect of the vendor insulators also failed to dampen vibrations like the originals.  

Looking at the original and replacement engine mount insulators the only major visual difference is the circumferential groove molded into the originals.

 I am far from an engineer but couldn’t  that groove allow the insulator to flex and thus deflect some energy (vibration), in a manner similar to a spring flexing?  

🧐❓❓

Larry

I believe the aftermarket insulators are made from black polyurethane. They compress over time, due to heat from the exhaust, enough for the headers to contact the frame. Notice the difference in thickness vs. the OEM insulators on the right. Jack "Bosswrench" DeRyke has been advising people to avoid these aftermarket insulators for at least a couple of decades!   

True, poly motor mounts are a problem besides being stiffer and taking a set. Most serious is the fact that if the car is used hard (such as simply driving on the autobahn, or track events, poly motor mounts will MELT from header heat! This is particularly bad on the left side, as molten poly will run down and cover the joint between the upper and lower aluminum mounts.

On the right side, the entire mount assembly can be removed as one piece, but on the left, the gearshift rod goes thru a recess between the upper & lower mounts. So the two halves MUST be separated to remove them from the car. Unless you have a big hunting knife or preferably a chisel and hammer at hand, the left mount cannot otherwise be removed. Here, poly was NOT an upgrade except for gently driven show cars.

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