Y-Block perpetual misfire

[Daves55Sedan]

This is on my '55 Ford sedan with 292 V8/2bbl loadomatic dizzy and Ford EBU carb.
First of all I went back and re-read all of runmikeyruns misfire post that went from July 2018 thru Oct 2018.
It ended up that one of his valves was stuck, but he got it loose with PB blaster and he replaced the rubber umbrella valve stem seal.
On that note, it has been my experience that when a valve sticks in the head, the rocker arm pushrod will fall out of the ball-stud on the rocker arm when the camshaft lobe turns to the low point. That is the easiest visual tell-tale sign of a stuck valve, but I didn't notice he ever mentioned that.
Anyway, here what happened to my 292:
I was going down the road, pretty as you please 35mph, when all the sudden the engine started running real bad, like maybe 2 or 3 cylinders quit firing. Luckily, I was not far from home and I coaxed it back to my garage. It would not stay running without some throttle, so I had to keep the engine revved to keep it running on the way back.
First thing I did was replace the points and condenser with new ones. I started it up and there was no difference.
I popped the valve covers off and looked at all the push rods to see if any had fallen out of the rocker arm ball studs. Nope!
I put new gaskets on the valve covers and put em back on.
I took the distributor cap off and noticed the underside of the towers were slightly worn by the rotor tip so I replaced both the cap and rotor with new ones. While I had the cap off, I jerked on the dizzy shaft and there is no free play. The cap hold down spring-steel clips hold the cap down tight too, so no problem there. It does also have the little spring-steel clip on the end of the shaft that the rotor fits over. I cranked the engine to TDC and looked at the dizzy. The timing appears right on the money, so that rules out any slippage of the timing chain.
I start the engine again, no change.
I take the carburator off and put on one of my spare rebuilt Ford EBU carbs.
I start the engine. No change. I pull the valve covers again to look at the push rods again (I had not glued the cork gaskets with RTV Blue when I put them back on earlier). Still no problems with push rods.
Only thing I haven't checked is compression, but I doubt this is a good symptom here due to two or more cylinders simultaneously failing to fire all at once. Sounds like and ignition problem to me.
So now I have just finished removing all the old spark plug wires and brackets. I took a new set of Y-block spark plug cables I got from Macs and put the old rubber mounting grommets and metal brackets on them and wormed the cable sets under the dual exhaust manifolds and bolted the brackets back on to the engine block. Boy those brackets in the back are not much fun even for a skinny wiry guy like me, but it is done.
I didn't get a chance to start engine as it got too dark and i was exhausted. Will probably try it tomorrow sometime.
My guess is if this doesn't work, I may have installed a brand new point set and/or condenser that are bad.
Anybody seen the new point sets the chinese are selling for the loadomatic dizzy's? They have a very shallow contact on the point arm, while the contact on the stationary base is twice as thick.
I have already gotten a couple of new sets of points from NAPA that have the point contacts configured the OEM design just in case.
More tomorrow.

 

[mobileparts]

NAPA stands for "Never American Parts Available "....

I have some top quality yesteryear ***:U.S.A. made *** Points for the 1954 - 1956 Ford application, as well as, Condensers, Rotors, and Distributo Caps, and Motorcraft Spark Plugs... if you would prefer....,

Always best to simply call me --- 516 - 485 - 1935..... Craig.....

 

[KULTULZ]

NAPA stands for "Never American Parts Available "....

I have some top quality yesteryear ***:U.S.A. made *** Points for the 1954 - 1956 Ford application, as well as, Condensers, Rotors, and Distributo Caps, and Motorcraft Spark Plugs... if you would prefer....,

Always best to simply call me --- 516 - 485 - 1935..... Craig.....

What this board needs is an 'APPROVED VENDOR LISTING' whereas small and quality vendors can advertise.

Stuff is starting to dry up.

 

[40cpe]

Years ago we had similar symptoms with a '55. Turned out to be the ignition wire under the distributor plate had a bare spot. I hope you find your problem soon.

 

[rotorwrench]

The better a person knows their old vehicle the better they learn to troubleshoot it. ALWAYS check the easy things to do first. A condenser is a good first call but, as was mentioned, the vulnerable parts of the ignition coil circuit are important too. That rotor clip is also a good call. I've had a problem or two with those.

Next is fuel delivery. Does it have pressure? It doesn't take long to see if fuel is getting to the carb. See if the bowl is full by testing the accelerator pump.

A compression test will tell you a lot. If valves are sticky or out ot time as well as ring & piston condition can be tested. Check the plugs with a tester while their out if you can. Test each with their respective plug wire if you have someone to crank while you check.

The coil can be checked with an Ohms meter and the ignition switch wire with a volt meter.

You'll find it but I suggest easiest ways for checking things first. It works for me.

 

[Daves55Sedan]

Years ago we had similar symptoms with a '55. Turned out to be the ignition wire under the distributor plate had a bare spot. I hope you find your problem soon.

Why would it matter if one of the wires under the breaker plate was grounded? Aren't those both ground wires anyway?
Primary wire from points to + side of coil is ground, although it is an insulated wire, right? The other wire comes from the factory bare. It connects to baseplate of points and distributor housing on the other end.

 

[Daves55Sedan]

I had changed all the spark plugs too, along with all new ignition cables, so it's not a spark plug problem.
I shot some carb cleaner down the airtube which goes into the float bowl. It all ran out in between the valve body and main body of the carburator near the left passenger side. Makes me wonder if my power valve is hitting the bottom of the vacuum chamber due to it's gasket being too thick. So now I'm taking carburator off to check and test for leaks before I go any further, but this is not anything that should prevent plugs from firing. I will also fill the float bowl while it is off the intake to make sure gas isn't leaking down the throat with the accelerator linkage in idle position.
The car has an old cast epoxy coil (6-volt), that I installed back in the mid '80's. It's got a zillion miles on it. Are these prone to failure after a given time period or mileage?

 

[scicala]

To test the condenser, all you have to do is just disconnect the wire on it for a couple of minutes. Shouldn't pit the points in that short of a period.

Sal

 

[40cpe]

Why would it matter if one of the wires under the breaker plate was grounded? Aren't those both ground wires anyway?
Primary wire from points to + side of coil is ground, although it is an insulated wire, right? The other wire comes from the factory bare. It connects to baseplate of points and distributor housing on the other end.

The wire from the distributor isn't grounded until the points close. It is insulated 'till that time to allow the coil to build a charge.

 

[dmsfrr]

Why would it matter if one of the wires under the breaker plate was grounded? Aren't those both ground wires anyway?
Primary wire from points to + side of coil is ground, although it is an insulated wire, right? The other wire comes from the factory bare. It connects to baseplate of points and distributor housing on the other end.

The wire from the 'distributor' side of the ignition coil does go thru the points to ground. But... the switching action of the points turns the coil on and off at very short and very specific times during the rotation of the distributor, so the high voltage spark is timed with the position of the rotor at one of the plug wire contacts in the distributor cap.
The correct min & max Dwell spec is only a couple degrees, same with the points gap if using a feeler gauge. Set the points / dwell before setting the timing.

If the wire from the coil to the points is damaged (intermittently 'open'), has a poor connection, is frayed or grounding somewhere it shouldn't be the spark created by the coil won't be synchronized with the rotor position inside the cap.

If the Ground wire from the points to the distributor housing is loose or damaged, it can have the same inconsistent effect on the synchronized timing of the high voltage spark from the ignition coil to the distributor, rotor and spark plugs.
Photo 3 example broken ground wire, only 2 strands remaining.

Ignition Timing? Possible Vacuum Leak?
With Loadomatic distributors the Only thing that advances the timing is proper operation of the vacuum canister turning the mounting plate for the points.
If carb vacuum doesn't turn the plate due to a failed or leaking canister, or it's stuck, the ignition timing will not advance.

One or two of the symptoms you mentioned are similar to a vacuum leak. Test the distributor canister & plumbing.
.

 

[rotorwrench]

If the breaker side isn't well grounded then there is nothing to break. If a condenser won't hold a charge then the ignition wont work well at all. A leaky condenser will give intermittent problems and breaker point wear. The points will ark all over the place if the condenser won't take the in flow or back flow during the induction process.

A sticky valve only has to be slow to close to be problematic. This may not bend a pushrod since it closes but takes a bit too long to do so. Running Marvel Mystery Oil in the fuel will usually clear this stuff up.

A leaky suction line in the fuel system will draw air in and a plugged vent in the fuel tank or cap will cause starvation. Stuff like this can be hard to pin point some times. If crud got into the carburetor through the system then that could be plugging things off.

 

[55blacktie]

Crack in the distributor cap? Is the rotor making good contact with the cap?

 

[56 Panel]

If it were me, I would make sure the rocker arm assemblies are ok,
check the valve clearances, and check compression. Hope this helps.

 

[KULTULZ]

IMO ...

You need a spark testing tool ($10.00) to find the misfire(s) and then diagnose from there (if it is IGN). Even a timing light can be used to locate a misfire.

POST #10 is correct as to the DIST.

I had one of these these testers years ago that was GENUINE CHAMPION (USA) ...

... but my little light went out ... ...​

 

[Flathead Fever]

I was ASE Master Mechanic for 30-years. At home you're at a disadvantage without an ignition scope. To see if the problem is only one, some or all cylinders.

A couple things you can try at home is pulling one plug wire at a time and see if effects the rpm. Do not do this with electronic ignitions because it can damage the electronics. Take the wires loose and just set them back on the plugs so they make contact but you can easily remove them with your best insulated plyers. If the rpm drops as you remove each wire it will tell you the cylinders are firing and if they do not drop they are not firing. If it's an overall ignition problem the timing mark will be dancing around if all cylinders are misfiring. Make sure you have the proper voltage to the coil, check it with the points "open" or the wire disconnected from the coil. You will not get a reading if the points are closed Like others have said, check that wire from the coil to the points to make sure it is not broken or grounding out.

If the vacuum advance were to fail it would not cause a misfire, especially at idle and wide-open throttle when it does not work at all. It would run sluggish under part throttle without the advance but not misfire. If the diaphragm failed the vacuum leak would not be large enough to effect it at 35 mph. And there is no vacuum to it at idle because it uses ported vacuum and not manifold vacuum. If you want to check its operation you can remove the cap and push the diaphragm in and stick your finger over the vacuum port and it should remain there until you remove your finger. Then with the line still disconnected start the engine and raise the rpm off of idle until you feel vacuum at the line, hook it back up and the rpm should increase. The vacuum advance is there to advance the timing under part throttle but it's also there to retard the timing under heavy loads. The engine cannot handle full advance under wide open throttle, with regular octane fuel. The engine will ping because of the increased cylinder pressure. Because the vacuum drops off to zero during wide-open throttle, the vacuum advance rotates the plate back, which retards the timing, this prevents pinging, pretty ingenious of those engineers. A vacuum leak would need to be pretty large to effect an engine at 35 mph. It's possible, especially if it sucked an intake gasket on the lifter valley side of the intake. I don't know anything abut 292s. I'm into flatheads and 289/302s. I assume this has a road draft tube. Plug off the tube and pull the oil fill cap. If it sucked an intake gasket inside the engine there will be a vacuum at the oil fill tube, it will suck a piece of paper down against the tube instead of the blowby pushing it away. In my entire career I only saw that happen one time.


If you want to check the valves, hook up a vacuum gauge and you should see a steady reading. While you had the valve covers off you could have disabled the ignition and cranked the engine while you watched all the valves open and close. Look for broken valve springs and all the valves opening the same amount. Don't try it running or it will throw oil all over the place.

If you think its fuel, spray some carb cleaner or starting fluid in it and see if that makes it happy.

 

[KULTULZ]

I was ASE Master Mechanic for 30-years. At home you're at a disadvantage without an ignition scope. To see if the problem is only one, some or all cylinders.

DAMN! ...

That was a good write-up ...

 

[Daves55Sedan]

I'm aware of using a timing light to determine individual plugs not firing. In this case, I cant do that. The engine wont idle with this many dead cylinders, it just dies. I'm aware of how to test vacuum advance, but I use a mityvac to test it. It is good. And even if the vacuum diaphragm was busted, it would still idle normally, so I'm not worried about that.
I did find that the power valve in the carburator was too deep in that it was resting up against the vacuum chamber in the valve body when it was fully assembled with its gasket. I found a more shallow power valve and put a new gasket on the power valve and a new gasket between carb main body and valve body. The old gasket was pretty well crushed. I also checked to see if the new power valve leaked prior to assembly onto the valve body. Gas does penetrate the the outside of the power valve gasket, but it won't develop a drip over several hours, so I put it back together and installed the carb back on the intake. That carb is clean and pristine as can be.
I did inspect the valve pushrods and springs when I had the valve covers off. There appears to be no broken springs and no bent pushrods. The valve lash on all valves looks within specs .019, but that is slo-cranking engine one cyl at a time.
Next I am going to take out the dizzy and inspect the distributor to coil wire. I am also going to replace the chinese points with a better set of new points (with the contacts placed per OEM) that I got from NAPA and set the gap with a feeler guage. After that, I will check to see if there is a consistent coil output.

 

[Daves55Sedan]

Today I charged some batteries to use in my multimeter so I could test my condenser and ignition coil. First, I cranked the engine to get Piston #1 at TDC and both valves closed. The ignition rotor was pointing to spark plug #1 tower. So far so good. Then I looked down at the timing pointer. The TDC mark on the crankshaft damper was about 1-1/2 inches past the TDC mark. So the timing chain must have left the camshaft behind a notch or two. I had checked this before, but it looked right.
Looks like I will be needing new timing chain and sprocket set.
I started looking, and everyone seems to be out of stock on timing sets for a Y-block.
I looked at Rock Auto, whom I had never made a purchase from before. They claim to have a Melling brand chain and sprockets. Can any one attest to the quality/accuracy of their stuff?

 

[KULTULZ]

... Melling brand chain and sprockets. Can any one attest to the quality/accuracy of their stuff?

MELLING is good stuff (IMO), but I would find out what TED EATON prefers. He is the guru ...

 

[dmsfrr]

... I cranked the engine to get Piston #1 at TDC and both valves closed. The ignition rotor was pointing to spark plug #1 tower. So far so good. Then I looked down at the timing pointer. The TDC mark on the crankshaft damper was about 1-1/2 inches past the TDC mark. So the timing chain must have left the camshaft behind a notch or two. ....

It's possible but unless you have a solid metal crank pulley, it's maybe even more likely the rubber layer (red arrows, example photo) that holds the weight ring in place has failed, letting the outer ring & its timing marks slip out of position.
.