I am still chasing the source of my rough running
Vibration issue. Took up the rods is quieter but still rough I am going to do a valve job and remove the zone head I put on and see if that helps. Philip
The Z head is most likely not your problem. Do a compression test first, before removing the head and possibly doing an unneeded valve job.
Do you use the coils & timer yet? If so, what is the condition of your timer? Have your coils been rebuilt? How old are the plugs?
The first order of check would be fuel mixture. Try to find the sweet spot between too lean and too rich.
Next check for spark at each cylinder. Take a screwdriver with insulated handle and short between the conductor and the head each spark plug, one at a time. If shorting one or more plugs results in no slowing of the engine, hold the screw driver in the same position but move it about 1/16 inch from the plug wire. Look for a spark to jump. If a spark jumps, you either have a bad spark plug, very low compression, or lack of fuel supply to that cylinder. If no spark, look for a bad coil or problem with the timer or wiring between the timer and coil, this would include a problem with the coil box. If running on a distributor, check points, condenser, rotor and cap. The cap sometimes has a carbon track causing the spark to ground internally.
Check compression on all cylinders. at low elevations you should have high compression and about equal on all cylinders. somewhere around 70 psi or higher with a Z head. If one or more is low, you could have a burnt or stuck valve. If you squirt a little oil in the low cylinder and it raises the compression, you could have worn rings
If you have very low compression on two adjacent cylinders you could have a blown head gasket. It is very small space between 1 & 2 and between 3 & 4. The higher compression of the Z head could also make it more likely to blow a gasket. If you take off the head, take a very straight edge such as a framing square and check that the surface of the head is completely flat. If it is warped you might need to resurface the head.
Be sure to check for the more simple things first before taking anything apart.
when i had the head off i saw that the car has the
factory style valves the clearance on some of them is a little tight at about .012 would the stock cast iron head valve need more or is that good? philip
The valve stem to lifter clearance has nothing to do with valve lift or which head you have on. The clearance is there for expansion. You could open the exhaust up to .014.
Have you checked for vacuum leaks?
Which ignition system are you running?
If coils,have they been checked?
"I am still chasing the source of my rough running"
At what engine speed is it running rough?
Does the roughness smooth out as engine speed increases?
Have you checked fuel flow?
If you have posted this info before you might add a link (cut and paste the address to this one) to this one. Might help, not everyone will have read anything you may have posted before.
i have 4 1950s vintage kw coils that look like they have been rebuilt. no i have not checked them the
club i just joined has a tester i will try to get
the carb is a nh side drain
i have good fuel flow
the car starts and idles good as soon as rpms are increased it starts to vibrate when driving it
there does not seem to be a spot where it just motors along so you end up speeding up slowing down trying to get the rpms where the car does not vibrate
it is hard to put exactly what it does into words
i have driven a friends car and there is something wrong with mine.
Phillip- the club you have joined- maybe one of the members will bring over a set of “known good working coils” and help you diagnose the problem. That system works and you meet some good new Model T friends too.
Norman - why would low compression keep the plug from firing? It might keep the cylinder from making power, but I can't see why low or zero compression would have any effect on the plug sparking. The same question applies to lack of a fuel supply.
yes the club i am in is a great resource. we looked at the car together weather did not permit a test drive. i was advised to take up the rod bearings
and i have. the first club tour is next weekend
100 mile round trip do not think i will try it with the car running strange.
Rod bearings would make a knock, not run rough.
If the vibration is showing itself when the car is underway;
Has the rear end been checked?
Are the tires out of round?
Are you running battery or magneto for coils?
Do you understand how to use the spark lever?
Would I drive on a 100 mile tour, maybe if there is a trouble trailer going on the tour. But to me sounds like there are some bugs to work out first. I think you might have a different person look at the car. From what I am reading, there is more then loose rods involved.
How is the front end? Is the clutch slipping at speed?
Low compression would not keep the plug from firing and lack of fuel supply would also not keep the plug from firing. The first thing to do is see if all plugs are firing. Next check fuel supply and compression. Any of these things could make the engine run rough.
Since the car idles smoothly, the problem is probably not the plugs firing. However, if the car misses during a hard pull, a weak spark could cause the fuel in that cylinder not to burn and that would cause misfiring under power. If you could borrow a set of known good coils. Place them in your coil box and see if the car runs better with them. If so, you have one or more coils with a problem. Substitute your coils back into the box one at a time and see if the problem comes back. That would isolate to one or more of your coils.
If the car begins to sputter like it is running out of gas, but runs better when you back off the gas, you might have a partially blocked fuel supply. The carburetor bowl would fill at idle and at low speeds, but when you open the throttle, your fuel in the bowl would drop.
A vacuum leak is more noticeable at idle, so that is not likely your problem. Compression is not likely the problem either because of the smooth idle.
The two things most likely to be the cause of your problem would be weak spark and the other partially plugged fuel supply.
i will double check the fuel supply i dont think it is in the drive train i get the same vibration sitting still at say half throttle. i suspect some sort of misfire it acts as if it is horribly out of balance but the mag works so there should be no missing magnets. that is why i was going to do a valve job and set the gaps a little wider to make sure the valves are closing fully on all cylinders.
when I first got my 1927 Model T, it came with a recently rebuilt J. C. Whitney engine installed.
It was hard to start and would not run on Mag.
It had little power and always ran rough.
I did 3 valve jobs with no improvements.
Then I installed another rebuilt engine, with the same results.
The only things not replaced were the coils and the Vaporizer carburetor.
They were all bad!
There are a couple things not mentioned in all the good suggestions.
If a re ground cam the valve timing could be off. Check to see if all the intake valves close at the same piston height and all the exhaust valves open at the same piston height. This can be fixed by adjusting the valve clearance. This can cause the engine to run "rough." If this is the case then search for instructions on how to set the valve gap by the timing method.
If it is running evenly but seems like it is out of balance, then maybe it is. The flywheel with magnets and the clutch drums can be very out of balance. The only cure there is taking the transmission apart and balancing everything.
Follow the excellent instructions by others first.
Real silly question Philip. How quiet is your muffler? Can you hear whether it's running on all four or no at half throttle?
I'm a bit deaf and have straight pipes on two of mine plus I modded the muffler on the good one so I can hear the beats/beast.
That's why I ask. :-)
Interested to know your results.
It has a muffler I can't really hear the exhaust note while driving it is a touring car. I checked compression with the z head I have 60 psi on number one and 70 on 2 3 4.
Since it is a vibration and NOT an outright miss I am thinking you might be running an ANDERSON timer which is a "slap" type timer with contacts that can get out of adjustment and make the inter cylinder timing way off. Oddly enough they don't missfire but just can get so far off that you may get inaccurate and uneven firing even when running on magneto. Had a friend at a tour last summer and he was having the same issue. We put the car on BATTERY and pulled the hand crank very very slow until we heard a coil buzz then looked at the front engine pulley pin position each time a cylinder fired. It is a simple parking lot check up of the timer. We found his Anderson timer was way off although the engine did run. The firing position of each cylinder should result in the pulley pin being exactly at the same place for 4 times in a row. Every 180 degrees of rotation a cylinder fires and you can pull the hand crank very slow and stop when you hear the spark of a coil begin then note the position of the front engine pulley pin. It SHOULD be in exactly the same place every time regardless of which cylinder is firing. His varied more than 30 degrees at times. He swapped the timer for a new one and it ran like a swiss watch. I remind you it was NOT missfiring altogether and it was better when running on magneto but not by much. Coils ran fine but we knew those were new and not the issue since they had been swapped into another car and ran perfectly.
thank you john i will look at i am running the anderson. i need to get this thing right it has been driving me crazy. philip
well i took the z head off and replaced it with the ford head and solved my vibration issues it seems
that the z head was too much strain on the motor.
i will hang it on a nail until i rebuild the engine.
now its time for some driving. philip