I am again having a rough running engine on my 25 touring. This has gone on for sometime, sometimes not so bad and other times very bad. I have:
1. put full kit in the carburetor. (Holly NH) Drilled the idle/lowspeed plugs out and found the passages to be clean. (installed allen plugs per Stan's instructions).
2. installed new Champion X plugs (new design) Plugs removed were F11s which acted the same.
3. Inspected timer and found it to be clean.
4. Pulled the head. Valves looked good and springs seemed good. There was a fair amount of carbon which I removed.
I should note that the wiring is new and in good shape. Screwdriver shorting plugs does not seem to indicate any particular cylinder being different. Spark at each plug is strong and consistent.
When the engine is acting up the worst you can smell fuel from the exhaust. Leaning out the carb does not seem to cure the problem in fact through all this it runs best at 1 1/4 turns open.
Is it possible:
1. coils need setting?
2. California alcohol fuel is the offender?
(I should note that after the first encounter with fuel smell I reset the carb float to 5/16" which is 1/16" greater than the book says with no noticeable change)
This is driving me nuts ........ I hope somebody has some ideas. My thanks for any help!!!
A couple of things I would think about:
1. Are you running it on magneto or battery? When you switch between mag and batt is there any change?
2. Any change when you lean or rich the fuel mixture?
definately get your coils set-up by a pro, on an HCCT---sounds like all else is Ok.....paul
This is a bit of a way-out suggestion, but some folks have experienced rough running when the spark advance was in certain positions, because the engine pan bolt beneath the timer was put in with the head down rather than up.
This could easily be a hard thing to spot, because when sitting still and shorting out plugs, the timer is not in the position where that bolt shorts out one coil.
Worth a look-see!
Manifold gaskets may be leaking. although they "look good". you may have some leaky valves such that you have to run it rich to run on some cylinders which floods other cylinders. As a minimum you should do a compression test both wet and dry.
Does anyone know of someone in N.California who has a HCCT? New coils are expensive but........Since I see good consistent spark at each plug I thought coils must be O.K.
I checked the engine pan bolt under the timer. The head is on top and clears.
I have sprayed fuel around the intake manifold with no noticeable change.
My compression gauge won't work properly since the pressure is not sufficient to cycle the tire valve they used as a check valve however removing the tire valve I get an initial reading on all cylinders in the high 40s.
I should have mentioned that battery/mag makes no difference. Adjusting the mixture does effect the running but always seems to run the best at 1 1/4 turns no matter.
Is it possible the problem could be cam bearings or something in that area?
Before you go to the expense of coils maybe there's someone nearby who would let you use a set of known-to-be-good coils for a test. If I were a little closer I'd be happy to do so....
Look into the coils both for amp draw and to check and see if you have a high end coil problem (this is rare and hard to find on a hand spun HCCT. But get it spinning fast enough and you notice missing sparks) Easiest, test if no HCCT, swap coils with known good ones for a test.
Next, all sounds good, but there may be an intake leak. Carefully squirt a blast of carb clean through the straw at the gland while running. RPM change, you have a leak and you can try drawing tighter, I just change gland rings.
So that pretty much leaves mixture, and normally the 1-1/4 is good enough for grenades.
Here's a test you can do to see how close best running is to the old 1-1/4 rule of thumb...
A car will run with a rich mix or a lean mix, yet both have some issues such as overheating, misfire at certain speed, lack power at other speed. Some say to close the needle completely and open it ‘1-1/4’ turns…then do what you have to in order to make it run there. Others say to open ‘1-1/2’ turns for start, then back off a quarter turn to run.
The easiest way to find the sweet spot is to not count stuff at all.
Try what I call the 6's test. While running deliberately a little rich, pull the spark advanced to the 6th click, the Throttle to the 6th. Then slowly rotate the mixture by 1/8 turn clockwise, pause for 6 seconds and listen and feel for a change.
Do again until you discovered a sputter. Go counter clockwise 1/8 turn and then go for a ride, go from low to high and if you have a fuel sputter when high is caling for catch up, reach over and open the needle valve another 1/8 turn counter clockwise. Do the low to high gear, idle to 1000 rpm again. No sputter then this is the real sweet spot for the future. Mark 12 o’clock high if a knob when done. If bent wire type, mark the angle somewhere.
This mixture setting will be good and optimized for what you run.
The remaining issue might be starting a cold engine. When cold, richer fuel makes it easier to start. Should your car with the above setting run well yet be a mule to start when cold, simply open the needle valve ¼ turn CCW, do a few choke pulls with ignition off, and fire it up. Before driving away ¼ turn CW to put it back at the sweet spot and good to go.
You may wind up at the 1-1/4 turn point, you may not, but now you know you have the best balance for what your engine wants and your carbeuration is correct.
If you contact Ron Patterson he will loan you a good set of coils to try. Click on the part supplier tab on the main page of this web site.
I want to thank all of you who have suggested solutions. I'm going to go to a 4th of July celebration in a town about 25 miles away with the Model A club (there is no T club here). They tell me that there is an old fellow there who is a Model T expert. If he doesn't discover the problem I intend to try to contact Ron Patterson as to sending the coils to him for check out. Again thanks everyone!!
John;;; Try starting it in your garage at nite and turn out the lites and have some one move the throttle back and forth to speed up and slow down. In the dark check the coil box for signs of spark traces on the wood.
If ANY get John Regan's plastic coil box kit.
John, do like Henry said and borrow someone else's coils. I had a miss that drove me crazy. I did everything you did and more, including the plastic coil box kit. I had tested my coils twice on a HCCT, and someone else tested them again on their HCCT. They seemed to be OK. At one of our club workshops, I checked them on a Strobe-o-spark. They were sparking OK but the capacitor test showed that they were weak, but they were actually no worse than a set out of someone else's car that ran good. Finally I took his coils for a spin in my car -problem solved! My car ran great! I started putting my coils back in one by one, and there was one coil that ran bad every time I put it in even though it showed the same as 7 other coils when tested.
What gap are your spark plugs at? You might try a different gap, some people recommend .025", others prefer .032".