Looking for Zenith Carb Info

[steamfins]

I’m currently working on my 1915 Mercer 22-70 Touring and I’m looking for any information on a Zenith HN8D Carburetor. It seems to load up and get rich when left at idle for any extended period of time.

 

Much Appreciated.

 

Dan

[carbking]

Dan - checked my records, and found nothing that will really help you, but a wee bit of information.

 

My oldest Zenith service manual is dated 1918. It seems the HN series had just been discontinued, because of idle issues, particularly on the Mercer with the HN8D. A special updraft adapter was designed for Mercer, and the HN8D was replaced with the Zenith L7. The L7 is an updraft carburetor, as opposed to the HN8D being a sidedraft. The L series had a modification to the idle circuit because of the problems with the HN8D.

 

The page in the manual went on to say that some service parts could still be furnished for the HN8D, but no bodies or complete carburetors. It also states the idle modification used on the L7 could NOT be adapted to the HN8D.

 

This manual came from the estate of the chief engineer at Zenith; and as stated earlier, the oldest Zenith service data I have found.

 

Obviously, the idle issue you are experiencing existed a 100 years ago. It may be one of those things you just live with.

 

Best I can do.

 

Jon.

 

 

[Ivan Saxton]

That particular Zenith looks prehistoric compared to the Stromberg OC3 used on 1923-6 Mercer Series Six Rochester-Trego ohv 6 cylinder Mercer.   I made an adapter by a bit of simple lathe work, with the three sections joined by silver brazing.   The 1918 Series 4 ran well with performance and economy, even tough the flange of the carb was smaller than the intake port in the block.  ( I made the nice taper in the adapter).  I also found that the downdraft off a 1942 army Diamond T 6x6 double-boom recovery "wrecker" truck worked equally well.  For that I had to use a fuel pump, because, being a downdraft,  the float bowl was too high for the vacuum tank feed.   The adapter elbow I fabricated was not as elegant, because I made it to invert if I wanted to try a big updraft.   Probably Morris Burrows thought I was a Philistine.   An OC3  would be good if you can find one.  If you can find a bigger Zenith triple diffuser side-draft off something like a Lancia Kappa or the same engine used in the Lancia Pentiota truck of early 1920s, the carb size would better match ,  but you would still have to make an adapter the way I did.  Maybe you could improve the problem if you could add a proportion of something to the fuel to improve the evaporation .  I do not know enough about fuel chemistry to guess.  If you read the section on fuels in Sir Harry Rickardo's text book "The High Speed Internal Combustion Engine", you might find guidance.     The inlet tract on the Mercer Six is same concept as that of the L-head Mercers.

[Guest choknanee]

Six is same concept as that of the L-head Mercers.

[url=https://www.gclub28.com/][color=#f6f5fb]Gclub[/color][/url]

Edited May 15, 2017 by choknanee (see edit history)

[steamfins]

Thanks for the input. I'll probably leave the carb alone for now. Without any documentation I think random adjustments may cause more problems than good.

 

Dan

[Ivan Saxton]

On ‎15‎/‎05‎/‎2017 at 10:15 PM, choknanee said:

Six is same concept as that of the L-head Mercers.

[url=https://www.gclub28.com/][color=#f6f5fb]Gclub[/color][/url]

Mercer 6 and L-head 4 are totally different engines.  The intake tract is similar concept in both, in that the carb bolts onto the side of the engine block, and the intake passage is internal and temperature controlled by the water temperature.   You can alter the meaning of a communication by repeating it with words omitted.

[ak]

Its really fantastic to see the original stuff on a car.  Amazing that it would still be on there given the tedious problems associated with it.  Must be pretty reliable despite its shortcomings to have survived on the machine. 

John