1926 Tudor basically stock except distributor.
I put the original head back on it (getting rid of Z head which made no noticeable difference).
Car ran/performed well, same as Z head performance which made no difference in the original performance as I have said. Performance after re-installation of the original head was good for a couple of hundred miles.
"Suddenly"... the car continues to run ok but their is a significant loss in power. Starts and idles well. The only difference is loss in power.
No head gasket leaks (new head gasket), no oil in water and vice versa.
Check for a broken or weak valve spring and do a compression check. Could be as simple as leakage around the spark plugs.
Ignition timing to far advanced or retarded.
(Message edited by mikerobison on April 24, 2015)
John, you have me puzzled. I wonder how you could not notice any difference when you installed a Z head. When I put my tourer on the dyno we found a 35% increase in power. That was not at all hard to notice on the road.
Maybe something else is going on.
Allan from down under.
The block had been decked and I had to grind out the combustion chambers for piston clearance. Apparently did a poor job. Got Z heads on 2 other T's and there is a noticeable difference but never was on this one.
Unless I slipped a gear timing is ok. It starts, idles and runs fine but just gutless compared to previously.
I cleared the sediment bowl and it needed it but that made little to no difference.
I will do a compression check tomorrow as well as check the plugs for leaking. It is puzzling (to me but then I'm not really a mechanic) since it runs so well with the power exception. Might try a different NH carb to.
I also had a big increase in power/performance with the Z head. A little oil around the base of the spark plugs will show if they leak, but If they leak enough to cause the problem you probably could hear it. Does it burn a lot of oil?
Does not burn oil. Before this it was my most powerful Model T keeping up with my Touring, Z head on a fresh engine done 40 over.
John - The "suddenly" is the part that is hard to understand. If it's not the ignition timing or cam timing "suddenly" jumping out of time, maybe it's not the engine at all,.....maybe the "suddenly" is something suddenly dragging like an emergency brake shoe or a band in the transmission,....???
I saw that Harold.
"Suddenly" isn't precisely accurate. I ran to town (10 miles) and on the return trip home I noticed a loss of power. Took it again today, same issue.
One other thought, maybe something in your spark advance linkage has "suddenly" developed some "slop" and you're not advancing the spark timing as far as you think you are,.....???
Did you re torque the head after it had been run for a while? They need to be torqued about 3 times before everything settles in. Other than that, I don't think the replacement of the head would cause the problem. Does it seem to run roughly, or just less power?
My car suddenly lost power, too. It turned out that the fiber timing gear lost some teeth.
Another easy thing to check for loss of power is the intake manifold for leaks.
If your spark will not advance properly, you would also overheat.
To check for an intake leak, spray WD-40 where the manifold meets the block. If engine RPM increases, there's a leak.
Good tricks all and will hit it later this morning after I go to bed and get some sleep!
I had this problem and it turned out to be one of my coils working itself up and out contact in the box!
Check your point gap in the distributor. That's one of the biggest issue I see when working on cars and tractors with distributors. The gap should be around .018 - .020
Found only 2 small leaks around #2 and 3 plugs.
How hot are your coils?
Some sort of blockage in the intake or exhaust system
Running a distributor but did change out the coil and probably should do the condenser as well.
I suppose it could be a blockage but this car is run pretty regularly as are all my vintage cars. I have no "garage ornaments".
Where I live any thing a mouse rat or chipmunk can crawl into on a car has to be plugged. Lost half my power on my Toyota when a chipmunk loaded the air box up to the filter with food. That cost me a mass air flow sensor. I put a stainless screen over the air box intake. A few weeks later the same car started running on two cylinders the chip monk had moved under the plastic engine cover and chewed up injection wiring. That one cost me a computer. Not a T but the same applies!
My experience with point ignition systems is condenser failures are very common. The symptom is a weak spark and burned points
What lead you to change the coil. Just curious. Did you look at the point condition then?
Something that could account for the poor performance with the z and a further worsening now could be as simple as a restriction in the fuel flow. Surprised no one has mentioned that yet.
You say you have no head gasket leaks, then you later state that you'll do a compression test "tomorrow". Until you've done the compression test, you can't really say for certain that you have no head gasket leaks. Have you now done the compression test?
Not yet. Other stuff got in the way. Even managed to brake a fan shaft on my 1915 which of course put the fan into a fairly new Brassworks radiator.
The fun never ends!
Good fuel flow to carb. All plugs firing at "revved" rpms.
Still need to do compression check but the sun is shining so it is a "yard-work" kind of a day.
Will test for manifold leak before I pull the plugs.
Never found any leaks and threw a new condenser in "just in case". I actually had a feeling a condenser might fix it!
That "feeling" must have been gas...