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Discussion Starter #1
Hi Guys,

I have attached photos of my spark plugs. Looking for any feedback and if any adjustments are required?

Car is a 74 spider with Weber carbs, Motronic high compression pistions and C&B cams and electronic ignition.
 

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Burning oil on #1.
 

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Does your intake manifold have a little nipple on the #1 cylinder that looks like a little tiny hose goes on it? It's a vacuum port and might have something to do with what you are seeing. If it is open I suspect it might cause a leaning of the mixture on #1?... Just brainstorming but I suspect it if it is there it would contribute to this anomaly. I'm not an expert on this .. just a facilitator. I know some guys plug it when it has no function with a vacuum advance Distributor.
 

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there is a limit as to what you can learn from plug color unless you do a series of proper plug chops.
 

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either oil or rich mix.
 

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Bring the #4 piston up about midway in the cylinder and look down through the spark plug hole to the top of the piston. Compare cylinder to cylinder.

Some conventional wisdom says to get a good spark plug read, get the engine warm then do a series of full throttle accels, then shut the engine off and pull/inspect the plugs.
 

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If it were my car, and the plugs looked like that, I would think they look fine - expect the one mucky one. If the mucky one is #4, I would assume seepage from the head gasket at the return galleys was causing it, and look for further evidence of this before anything else.
Agreed 100%. plugs look good with one exception. How is the compression across the board? Perhaps the oil ring on cyl. #4 did not seal or ring end gaps are not aligned correctly
 

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Discussion Starter #10
Photos I posted are from yesterday, after an hour drive.

Yesterday before my drive, I also changed the main carb jets from 115 to 130. Car seems to run better and freeer.

Today I cleaned the #4 plug and went out for a long day trip about two hours each way and 200 miles or so.

See photos of the #4 plug after today's drive.
 

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Frank, have you tried swapping #4 plug with one of the others for testing purposes?
 

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Pete's thinking ignition. Could be. Also bad plug wire or connector in cap or to plug.
 

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Looks like oil burning. Put in a NEW PLUG & change the plug wire from another plug. Could be a valve guide seal. Or rings. How does the exhaust look while the engine is running.
 

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Discussion Starter #16
I do get a bit of greyish smoke when I put my foot down. Nothing at idle.

Still guaging oil consumption on this new engine. Maybe about half a quart every 500 miles.
 

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1/2 qt. in 500 miles. That is a lot of oil. I have only rebuilt 4 car engines and one motorcycle engine. And non have ever used oil like that.
 

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What size engine is it?
What size chokes?
What code Webers?

Photographically, it may be worth helping the camera/phone to focus on the plug by placing something (e.g. your hand or something with printed text) to the side of the plug. A sharper focus will show up the deposits more clearly.
 
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