MGB & GT Forum

This is plug #3, and typical for all four plugs. This looks ok to me for air/fuel mixture tuning.
HS4s. Idle set at 950 rpm. CEI ignition with port advance.

However, I’m not sure what they tell me about my present ignition timing setting (strobe @ 14°) - too advanced, not enough advance, etc.

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It is easier to fight for one's principles than to live up to them.

When you worship power, compassion and mercy will look like sins.

How does your car run? Good or bad? Plugs look good. If you think you have a timing problem, just time it by ear. Find the right spot that it runs the best. Don't make it complicated.It's easy.

My timing changes with rpm. What rpm was the engine running at?

Adrian

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Home built Eaton M62 Supercharger with 8psi boost, 8:1 compression, custom "supercharger" cam from Schneider Cams, Mikuni HSR48 Carburetor, custom ground high ratio "stock" rocker arms, Maxspeeding rods with Teflon wrist pin buttons, custom aluminum cold air intake, CB Performance computerized ignition, Fidanza 9 pound flywheel, 1.44 exhaust valves in 48cc chamber head, matched manifolds, 2 1/4" exhaust system.

Spark plug readings will show if you are too far advanced but not much before that.

Do you see any evidence of that here?

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It is easier to fight for one's principles than to live up to them.

When you worship power, compassion and mercy will look like sins.

Car runs fine. No timing problem of which I’m aware, just looking to see if the plugs suggest otherwise.

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It is easier to fight for one's principles than to live up to them.

When you worship power, compassion and mercy will look like sins.

My timing works that way too.
Normal rpm range - 0 to 4500 ish rpms.

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It is easier to fight for one's principles than to live up to them.

When you worship power, compassion and mercy will look like sins.

Looking at spark plugs pulled after the engine has been idling tells you nothing about timing or mixture at cruising speed/under load.

Do the test again and post pictures after a 100kph run under moderate throttle, say when pulling up a hill, but kill the ignition and coast with your foot on the clutch. That is, the engine dies immediately so no fuel is ingested and unburnt.

Then you'll get a far more realistic example of how the engine is running.

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Semi retired Auto Electrician with over 44 years experience. Specializing in pre 1975 car electrical systems. Trained on early Lucas, Bosch and Magnetti Marelli systems.
Australian Auto Electrician actively rebuilding and calibrating early Lucas and Delco Remy 1/2/3 bobbin regulators, Lucas generators/alternators (including 3rd brush and generator/starters) and magnetos. Large supply of original Lucas 1960 and 1970's parts to suit British cars (assembled and/or exported).

Available for guidance/assistance via email.

Be warned......I'm an grumpy old fart. I take no **** from people too lazy to do a preliminary search of the forum or google so therefore don't deserve my time.
Nor do I appreciate wasting time providing suggestions towards a solution to then have you ignore them because you have to do some actual investigative work, in favour of a possible solution from a knowall friend of a friend of a friend who once upon a time was a gardener with a shifting spanner and a set of pliers and somehow pretended they'd fixed their glowing ignition lamp with a piece of surgical tape, speck of moon dust, a scratch of their arse and a rusty razor blade.

And having said that, please don't mistake me for someone who even remotely cares what you think.

The plugs look like the mixture is a bit weak. I like to see the central insulator slightly brown. Not by much though. MGB engines like to run a bit rich. But the engines in later US cars had to meet tougher emissions standards than here in the UK. This required tighter control of the mixture etc. That might be changing the picture regarding your car.

Look for past posts. I put a link somewhere on reading timing and heat range on the plugs. You can GOOGLE it too. How far down on the lead should the band be was the parameter.
Timing is better set with a microphone and headphones to listen for Ping, then back of a couple of degrees. Just listening for ping over road noise is not very accurate. Then yo get a number you canuse your light to repeat.

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Cogito ergo sum periculoso

Your plugs look fine for whatever rpm and load they were under... at the time. Your car probably idles at 15 degrees, cruises at 40 something and is at 34 or so under full throttle... and everywhere and anywhere in between, at different speeds/loads. If it was even possible to tell the timing from looking at the plugs you would have to do quite a few tests to see what it was doing at all those different loads and speeds. (don't forget the timing varies under load vs not under load, at the same speed)
You can determine the correct timing and mixture at maximum speed by seeing how fast the car can go flat out. If you vary the timing and it goes faster, the timing is better, etc.

Same with mixture. If you want to know just get a wide band A/F meter. My car drops a full point at cruise just by flicking it into overdrive. Read that on a plug.

Adrian

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Home built Eaton M62 Supercharger with 8psi boost, 8:1 compression, custom "supercharger" cam from Schneider Cams, Mikuni HSR48 Carburetor, custom ground high ratio "stock" rocker arms, Maxspeeding rods with Teflon wrist pin buttons, custom aluminum cold air intake, CB Performance computerized ignition, Fidanza 9 pound flywheel, 1.44 exhaust valves in 48cc chamber head, matched manifolds, 2 1/4" exhaust system.





Edited 1 time(s). Last edit at 2018-09-16 10:48 AM by pinkyponk.

All interesting stuff. I never heard of using a microphone to detect knocking. But I guess it could be made to work.

How about fitting a knock sensor from a modern petrol engined car? They seem to be available for around $50. But how to use it without fitting an oscilloscope or similar. Just a warning light would be enough. I assume they use something like a piezo-electric crystal like you find in some gas lighters. They generate electricity when compressed.

What is an wide band A/F meter?

Dave (or anyone else) - Can you elaborate on what evidence of too advanced could be seen on a plug? I can't come up with timing thing would show in plug color. Maybe too black for severe retard [but of course the temperature would be elevated, possibly better combustion anyway. Explain?

The timing at just shy of pinking is not necessarily the optimum timing for power. For that you need a dyno or a top speed run, or an elapsed time between measured points. An A/F meter (air/fuel) displays the air/fuel ratio on a dial in real time.

Adrian

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Home built Eaton M62 Supercharger with 8psi boost, 8:1 compression, custom "supercharger" cam from Schneider Cams, Mikuni HSR48 Carburetor, custom ground high ratio "stock" rocker arms, Maxspeeding rods with Teflon wrist pin buttons, custom aluminum cold air intake, CB Performance computerized ignition, Fidanza 9 pound flywheel, 1.44 exhaust valves in 48cc chamber head, matched manifolds, 2 1/4" exhaust system.

Frank's plugs look just dandy. If anything, I'd fatten the carbs up a flat or two, but he's very close.

An indication of way over-advanced timing would be spatter on the plugs (and on the pistons as well). The appearance is like you would see if tiny droplets of liquid solder were sprayed around randomly. If such spatter is seen, engine failure is not far behind...

Dick

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Errabundi Saepe, Semper Certi
(Often wrong, but always certain)