Engine mounts

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Bill Lyons asked about what I used for engine mounts in the thread below about getting my engine back in.

I used standard isolators available from McMaster-Carr.

When I first got the car in 1991 and thought I would dig into its restoration right away I bought some isolators from a vendor that were supposedly correct replacements for the original Pierce doughnuts. They were rock hard 80 durometer rubber that looked correct, but after I pulled the engine I found the isolators on my engine were much softer 40 durometer. My vague recollection is that I found the isolators being supplied by the vendor were used for a Caterpillar diesel. Since my engine had been removed once in the 1960’s it is entirely possible that previous owner used isolators that were too soft, but I doubt it.

It is clear form the McMaster Carr catalog that the isolators used by Pierce were a standard item that is still produced today and available in hardness of 40, 50, 60, 70, and 80 durometer. The load capability goes up with durometer, with the static load capability of the 40 durometer being 250 lbs each. With 8 doughnuts that makes a total static weight capacity of 2000 lbs which corresponds the closest to the assembled weight of a Pierce engine/clutch/transmission/freewheel/power brake.

They are $8 each and drop right in. They differ from the originals in having a complete steel cup underneath instead of just an outer support ring which is pretty much un-noticeable appearance wise if you paint them black. For something like this I am definitely a function over form guy, I want the correct isolator compliance.

The McMaster-Carr part for the upper big doughnut:

2.75″ OD, .63″ ID, 40A, part #64865K81

The smaller lower doughnut that fits on the underside:

1.75″ OD, .63″ ID, 40A, part #64865K85

I am reusing original bolts and tube spacers that will set the nut location preventing the doughnuts from being crushed from over tightening.

Jim

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Great information.

Thanks for sharing all the details!

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