Need Info Regarding Penberthy SV22 Carburetor on 1921 Mercer

I am in the process of restoring a Penberthy Ball & Ball SV22 carburetor for a customer with a '21 Mercer sedan. This particular carburetor has been "messed with" by everyone who should be barred by Federal law from working on such a complex device!

My immediate problem is that the piston in the primitive accelerator pump / power valve system seems to be incorrect, and the "valve" mentioned (but not clearly illustrated) in the 1927 Dykes Carburetor Supplement is missing. While the carburetor will no doubt operate without the needed components (albeit with decreased power) provided that the vacuum source is plugged with lead shot, I consider it to be unprofessional to disable anything if I can instead restore it.

I could really use some photos / dimensions of original parts if anyone has such a carb (perhaps a spare?) and would not mind disassembling it for a bit of picture taking and measurement.

Jeff Dreibus

The Old Carb Doctor

Carbdoc;

I'll try to help. Please find attached a couple pdf files from the parts manual. See if you can figure out which parts you need measured and we can go from there. Does this car (carburetor) have the manually adjustable (from the dash) air valve?

21Raceabout

SV22-1.pdf

SV22-2.pdf

21,

Thanks so much for responding; I had just about given up hope!

My biggest questions are: does the 13818 Pick-Up Plunger fit tightly in its bore, or is approx. 1/32" of side play present? Because that is what the piston has, plus the geometry of the Dxisting pick-up Plunger seems all wrong to allow vacuum to lift it anyway. Also, Dyke's seems to show a "valve" of some sort beneath the piston;

I see no air valve on the carburetor, so I am going to say "no" to an adjustment on the dash. The whole assembly looks exactly the same as the carb in your illustrations, if that helps.

Jeff

Carbdoc -

I'll check the fit and take some photos and measurements this weekend.

21raceabout

Thanks so much, raceabout!

Jeff

Jeff -

Please find attached a dimensional drawing of P/N 13818 Pick-up Plunger. The fit in the carb body is not tight, may be 1/32" loose as you found on the one you are working on. If you have and idea of how I could measure the mating bore of the carb let me know. (Sorry I don't have pin gauges larger than 1/2"). It is a little odd that there is not a spring under the plunger; on the SV-14 carb (used on late 20's Studebakers I am told) there is a spring under the plunger but does not show up in the Mercer parts book for SV-22 nor did I find one in my carb. I may check my other Mercer. Do you have or make the gaskets for the bottom of the float bowl and the second large bolt that traps the plunger? If so, I could use some.

21RaceaboutSV-22 Pick-up Plunger.pdf

Jeff - Let me know if you are having trouble with the pdf, don't seem to be able to load normally... 21Raceabout

Wow, thanks so much, raceabout --- the PDF file downloaded to my computer flawlessly and I just printed it off! I will probably have some questions about the piston once I compare the dimensions to the one which came with the carb I am restoring.

Yes, I do indeed have the fiber washers for the fuel inlet and the cast and cross-drilled "bolt" which retains the plunger; just PM or email me your address and I will send a set to you pronto.

Thanks!

Jeff

jdreibus@yahoo.com

raceabout,

The pistons are nearly identical! They are within .006" of being identical in length, and the balance of the dimensions similarly correspond. The very minor differences in measurement could be accounted for by wear and/or the manufacturing tolerance discrepancies which existed almost a century ago. Apparently somebody thought this system would work "'way back when" . . . though it mystifies me as to how. Oh, and the plunger bore in this carb is .625" in I.D. I measured it with a new piece of 5/8" O.D. brass tubing and it "just fits" without binding.

I forgot to ask: so is there nothing else located in that plunger bore? No valve between the piston and the cast bolt in the bottom of the bore? Nothing located inside of either one?

If not, I'm tending toward the conclusion that the system was designed to operate via some sort of pressure differential that I can't comprehend. From my perspective, for that system to be anything other than a built-in vacuum leak would seem to require defiance of certain laws of physics . . .

And your fiber washers are pulled and awaiting shipment; just get me an address. It's the least I can do to repay all the help you have provided.

Jeff

Jeff -

According to all the handbooks of the day (A.L. Dyke's &c.) I have seen, the pick-up plunger was held in the "up" position by intake vacuum. When the vacuum drops off, the plunger drops and squirts an extra charge into the carb. I have included a couple pages from the 1925 edition of Automobile Engineering (5 vol set) on B&B carbs. I think the picture is bigger/better than Dyke's. Note this seems to be an earlier version than the SV-22 with an air valve on the primary. Also there is nothing (not even a spring) between the plunger and the cast bolt at the bottom.

The Mercer owner's manual says to refer to the manual from the carburetor manufacturer but I have never seen one for the SV-22. Many owners think the best place for an SV-22 is on a shelf in their garage and have replaced with other makes (Stromberg, Winfield &c.) but I am a purist myself.

21Raceaboutsv-22 gas engrng 2.pdf

sv-22 gas engnrg 1.pdf

Thanks once again, raceabout.

I simply don't "get" how that tiny vacuum channel is expected to lift that heavy plunger by a "nail head" which is a fraction of the diameter of the plunger's girth. Moreover, how can the (theoretically) falling plunger be expected to deliver a shot of gasoline as would a conventional accelerator pump when the discharge nozzle's channel is already above the bottom of the plunger when it is pulled all the way up into its bore?!? This fact is what had me largely convinced that this carb has the wrong plunger, but apparently not.

I will more closely study the documents which you sent and try to make some sense out of this.

Jeff

I am also working with a SV-22 on our Series 5 Runabout. I added a very light spring under the "pick up plunger". I have a 1930 edition Dykes

and it looks like there is a spring in the illustration of an SV 29. The spring did not seem to make any difference in the performance.

Also I am still having the same cold start problem with the engine running poorly for several seconds and then shutting off

5 or 6 times before it will run smoothly. Sometimes the shut down is accompanied with a small "lean" back-fire. Any suggestions

would be appreciated. Al Mercer 636.928.8672

Al- For what it's worth I usually need to "flick" the choke to fully closed for just a second or two when cranking it over and then leave it 1/2 closed once it catches until the car warms up.