Right equals Rich?
Left equals lean?
Is that accurate?
Clockwise looking at the top of it leans the mixture. Counterclockwise makes it rich.
CCW equals fat, CW equals lean
Oh, ok. I've had to clean soot off my spark plugs about every hundred miles or so. Is that normal?
They did not foul out but I could feel one cylinder getting weaker.
I looked inside the cylinders and saw quite a bit of carbon buildup. Carb is a recent rebuild NH
Ok, so it is literally a fuel flow valve like a spigot.
Got it now. Thx!
Yeah, a spigot that adjusts the air/fuel mixture. Well maybe not like a spigot. More like a spray needle valve. To set it turn it in (clockwise) until it stops. Then turn it out 7/8 to one turn (counterclockwise). Then start the engine and run it meanwhile lightly adjusting the spray needle valve in and out lightly until you find the spot where the motor evens out and runs the best. Then, leave it alone. Don't touch it again unless you have reason to believe the motor might run a little smoother by "tweaking it a little. It is not a spigot, it's not a valve to be used to open or shutoff the fuel. It's called a spray needle valve and it adjusts the fuel/air mixture in the carburetor to its optimum running mix.
Yes, I should not have implied that it can be used as a shut off valve.
It is adjusted within a quarter turn right now at current temperature, etc.
I'm trying to diagnose the sooty spark plugs and want to aim toward the leaner side to see if that helps without increasing operating temperature.
Chris - A good method for obtaining optimum fuel/air mixture is as follows:
Driving along at comfortable cruising speed and with engine running at normal operating temperature (in other words, fully warmed up engine) slowly close mixture valve (clockwise) until engine begins to run a bit rough, note position of mixture valve knob, then slowly open valve until engine smooths out again, and continue slowly opening valve until engine again begins to run a bit rough again, and again, note position of knob and then adjust valve to approx. midway between too lean and too rich. Normally, rotating the valve knob from too lean to too rich will be somewhere between a half or three quarters of a turn of knob. Usually, once you have obtained this adjustment, you probably won't have to touch it again. If you find that the engine starts better when cold by opening mixture adjustment approx a quarter turn toward "rich", it's okay to do that, and as soon as engine warms up a bit (only takes a minute at most) don't forget to turn the mixture adjustment back to the normal running position that you have "memorized" by noting position of the little mark on the knob.
Additionally, after you have established the "ideal" running adjustment, then (and ONLY then) you can take note of the amount and color of spark plug soot. It should not look wet or black and oily, but dry and just sort of "tarnish" or light "brownish" color. Light coating of soot is normal. Hope this helps, and as is often said, "YMMV" (your mileage may vary),......harold
Mike Garrison - My apologies sir! I totally missed the fact that you had already explained proper carburetor adjustment! As the kids would say,......duhhh......!
Oh well, reading the same basic "explanation" from two old guys like us should be convincing, huh? .....harold (:^)
Harold, you did such an excellent job with your explanation.
Thanks Mike, except that thanks to "auto-correct", I called the normal spark plug soot color TANNISH, and not tarnish! Oh well, I guess in reality, "tannish" is not really a word!
Harold and Michael,
Thank You very much! I was adjusting by ear at idle and my hearing is not very good.
I spent a lot of time in the sun yesterday and my skin appears to have taken on a "tannish" appearance.
Michael, you're lucky. For me barely 20 minutes in the sun and I look like a lobster! Dang B.P. medicine anyway. Says "stay out of sunlight"....yeah, RIGHT....like that's possible the way I like to play with the cars! SPF 50 by the gallon.
IF I may Chris.
View from the Left side. Wore out '19 engine in a (mostly-sorta) '24 roadster pickup. Speaking of acronyms, NSFT Not Suitable For Touring.
Spigot, you ask? Yes! IF like a garden hose "Spigot". :-)
You have an NH? For my Little Ford AFTER starting and warming just a trifle... I open it up a half turn plus for starting depending on the temp.
Adjusted just so for idling around and a quarter turn "IN" if I'm getting into it with the speed/throttle.
Don't touch the carb after starting? Sorry Michael, NO WAY! Listen to that engine and adjust constantly to IT-self. Set nice for idle means too damn rich for speeding.
AND we have to reach for it.... Ugh. :-)
IF I understand correctly, some of the nicer carbs allow you to "set it and forget it". NOT an NH in this man's book. Never.
I am constantly adjusting/reaching.
For me, I need to to figure out a small u-joint for my carb adjust, so it goes thru the choke hole in the dash so I can adjust easier.
For me, choking is done at the radiator. NOT inside the car...
An engine (no matter what kind/style) should run the very best we can allow it to.
Adjust that carb as you go.
Duey C - First sentence in your post says,...."Wore out '19 engine in a (mostly-sorta') '24 roadster pickup."
Now then,....in looking at your profile photo of your '24 roadster pickup and noting the Personal Quote on your Profile which states: Minnesota's Crappiest Model T Ford",.......
Is it possible that "Minnesota's Crappiest Model T Ford takes a bit more "constant adjusting" of the carburetor to keep it running at it's best?
Ha, ha,....just give'n ya' "the business" Duey!
But honestly Duey, my '27 depot hack runs just great and NEVER requires any further adjusting after I start it from cold. In really chilly weather, I might turn the knob a quarter turn richer to start, but after a minute at most, I turn it back that quarter turn to it's normal running position, and NEVER have to touch it again! And I have "experimented" while driving under different conditions (like a long uphill climb for instance) and changing the carburetor adjustment from it's normal running position does absolutely NOTHING to improve the power or smoothness of how it's running. Totally stock '27 "T" engine with totally stock Holley NH carburetor,....carburetor and engine rebuilt by Steve Tomaso of Steve's "T" Works about two years ago! Honest to goodness,.....I wouldn't lie to ya',.....harold
Thx Duey & Harold!
Fuel injection systems have oxygen sensors to tell them to slightly adjust the mixture. WE are the O2 sensors for our Model Ts! Every day the weather varies in theses foothills of Tennessee.
I'm thankful that mine only needs a slight 1/8 turn at a time and this thread was just to verify the direction that's leaner so I can reduce the soot accumulation on the spark plugs.
Duey, I think I see the problem here. In your profile you list your occupation as "wrencher and thinker"! Well geez, your problem is obvious. Everybody knows that the normal Minnesotan brain hibernates a minimum of 6 months out of each year or you'll wear it out. You are, without a doubt, over-taxing and expecting too much from your equipment.
Okay, I'll stop. I saw Harold put in his little dig on ya and I figured I better jump in on it too.
But seriously, with any one of my three Model T's I seldom if ever adjust my spray needle valve. I've tried to optimize the way the engine is running by trying to improve it through some minor mixture adjustments but it seems that "sweet spot" always results in the air/fuel mixture being set in the same place.
Along those same lines, once I start the car and it's had a chance to warm up, I set the spark advance to the same setting that seems correct to which ever setting gives me optimum performance and results in the engine running as good as it can, then pretty much leave it alone. When I shut the car down I pull the spark advance lever up all the way so I minimize having the engine kick back against the starter the next time I'm going to fire it up.
Now for my disclaimer; I've only been doing this model T thing for a few years. I've been a borderline shade tree mechanic for 60 years but I think we all agree the Model T Ford is a different kind of cat. Every time I get to where I think I've got it figured out it changes the rules and a whole new "thinking" process has to start. And seeing as how the Minnesota brain is idle six months out of the year, well...
I got off the NH band wagon a long time ago because I also found that they need more attention then others. (I had an open mind on em because they seemed to be what all the ice cream set was using LOL) I have run them on several occasions on my car which is good shape motor wise. The couple I tried were good clean carbs with tight throttle shafts. I am going to stick with Kingston L4, Schebler, Marvel or Stromberg.
Back to the question...oh it's been answered.
It's OK, G. That game changing, mind-of-its-own thing will keep even the full time thinker
scratching his grape. On the TT, I have rebuilt the coils, coilbox, wiring harness, timer, and
pretty much everything relating to making it go down the road in a reliable manner. The carb
was left "as found" on account of advice from my "race team" that said it was OK. The L-4
Kingston was said to be sluggish, but reliable, so it was left to do its thing, including non-stop
adjustment of the air-to-fuel mixture upon every rise or fall of the road grade. The truck shook
and rattled and I was told this was pretty much what a TT is going to do on its best days, so
I just ambled down the road and didn't give it much more thought.
Well, last week, the thing began sputtering and I was barely able to limp it in to The Ranch
(where the evening plan was to beat a dent out of my replacement oil pan and get it on the
straightening jig. Instead, the whole gang jumped in to help iron out the problem. At first, it
was thought I had broken a second valve in as many weeks, but a compression test revealed
a 60-60-60-58 reading. so then a weak or stuck spring was suspected, but that was ruled out
after opening the side galley and playing with the valves there. Coils were checked and deemed
good, so attention turned to the old Kingston.
Off it came, and a gutting was performed. Parts were cleaned and/or replaced and it all went
back together again with a heavy crimp on the air/fuel mixture fitting that was always self-adjusting
to richer. Back on the truck, it still ran like doo-doo, so off it came, and an off-the-shelf NH was
produced and installed. The truck has never run so smooth.
But with that smooth running came a whole host of other problems. The idle no longer hits bottom
when the control arm is fully raised. Idle itself is a hard thing to find. Like when I want combat
park the old dog in the barn without punching it through the back wall, a smooth and steady idle
is good to have ....
.... so, while removing the "think" part of one end of the operations, I have discovered a whole
new cluster of things to be thinking about as I mosey. It seems these thing DO have a mind of
their own to some degree, and I remind myself that this was the first step away from horses,
another drayage conveyance that had even more of a mind of its own !
I need a nap. :-) Or a brain rebuild. ;-)
I'll take those digs (as I usually deserve them) and will remain slightly envious of those that don't have to play with their carbs much. :-)
Heck, it's part of my T's charm. I think I'll take it for a spin now.
Duey - All kidding aside, this really is an interesting thing! Honestly, you can trust Mike and I,.....for some reason, it seems that our NH Holley carburetors each seem to be carburetors that do not require continual adjusting. In years of reading this forum, I do not question one bit, the fact that identical carburetors will (and do) act differently. I can only think that over 80+ years of use, wear, deterioration, etc, etc, they must begin to develop some "individuality" which causes them to be something less than "physically identical" as their running characteristics become something less than identical. Perhaps there ARE visible differences in physical characteristics that would account for actual performance or running characteristics that would account for why one requires continual adjusting, while another does not. Even I can think of a few possibilities, such as throttle shaft wear and/or wear in the iron carb casting caused from years of throttle shaft movement which causes vacuum leaks, a plugged (or partially plugged) passage like the one under the brass "HOLLEY NH" name tag, maybe differences in the shape or angle of the tapered "working end" of the needle valve, or misalignment of the needle with it's seat! As Unca' Stan would say,...."I dunno"! And speaking of Stan Howe, there's nobody that understands carburetors better, and maybe Stan could chime in here and explain why HOLLEY NH's seem to display such running performance differences,.......??? Stan,.......are you out there? Maybe on one of your "coffee & cookie breaks" from the shop, you could tell us what you think,.....it IS interesting,.......harold