1953 Mercury unusual plug condition

[Merc Cruzer]

This question is about my 53' Mercury with a stock flathead engine, and the original stock distributor, along with the original stock Holley 1901 Teapot carb.

Plugs 1,4,5,8, are burning normally and clean, but plugs 2,3,6,7 are burning rich and black. To restate: the 4 corner plugs are burning normally and the 4 center plugs are burning rich.

Has anyone run into this situation? If so, what was the cause?

As a side note, the car runs fine.

Thank you,

Roy

[petehoovie]

Originally Posted by Merc Cruzer

This question is about my 53' Mercury with a stock flathead engine, and the original stock distributor, along with the original stock Holley 1901 Teapot carb.

Plugs 1,4,5,8, are burning normally and clean, but plugs 2,3,6,7 are burning rich and black. To restate: the 4 corner plugs are burning normally and the 4 center plugs are burning rich.

Has anyone run into this situation? If so, what was the cause?

As a side note, the car runs fine.

Thank you,

Roy

[Bill OH]

I would find a diagram of the runners of the intake manifold and I am of the opinion that one of barrels of the carb is feeding too much fuel. I would take a look at the main jets for size - do not think it is float level or defective power valve. - float level and power valve affect both barrels. Take a look.

[aussie merc]

im with Bill loose jet or blocked emulsion tube

[Merc Cruzer]

Sounds like a good place to start.

Thank you,

Roy

[tubman]

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"If it ain't broke, don't fix it". If the black plugs become a problem, replace them with plugs that are a heat range or two hotter.

[38 coupe]

This sounds odd to me. If one side of the carburetor was running rich you would have sooty spark plugs on two outside cylinders on one side of the motor and the two center cylinders on the other side of the motor. All inside cylinders rich is both barrels of the carburetor.

[ford38v8]

Originally Posted by 38 coupe

This sounds odd to me. If one side of the carburetor was running rich you would have sooty spark plugs on two outside cylinders on one side of the motor and the two center cylinders on the other side of the motor. All inside cylinders rich is both barrels of the carburetor.

Good call.

[rjlester]

I wonder if the exhaust crossover is plugged?

[Ross F-1]

Interesting that those are the 1st four cylinders in the firing order; could the cap be off-center?

[Merc Cruzer]

Originally Posted by rjlester

I wonder if the exhaust crossover is plugged?

I have duel exhausts, with the correct factory manifold, on the the drivers side.

[Merc Cruzer]

Originally Posted by Ross F-1

Interesting that those are the 1st four cylinders in the firing order; could the cap be off-center?

I checked and it is correct.

[38 coupe]

I like Ross's suggestion of ignition as the source. Have you checked the distributor for bushing wear or off center point cam? I ran into each of these problems on different distributors and had a heck of a time diagnosing the problem.

[Merc Cruzer]

Originally Posted by 38 coupe

I like Ross's suggestion of ignition as the source. Have you checked the distributor for bushing wear or off center point cam? I ran into each of these problems on different distributors and had a heck of a time diagnosing the problem.

I put new bushings in the distributor a few months ago, just prior to having it set up on a Sun distributor machine.

[Als48]

I worked on a tractor once, that had a distributor problem which sounds like this issue. It was running but only on two cylinders. I found the cap to be distorted or warped and was able to correct it by filing the portion that had to fit into the ID of the distributor more round. That allowed the cap to center up properly and the plugs to fire more evenly. The cap must have been canted slightly, causing the rotor to miss firing two of the cylinders. I scratched my head over that one for a day or two.

Al Hook

[Merc Cruzer]

I cleaned the plugs this morning and took it out for a lengthy drive. I had changed the timing a coupe of days ago and wanted to see if the new timing resulted in additional power. Bottom line, it did. Previously I had done a series of short drives, involving steep hills to see if the new timing resulted in additional power. I am beginning to think the short bursts of acceleration, allowed the power valve to open, dumping additional amounts of gas into the the intake, yet not burning completely in the center 4 cylinders.

I live at 8300 ft and currently running 54's, for the two main jets. I will take the carb off later this week, to go through it and will change the jets to 52's, as that will serve to further clean up the plugs. The 4 corner plugs are good, but could be better anyway.

Thank you all for your suggestions and input.

[ford38v8]

Originally Posted by Merc Cruzer

…I live at 8300 ft and currently running 54's, for the two main jets. I will take the carb off later this week, to go through it and will change the jets to 52's, as that will serve to further clean up the plugs. The 4 corner plugs are good, but could be better anyway.

Thank you all for your suggestions and input.

Merc, at 8300 ft, less oxygen should translate to less fuel. Using .054s for jets does the opposite. Ford’s sea level jets were .050, no wonder your plugs are sooty.

[Bored&Stroked]

Given you're talking about plugs, coloring, etc.. How are you actually checking them? You can't just drive it, hit some stops on the way back and pull the plugs in the garage - that will tell you nothing. You have to load test on the highway, push the clutch in and coast to a stop. Also, reading plug colors with today's fuel is difficult. I don't see "chocolate" colors anymore. So, I use an O2/AFR meter to actually tell me what is going on.

[Merc Cruzer]

ford38V8 and Bored&Stroked,

The speck for 53' Merc is Sea level = .056 and 5,000 to 10,000 = .054. Since I am currently running .054 and it is still a bit on the darker side, I will give the .052's a shot. If that turns out to be too lean, then I will go back up to .053's. Lucky I have a nice collection.

Normally what I do, is take it out for a 30 mile drive on the highway. That allows the car to run at speed for a period of time and the return trip involved allot of uphill driving, with the engine under load. We are talking about climbing 3000 feet in 13 miles. At the end of the trip I pull the plugs to inspect them for color and fowling. Unfortunately, it is the best I can do.

Now as to your suggestion of: "You have to load test on the highway, push the clutch in and coast to a stop.", the closest would be shift it into neutral and come to a stop. I have a Merc-O Matic. The 02/AFR meter would be a great thing to have but, the cost is a bit prohibitive and I don't know anyone that currently has one. So unfortunately I will have to give it my best shot.

Thank you both for your input and suggestions, I appreciate your advice.

[ford38v8]

Merc, my mistake. I'm stuck in the .94 mode of thinking, not the Teapot. Your .054 jet size does make sense now. I hate to have unanswered questions, but Tubman's suggestion might be the way to go. Still, with the high altitude, that in itself may account for less vacuum on the longer runs, dumping a higher volume of fuel in the near cylinders. I don't know what I'm talking about, just a stab in the dark.

[Merc Cruzer]

Originally Posted by ford38v8

Merc, my mistake. I'm stuck in the .94 mode of thinking, not the Teapot. Your .054 jet size does make sense now. I hate to have unanswered questions, but Tubman's suggestion might be the way to go. Still, with the high altitude, that in itself may account for less vacuum on the longer runs, dumping a higher volume of fuel in the near cylinders. I don't know what I'm talking about, just a stab in the dark.

ford38V8,

You are right as to the vacuum, I can only generate 12-13 on a good day, no matter what I due to tune for higher vacuum.

Tubman's suggestion, is a good one and at this point, I am thinking just a thorough cleaning and swapping out the jets for .052's and looking for a with a lower vacuum requirement (if there is such a thing, my current one is a 52). This is what happens when you start going for just a little more performance.

Thanks again,

Roy (Meerc Cruzer)

[Merc Cruzer]

Originally Posted by Bored&Stroked

Given you're talking about plugs, coloring, etc.. How are you actually checking them? You can't just drive it, hit some stops on the way back and pull the plugs in the garage - that will tell you nothing. You have to load test on the highway, push the clutch in and coast to a stop. Also, reading plug colors with today's fuel is difficult. I don't see "chocolate" colors anymore. So, I use an O2/AFR meter to actually tell me what is going on.

Just curious, when you say reading plug colors with today's fuel is difficult, why?

[Bored&Stroked]

Originally Posted by Merc Cruzer

Just curious, when you say reading plug colors with today's fuel is difficult, why?

Today's fuels are so over-refined, that I find it difficult to obtain the ole chocolate colors we used to rely on.

I tend to see the insulator looking much more white - which in the old days would tell me too lean. I've seen the same thing at the race-track . . . plugs tend to look "hot" when they are not.

I also pay a lot of attention to the plating on the electrode and the bottom of the plug. I tend to use NGK plugs only - as the insulator and plating tend to tell me a lot (especially with heavy load conditions).

This is one of the reasons I like an O2/AFR meter - so I actually know what is going on - versus guesssing. They are not that expensive - and are a great tuning tool.

[tubman]

Dale, I am having a hard time seeing how an O2/AFR meter would help to find the problem here. If you didn't have 2 of them, you would be reading the AFR of the entire engine. (With two, you would at least be able to read each bank.) How would you be able to narrow it down to an individual cylinder (or cylinders)? Don't get me wrong; I'm a fan of AFR meters and have on on my run stand, but I fail to see how it would help to track down what appears to me to be a fuel distribution or ignition problem.

[Merc Cruzer]

As it turns out, there is a smaller power valve, and I happen to have one:


Roy,

The brass power valve marked #52 has two .037" holes in the shank of it to increase the enrichment when undel a medium to heavy load. The one marked 28 has only one hole that is .028" and was used on the '56 Ford/Merc 292 and 312 Y Block 4 barrel teapot carb. '55 teapot four barrels used a #43 power valve which had one .043" hole.

Most power valves in other carbs only had one hole as small as .021" in some carbs.
If your feel you're too rich because of the high altitude, changing the main jets to a smaller size will make it leaner under light, medium and heavy load.

The Holley manual says two sizes smaller for 5,000 to 10,000 foot altitude.

Sal

[Ross F-1]

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Originally Posted by tubman

Dale, I am having a hard time seeing how an O2/AFR meter would help to find the problem here. If you didn't have 2 of them, you would be reading the AFR of the entire engine. (With two, you would at least be able to read each bank.) How would you be able to narrow it down to an individual cylinder (or cylinders)? Don't get me wrong; I'm a fan of AFR meters and have on on my run stand, but I fail to see how it would help to track down what appears to me to be a fuel distribution or ignition problem.

Given the way the intake manifold is made, reading an O2 sensor on one bank is really reading 2 cylinders from one side of the carb and 2 cylinders from the other. Putting 2 O2 sensors really doesn't buy much more information.

[Merc Cruzer]

I also switched the pump arm, to the least amount of gas (far left). It was set on the highest ( far right). Admittedly it is a minor adjustment, but I am trying to be systematic in the process. Now need to do a few test runs.

Next I will switch out the power jet to the .021.

If that is not enough, I will go with smaller main jets, either: .053's or .052's

[tubman]

Originally Posted by Ross F-1

Given the way the intake manifold is made, reading an O2 sensor on one bank is really reading 2 cylinders from one side of the carb and 2 cylinders from the other. Putting 2 O2 sensors really doesn't buy much more information.

All I'm saying is that two meters would narrow down the problem to one set of four cylinders rather than all eight if they had different readings. I don't think it would matter much to me whether the four cylinders were in the same bank or not.

My original question still stands.

[Merc Cruzer]

Sorry for taking so long, but being retired doesn't mean you have an empty schedule.

For now I am going to live with this. I probably could go down a jet size though. It is a little trickier at 8300 ft.

Thanks again, for all of your suggestions.

[tubman]

I know people who would die for a set of plugs that looked like that.

[petehoovie]

Originally Posted by Merc Cruzer

Sorry for taking so long, but being retired doesn't mean you have an empty schedule.

For now I am going to live with this. I probably could go down a jet size though. It is a little trickier at 8300 ft.

Thanks again, for all of your suggestions.

[Merc Cruzer]

Originally Posted by tubman

I know people who would die for a set of plugs that looked like that.

Thanks, I am happy with my efforts so far. It makes her more fun to drive, now that I have resolved a few of smaller issues. She runs smoother now, than she ever has. Rather than mentally complaining about any minor hesitations of late reactions to acceleration, I now notice the condition of the road, I driving on. I think I will turn on the radio and enjoy a few songs from the 50's, the next time I take her out.

[Lawson Cox]

Originally Posted by ford38v8

Merc, my mistake. I'm stuck in the .94 mode of thinking, not the Teapot. Your .054 jet size does make sense now. I hate to have unanswered questions, but Tubman's suggestion might be the way to go. Still, with the high altitude, that in itself may account for less vacuum on the longer runs, dumping a higher volume of fuel in the near cylinders. I don't know what I'm talking about, just a stab in the dark.

Alan: So your commens are merely a WAG (Wild Ass Guess) then? Then again, with your knowledge and experience, I will elevate that to a SWAG. (Scientific, wild ass guess.)