Evaluating Spark Plugs

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Mark Osterman
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Evaluating Spark Plugs

Post by Mark Osterman » Sun Jul 28, 2019 8:41 pm

Been wrestling with the fuel input in the U&J carburetor and checking everything in the fuel and electrical systems. I usually drive with the spark advanced pretty far except when climbing hills and the gradually advance as I gain speed. Here is one of the vintage Champion X plugs. They all look pretty much like this. I keep a thin Barber dime on my key chain as a thickness gauge.
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Re: Evaluating Spark Plugs

Post by Ruxstel24 » Sun Jul 28, 2019 8:47 pm

Mark,
You need to look at the porcelain inside.
It looks good from that shot, maybe a little lean.


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Re: Evaluating Spark Plugs

Post by Mark Osterman » Sun Jul 28, 2019 8:57 pm

Yes, they look good on the porcelain. Didn’t take a picture. I think most people who drive Ts have pretty sooty plugs from short drives and too rich a mix.

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Re: Evaluating Spark Plugs

Post by Ruxstel24 » Sun Jul 28, 2019 11:30 pm

Here's a pretty good chart I found on the interweb.
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Re: Evaluating Spark Plugs

Post by John E. Guitar » Sun Jul 28, 2019 11:54 pm

NGK have a video on reading spark plugs here:

https://youtu.be/uMYAEtxiYfc

They have some good technical information here:

https://www.ngk.com.au/technical_info/analysis/

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Re: Evaluating Spark Plugs

Post by Steve Jelf » Mon Jul 29, 2019 12:50 am

I would measure that dime and be sure it's close to .03125".

IMG_2556 copy.JPG
IMG_2558 copy.JPG
The only real spark plug test I know is to see how they fire under compression.

Champion X plugs are great, but if they're assembled too tight or not tight enough they can go south on you. Cary plenty of spares so you don't have to limp along on three cylinders when a plug fails.
The inevitable often happens.
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Re: Evaluating Spark Plugs

Post by Charlie B in N.J. » Mon Jul 29, 2019 6:52 am

you're running lean as hell.
Forget everything you thought you knew.

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Re: Evaluating Spark Plugs

Post by Charlie B in N.J. » Mon Jul 29, 2019 6:52 am

you're running lean as hell.
Forget everything you thought you knew.


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Re: Evaluating Spark Plugs

Post by Mark Osterman » Mon Jul 29, 2019 10:36 am

I’m still trying to get more gas into this carb. I’m using the remote choke control now .. see picture. I’ll clean the plugs and inspect them again after an hour long drive.
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Re: Evaluating Spark Plugs

Post by Mark Osterman » Mon Jul 29, 2019 12:04 pm

Hmm ... wonder if I have an intake leak. It was difficult getting the gaskets just right this last time. That might solve the heat and anemic fuel problem.

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Re: Evaluating Spark Plugs

Post by RajoRacer » Mon Jul 29, 2019 12:37 pm

What are you using for gaskets, Mark ? Did you remove the exhaust manifold to gain easier access to verify the intake seating ?


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Re: Evaluating Spark Plugs

Post by Mark Osterman » Mon Jul 29, 2019 1:24 pm

I always use the individual copper asbestos rings and steel glands. The valves were good ... this is a rebuild from three years ago. But you never know. I’ll remove the manifolds this weekend and take a look. An intake leak could answer everything.


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Re: Evaluating Spark Plugs

Post by Scott_Conger » Mon Jul 29, 2019 2:36 pm

Mark

I had thought that you were idling and running well with the exception of high speed...

Intake leaks rarely manifest themselves across both ports and give lean looking plugs on all 4. Usually misfiring will occur, leading to enrichening the mixture which then fouls the "sealed" plugs. That said, if you do believe that you wrestled with the manifolds, you may have "dinged" them...additionally, this is the first I've heard you are running hot. You may indeed be on the correct path...
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Re: Evaluating Spark Plugs

Post by Steve Jelf » Mon Jul 29, 2019 2:43 pm

It doesn't hurt to help the copper crush gaskets with some high-temp RTV, especially if your block has any pitting.
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Re: Evaluating Spark Plugs

Post by Mark Osterman » Mon Jul 29, 2019 3:35 pm

Never had problems before, the block is pretty smooth, but will give it a go this time. A little on the block side of the ring gasket?


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Re: Evaluating Spark Plugs

Post by Mark Osterman » Mon Jul 29, 2019 3:38 pm

Scott .. well the plugs look lean / hot. Before I remove the manifolds I’ll clean the plugs and put it through its paces for an hour using the carb choke adjustment and re evaluate the plugs to see if it makes a difference.


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Re: Evaluating Spark Plugs

Post by Mark Osterman » Mon Jul 29, 2019 10:05 pm

Well ... screwed up. Cleaned the plugs, removed the manifolds and cleaned the ports ... and reassembled the manifolds with new copper ring gaskets and high temp sealer. Went to start the car and had a hell of a time. Not typical. It chuffed a little and the bendix sounded funny. Got it running on number one and two cylinders and thought maybe the gaskets weren’t fully seated so I tightened the manifold nuts and stripped the last one near the back. So, never got it running on all four and am dead in the water.

Am going to visit family in Mass this week and will stop at Langs to get new gaskets and a new manifold stud to try again. I might think about getting a new exhaust manifold too. This old one has been a bear to get installed perfectly and that might be one of the causes of leaks. Not used to not having the T running ... a daily driver. So am having withdrawal symtoms.

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Re: Evaluating Spark Plugs

Post by kmatt » Mon Jul 29, 2019 10:31 pm

Mark; While you are at Langs I would get that new exhaust manifold, yours sounds a little warped at the back.


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Re: Evaluating Spark Plugs

Post by Mark Osterman » Mon Jul 29, 2019 11:24 pm

Yes “manus manum lavat” the exhaust was warped. It prevented me from getting the intake tightened down enough. Who knows, could be the source of the fuel problem of the carburetor. Never had a problem with that manifold before installing the U&J. Engine ran fine. Guess it was just its time.
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Re: Evaluating Spark Plugs

Post by Steve Jelf » Mon Jul 29, 2019 11:40 pm

I believe new exhaust manifolds come only in the 1925-1927 style. If you care about that, you'll need to find a good used one for an earlier car. I consider a manifold toast if it's warped more than ¼". Under ¼" it will probably survive straightening. Some claim that straightening a manifold burns up more gas than the price of a new one, but that has not been my experience.
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Re: Evaluating Spark Plugs

Post by Mark Osterman » Tue Jul 30, 2019 7:35 am

I’ll buy a new one at Lang’s this week. Don’t care if it’s a little different than the original. Will be nice to not have to wrestle with a warped one. If I can find a decent used one at Hershey this year I’ll buy it. What is the diffeencd between the 1923 and 1925 design?

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Re: Evaluating Spark Plugs

Post by Steve Jelf » Tue Jul 30, 2019 8:28 am

IMG_3319 copy.JPG
Top is 1924 and earlier; bottom is 25-27. All the dealers have used parts not listed in their catalogues, so Don may have the right used one for you.
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Re: Evaluating Spark Plugs

Post by John kuehn » Tue Jul 30, 2019 8:40 am

I have one of those borderline manifolds on my 21. Meaning it’s off just enough to not be able to use the rings on it. I’m using the flat style gaskets and no leaks yet but eventually will just buy a new one. The exhaust manifolds that are being made are pretty good and one of the repro T parts that are worth the price. For me anyway.
I still have 3 extra originals that are decent but not straight enough to use with the rings.
The one on my 24 Coupe I straightened and it’s fine. It still had good threads and was a good candidate for straightening.


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Re: Evaluating Spark Plugs

Post by John kuehn » Tue Jul 30, 2019 8:45 am

So is the exhaust manifold something that is crucial in judging for originality at the car shows? I’m not a purist and was wondering about it. After almost a 100 years I wonder how many T’s still have the originals on them.


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Re: Evaluating Spark Plugs

Post by Mark Osterman » Tue Jul 30, 2019 9:32 am

My T is a daily driver with a mostly unrestored body. So I’m not worried about points. Though at some point I would like to find a good used manifold. I do have an NOS heavy ones made in Argentina that I found at Hershey last year for $5.

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