Improvised oscilloscope probe for Automotive ignition analysis.

[Johnny10]

If you are helping to solve the engine mystery than you should have something to bring to the table.
An engine misfire is a symptom of a problem with Fuel, Spark or Compression.
You seem to have fixed your sites on Spark, yet after completely changing the ignition system you still have misfire.
This is a distributor type ignition, besides the electricity flowing to the spark plugs there are also mechanical issues to be addressed.

I hadn't realized that this Grey Motor has cult status in the Australian Racing world.

You should be able to find lots of information about every aspect of this engine.
Actually in the short time I researched the engine I found tons of information.
This engine was tuned for performance over quite a number of years.

I enjoyed acquiring the knowledge and collecting and building all the tools to know what was really happening in my engine.

I was never much for parts changing as a repair technique.

You are on an adventure, good luck, get in there get your hands dirty.

[joeqsmith]

Also, the missfire was there with the first (or original) engine in the car when it was first acquired. So, much more than ignition components have been swapped. I might have already mentioned this, but the triple 11/2 SU carbs were swapped for a single (forgot the brand) carb and a new manifold fabricated out of two, all in an attempt to fix this miss fire.
The engine was swapped as this one was being modified extensively for performance and the original one was being used meanwhile.

Would be funny if the fuel pump or the cell was the problem.   Maybe all their high load testing is at the track instead of on the dyno and there's no baffles in the cell.  Maybe they are pumping air...  Maybe the pickup in the cell doesn't stay where the fuel is...

I had similar problems with oil.  It tough to keep fluids where you want them.  After several baffle and pickup designs I sorted it out....  With data logging...  (Add fuel pressure to that list as well)

[Jim-0000]

.............................
Would be funny if the fuel pump or the cell was the problem.   Maybe all their high load testing is at the track instead of on the dyno and there's no baffles in the cell.  Maybe they are pumping air...  Maybe the pickup in the cell doesn't stay where the fuel is...
..............................

What is the "cell"? Is that what we would call the tank? I assume it is. This car is fitted with a tank designed specially for racing.
The car has been on the dyno twice. The same symptoms occur there as on the track.
I don't know how fuel flow is, or could be, data logged.
Thanks for the post.

[Jim-0000]

If you are helping to solve the engine mystery than you should have something to bring to the table..................

I mentioned in an earlier post that I have been suggesting that solid core plug wires should be fitted to replace the common type suppression leads on the car (core type unknown), for some weeks now. There has been resistance and all of it is not in the car! (pun intended).
Somewhat reluctantly, the owners have ordered a set of solid cored ones as described above.
Also, I now have arranged the loan of an oscilloscope and suitable probes with which to do an ignition analysis should the new leads not solve the problem.
I don't have anything else to "bring to the table".
Meanwhile, the owners brother is talking about the problem still being induction related. Even though two very different carburettors and manifolds have been fitted and tried.
But for all I know, he may be on the right track as I am out of my experience and skill range here.

............................. yet after completely changing the ignition system ..........................

Not quite. See above.

Thanks for your encouragement.

[joeqsmith]

.............................
Would be funny if the fuel pump or the cell was the problem.   Maybe all their high load testing is at the track instead of on the dyno and there's no baffles in the cell.  Maybe they are pumping air...  Maybe the pickup in the cell doesn't stay where the fuel is...
..............................

What is the "cell"? Is that what we would call the tank? I assume it is. This car is fitted with a tank designed specially for racing.
The car has been on the dyno twice. The same symptoms occur there as on the track.
I don't know how fuel flow is, or could be, data logged.
Thanks for the post.

Yes, the tank that holds the fuel.   
https://www.onallcylinders.com/2013/03/25/monday-mailbag-fuel-cells-vs-fuel-tanks/

To record the pressure I just put a sensor right in the fuel distribution block.   

[dardosordi]

Hi, I had a similar issue in my Ford EcoSport. The mechanic replaced sparkplugs, leads, carburetor an the failure persisted. I scoped it, used OBD scanner and could not figure it out.     

The mechanic suggested changing the oil the manufacturer recommended for a thicker one. All fixed.   

[Edison]

Hi, I had a similar issue in my Ford EcoSport.

Ford ekosport had so-called hydroshells to control the clearance of the valves - there was an absolute need for oil with a specific viscous number. Other oil = other dynamic pressure = malfunction hydra = changing valve clearance = irregular operation.

[Gregg]

Now that we know more about the engine being a vintage Holden Grey, we may be able to narrow things down a bit.  As far as “taking it elsewhere” is concerned, that is hardly in the spirit of the EEV blog forum even if it turns out not electrically related.
An intake manifold modified from the horrors of triple SU carbs to an unknown single carb is certainly suspect for vacuum leaks; which would fit the description of symptoms.   Not that triple side draft carbs don’t have their advantages; multiple SUs need a lot of fiddling to tune properly and to keep in tune.  Jaguar certainly liked multiple SUs and they ran quite well when in tune.   Single carburetors on inline sixes have always had issues with cylinders 1 and 6 getting a proper fuel mixture at all RPM and engine load conditions due to the longer runner length; generally this is overcome by running a richer mixture to the other cylinders to compensate. 
Next on my list of possibilities would be valve train problems.  Rocker arm wear and misalignment are particularly hard to diagnose without taking it all apart.  Are the lifters solid or hydraulic and matched to the cam profile? The oil pump and distributor are driven off of the back portion of the camshaft and wear, misalignment or loose timing chain are possibilities. 
Another possibility, although remote, is head gasket sealing; the head stud layout in the Holden isn’t optimal for keeping a good head gasket seal in performance engines.

[Jim-0000]

Now that we know more about the engine being a vintage Holden Grey, we may be able to narrow things down a bit.  As far as “taking it elsewhere” is concerned, that is hardly in the spirit of the EEV blog forum even if it turns out not electrically related.........

I am glad you agree!

An intake manifold modified from the horrors of triple SU carbs to an unknown single carb is certainly suspect for vacuum leaks; which would fit the description of symptoms.   .................

The carburettor is a Holley. The intake manifold was fabricated from two manifolds to suit the carb and the head. It was professionally welded and machined flat etc. New gasket fitted. Zero chance of leak, all who have looked at it agree.

Rocker arm wear and misalignment are particularly hard to diagnose without taking it all apart.  ..............

Brand new roller rocker gear is fitted (at great expense!). Problem here? Most unlikely I suspect.

Are the lifters solid or hydraulic and matched to the cam profile? ......

I don't know. I would assume the lifter are solid, but not at all sure. I will find out later this week.

 
Another possibility, although remote, is head gasket sealing; the head stud layout in the Holden isn’t optimal for keeping a good head gasket seal in performance engines.

Cooling system pressure test has been done a couple of times. The head stud layout tip is one worth some consideration.

Current prospects and plan:

1. Fit solid core ignition leads (plug leads) when they arrive in the mail.
2. If problem persists, do a full oscilloscope investigation of the ignition system. Now we have the equipment available.

Thanks for the posting.

[vk6zgo]

Now that we know more about the engine being a vintage Holden Grey, we may be able to narrow things down a bit.  As far as “taking it elsewhere” is concerned, that is hardly in the spirit of the EEV blog forum even if it turns out not electrically related.........

I am glad you agree!

An intake manifold modified from the horrors of triple SU carbs to an unknown single carb is certainly suspect for vacuum leaks; which would fit the description of symptoms.   .................

The carburettor is a Holley. The intake manifold was fabricated from two manifolds to suit the carb and the head. It was professionally welded and machined flat etc. New gasket fitted. Zero chance of leak, all who have looked at it agree.

Rocker arm wear and misalignment are particularly hard to diagnose without taking it all apart.  ..............

Brand new roller rocker gear is fitted (at great expense!). Problem here? Most unlikely I suspect.

Are the lifters solid or hydraulic and matched to the cam profile? ......

I don't know. I would assume the lifter are solid, but not at all sure. I will find out later this week.

 
Another possibility, although remote, is head gasket sealing; the head stud layout in the Holden isn’t optimal for keeping a good head gasket seal in performance engines.

Cooling system pressure test has been done a couple of times. The head stud layout tip is one worth some consideration.

Current prospects and plan:

1. Fit solid core ignition leads (plug leads) when they arrive in the mail.
2. If problem persists, do a full oscilloscope investigation of the ignition system. Now we have the equipment available.

Thanks for the posting.

If it is a grey motor it will almost certainly have solid lifters.
The modifications necessary to fit hydraulic lifters would be so profound that most people would just ditch the "grey" & go for a "red" motor.

[Jim-0000]

[/quote]

If it is a grey motor it will almost certainly have solid lifters.
The modifications necessary to fit hydraulic lifters would be so profound that most people would just ditch the "grey" & go for a "red" motor.
[/quote]

Yes.
Thanks for the post.

[floobydust]

If there is a vacuum port right at the carburetor, you can connect a MAP sensor + scope and observe the vacuum dips for each cylinder, what the carb sees. Or add a port to the intake manifold.
I'm thinking about the intake manifold volume and uneven pulsating flow because the runners are different lengths - some carbs freak out if the vacuum-ripple is great.

[Circlotron]

Posting so I get updates.

[Edison]

If there is a vacuum port right at the carburetor, you can connect a MAP sensor + scope and observe the vacuum dips for each cylinder, what the carb sees.

This is the principle management Ecotronic, in my case, the sensors were four - the vacuum was compared in different chambers (the Weber double carburetor).
Your carburettor is not equipped with an electric needle choke?

[Gregg]

1948 Chev pickup

If there is a vacuum port right at the carburetor, you can connect a MAP sensor + scope and observe the vacuum dips for each cylinder, what the carb sees. Or add a port to the intake manifold.
I'm thinking about the intake manifold volume and uneven pulsating flow because the runners are different lengths - some carbs freak out if the vacuum-ripple is great.

Floobydust: that is an interesting electronic troubleshooting method for a mechanical problem 
Another troubleshooting method, more old school, is to pull or short the plug wires one at a time when the engine is running rough to see which cylinder(s) are least affected by no firing.  This may narrow down the search. 
Knowing the model of Holley carb may help us; each carb has its own quirks.   Is this the Holley 32/36 copy of the Weber design?
The vacuum leak test is still a good idea.  At low idle, lean out the carburetor as much as you can and still have it running and spray some flammable carb cleaner at all gasketed intake areas and at all welded areas to see if the RPM rises.  You can test your setup by squirting a tiny amount into the carb intake and noting the result.
Two weeks ago I was helping a friend with a with a 1948 Chev pickup with a single throat Carter “rebuilt” carb and it was having similar symptoms.  Installing the idle jet and emulsion tube assembly from the original carb solved the problem. 

[vk6zgo]

My Holden EH's Stromberg carby back in the day, was inadvertently fitted with the main jet from the grey motor.
All worked OK, except that every now & then, the thing would hesitate, & sometimes stall.
I got a carby overhaul kit from the Auto section of my old work, & they asked :- "Do you want the full kit?"

The difference was that kit had a correct replacement jet---- sneaky way of avoiding a recall!
Fitted it, & no more problems.

Holden had a bit of a "glitch" around that time--- someone decided the "grey motor" clutch was adequate for an engine with 30% more power.
Sometimes it was, but mine kept killing clutch plates.(granny-v-revhead?)
I ended up fitting the clutch assembly for the higher power "179cu in" option.

[floobydust]

To find vacuum leaks, I use propane. Take a blow torch or BBQ tank (after low pressure regulator) and a long hose, 1/4" tubing with a metal wand and move that around the seams. Enough propane to supply say a candelabra, just a little flow.
You can easily find leaks, the RPM's jump right up. Test it by holding the wand at the carb inlet, letting propane in and see the tach jump up.

[maginnovision]

To find vacuum leaks, I use propane. Take a blow torch or BBQ tank (after low pressure regulator) and a long hose, 1/4" tubing with a metal wand and move that around the seams. Enough propane to supply say a candelabra, just a little flow.
You can easily find leaks, the RPM's jump right up. Test it by holding the wand at the carb inlet, letting propane in and see the tach jump up.

I've always used carb cleaner, like Gregg. It's usually much more handy for me than propane.

[Jim-0000]

Thanks for the good replies.
The carburettor cleaner tip for chasing vacuum leaks is a good one. However, it is not applicable in this case.
We are still waiting for the new plug leads. I expect them one day this week.
There will be no work on the Holden until they arrive and we try them.

[Jim-0000]

Just to clarify; the owner and brother are sticking to just changing one thing at a time and then testing it before trying something else. For obvious reasons; they dearly want to know what is the reason for this problem.
Seems logical to me, so I am not arguing.

[Jim0000]

I am just posting to say I have no positive news to report about this engine problem.
In fact, the problems have just compounded along the way. The second camshaft is starting to fail in this engine. They are loosing lobes gradually for no apparent reason, thereby making the tappets increasingly noisy and filling the oil with fine, case hardening steel fragments.The lifters were re-faced each time.

The owners (and me) are all stumped!

[Jim-0000]

Both problems have been identified and fixed on this engine.
The miss-fire was caused by an induction problem. The carb was rotated (again) this time @ 90 deg. And the engine ran smoothly. The owners brother has being saying for some time that this was the problem, and it turned out he was correct.
The problem of the camshaft lobes failing (wearing away very rapidly with all sorts of problems resulting) was due to a mis-match of cam and cam followers.
A ground standard Holden grey motor cam shaft was fitted, but Falcon cam followers were used.
Holden and Falcon use a different method to rotate the followers:
1. Holden have the followers slightly off centre with relation to the cam lobes.
2. While, Falcon have a very slightly concave top and the cam lobes are ground with a slight taper - in the direction of the axis of the shaft.

The fix was to grind the shaft again, and re-face the followers flat.
At least, I think that is what they did. I will ask again next time I see one of the brothers who have been working on this.

Of course, the engine had to be flushed out as good as possible and the filters changed. There would be metal fragments in the oil!............

[Circlotron]

Though it was first used in 1948, the Holden grey motor is basically a 1920's design. That's not to disparage this old timey donk - quite the opposite. It's surprising just how much technology and hidden engineering detail went into these old things, while being superficially dirt simple, made it something that suitably maintained would run reliably for decades.

[Jim-0000]

Yes I agree.
The only thing that I don't like about it, along with the later Red Holden motor, is the rope main bearing seal!
From memory, the owners modified it to take a two part modern silicone seal.
I know they did that on the turbo charged mark 3 Zephyr they are running in another car.

[Circlotron]

Don't forget shared inlet ports, and on the grey, shared exhaust as well.
Fibre cam gear.
And the red motor has the fan belt in a groove around the perimeter of the harmonic balancer! For it to do it's job properly there should be nothing touching it. Sounds like a bean counter overruled an engineer on that one...