Although our backup IMP52 regulator was still working fine, I was not impressed with it's internal design. I talked with Nash Fuels and Century Fuel Products, both good Impco distributors. They are both good outfits but have no real technical support by Impco, which is now owned by a bigger alternative fuels company. I think they both could provide very good basic support for more typical applications. I state this as a warning to others- there seems to be no such thing as tech support from Impco anymore, not even to their higher volume dealers. The brilliant guys who designed IMPCO's products and knew how to apply/modify them for new applications are long gone.
I studied the Impco regulator catalog, looking closely at the internal parts in the exploded view, and found that only the Impco/Garretson KN regulator seemed suited to our gulping intake Lister clone and 10" of WP gas supply. They fortunately are fairly cheap, on ebay for about $50, so we ordered one to try.
The KN regulator has a large 6"" silicone diaphram that operates a 2.5" long glass filled nylon teeter-totter against a spring (adjustable tension). The tetter-totter opens a silicone face disk against the about 0.5"", 10" WP brass gas inlet. A very simple design. We have the 3/8 NPT outlet (wish it were larger) immediately bushed up in size to feed a 3/4" hose about 24 inches long to the carburetor. In the past with the IMP52 we've found that this hose size was required with any length over a few inches.
It started right up but lacked power initially. With a minor adjustment to allow the internal valve to open an additional 1/16", and the carburetor adjusted richer, we seem to have a nicely working engine, again. I'm convinced that the internal mechanisms should hold up much better to our pulsing intake than the IMP52 regulator, where an 1x1"" aluminum cone on a shaft is lifted by diaphram. The IMP52's 1/16" cone shaft was unbushed and in time it bound were it went through the die cast aluminum body. We were also pleased that now both idle adjustment screw and carburetor rich/lean adjustments worked as they should, and with the IMP52 they made no difference at all. This makes me pleased that we are finally "in the zone" for the CA110.
The īntake "gulping" of the DES 8/1 propane conversion seems to be THE big issue for a propane carb/regulator. The CA110 was specifically noted as suited for this, with it's large diaphram directly lifting a metering cone (no shaft). It seems the KN style regulator is a better match for it in this application.
I'll report back as it logs more hours of service.