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Has anyone adopted modetn a/c to a 356 engine? I tried a search but didn't find to much.

Is there such a thing as a double groove crank pulley for such an application?

I have installed a passable adaptation of a modern system to a 356 on my 47 Clipper. I tried to keep the old prewar look while adding a couple of modern touches. Mine is custom made using modern components with a repro case and rear vent and an added front vent. Installing a regular unmodified underdash or trunk unit would be the same as far as making it work.

One of the larger issues you will have is voltage. No one makes any components for 6v AC anymore. Options are 1) convert the car to 12v, or 2) in a basic NON ELECTRONIC controlled unit change the blower motor to a smaller 6v heater type (or run the 12v motor at a reduced speed), and 3) use a hybrid 6/12v setup. Sanden clutches need a minimum of 7.3 v to pull in so if the generator is putting out a high enough charge voltage (7+v), the clutch may be able to work leaving the car at 6v. Several have managed it. On mine, because of other requirements for the custom build I chose a basic unit but elected to do the split voltage.

I don't believe there are any extra groove crank pulleys available for the 356. Packard drove their prewar compressors off the fan pulley and postwars with AC had a different engine and vibration damper. Those dampers had narrow grooves with the vibration portion behind the grooves. The AC or PS extra crank pulleys bolted on to the front of damper. To do something with the 356 crank pulley would require some adaption and fabrication. With the large damper portion in front of the wide groove, even if a pulley could be mounted I am not sure there is room for that much extra width on the crank pulley.

There was a fellow who reproduced the extra groove fan pulleys and another did the prewar compressor mount. The gentleman that did the mount has passed on and I do not remember the name of the person who did the pulleys or know if he or any of the pulleys are still around. I bought one some 20+ years ago and don't recall seeing any information on them since that time.

Here is a photo of the fan pulley. One downside to the original size AC groove is the old belt width is not easily found today. What I was able to find in a modern belt was unavailable in a short enough length to do a decent layout and keep the compressor a bit closer in. Another issue is the available wide groove width for compressor pulleys are limited. 3/4 is the largest easily found and the original groove and belt is slightly over 7/8. I wound up using a compressor pulley for a semi truck or maybe heavy equipment AC. Between the belt width and groove sizes, my implementation is not perfect but workable.

Perhaps a machinist could make a new fan pulley and choose a narrow AC groove width more suited to the belts and compressors now available. Depending on what is done there, that would determine if or how much the fan has to move out to clear the AC belt. On the stock width I made an adapter to space it out approx 3/8 inch.

As to the compressor mount, Ross has made a simple implementation for the Sanden compressor as used on later inline 8s that would work well on the 356. The issue is it mounts the compressor closer in so would need a shorter belt than is available on the large D width belts used with the original pulley. The smaller groove fan pulley would be a must.

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