spark plug questions

[Carolina Tee Bird]

One mechanic changed the spark plugs in my 60 Bird which has a mid 60's 390 motor to Motorcraft BSF 42C. Not sure what was in there before. After about 2,000 miles I took the car to an old Ford mechanic (different guy) for carb and timing adjustments. He noted "plugs were dirty but carbon should burn off since adjustments". I checked the plug condition after about 3,000 miles and they are black with carbon and suit. Wondering if the choice in plugs was the right one and should they have been changed again? Can't find spark plug recommendations on the site. Engine seems to run better since carb and timing adjustments but still idle is a little eratic when engine is hot. Running BP 93 octane plus octane boost. Ignition was upgraded to electronic. Thanks guys for responding.

[simplyconnected]

Black soot usually means your mixture is too rich. Your carb's idle adjustment is probably off as evidenced by the soot and the fact that the engine runs erratic at idle.

Octane means very little at idle speeds. Octane plays a part when the engine is under a load and only if you experience ping and knock.

Are you confusing octane booster for lead additive? Pump gas already has enough octane.

I have to ask, is your engine burning any oil? - Dave

[Carolina Tee Bird]

Great to know about octane boost. I was not using a lead additive. The motor was rebuilt about 5,000 miles ago (but 8 years ago).I bought the car from the owner that paid to restore it but then put it in storage for 7 years. Do you recommend a lead additive? Any paricular brand? I am hoping last mechanic adjusted carb and timing properly and judging by what the plugs look like, I believe they need to be changed. The plugs were dirty before the adjustments and the carbon has not burned off as mechanic suggested it would. I don't believe the car is burning any oil, no smoking etc. At this point, oil has about 2,500 miles on it and looks like it's due to be changed ( now looking brown) which will happen soon. Thanks for responding.

[jopizz]

Do you recommend a lead additive? Any paricular brand?

There aren't that many choices. Gunk makes a lead additive that I've used and is available at most auto stores. Unless you have hardened valve seats I would recommend using it just to be on the safe side.

John

[Carolina Tee Bird]

Thanks John, any recommendations regarding the plugs? The 390 was bored with a slightly larger cam.

[simplyconnected]

John raises an excellent point. Do you know if your exhaust valve seats were machined with hardened seats installed? If so, you won't need lead. - Dave

[scumdog]

Valve Seats

For those that are concerned or maybe just curious:

I have never had hardened valve seats fitted to any of my motors,
The 1971 429 in my '55 F100 has been in the truck for almost 40 years, I'm not sure the total mileage on the motor but the F100 speedo indicates I have doe no less than 150,000miles.
The T-bird has only been in my possession for 12 years and hasn't done a lot of mikes
I have not had valve recession in either car or any other except for the 1962 Anglia my wife had.
My theory is that unless you are towing a trailer a lot or hammering a motor constantly it will take a long time for valve recession to show.

The Anglia was a classic example: 4:11 rear end gears and running 13" diameter rims meant it was always revvin hard.

Disclaimer: "Your results may vary"!

[simplyconnected]

...I have never had hardened valve seats fitted to any of my motors,..
...I have not had valve recession in either car or any other except for the 1962 Anglia my wife had...

Ok, I can see high rpms but not all the time, Tom. If she's bopin' around town, that 4:11 would make city driving easy on the engine with a 4-speed stick. It's NOT under a huge load. Besides, this engine is very low performance and dirt low 7.5:1 compression ratio. It only produced 39-hp on its best days.

So, what's the answer? Why would the exhaust valves weld themselves to the seats? Emissions. Rpms have little to do with it. They ran this engine hot and lean for fuel economy, a more complete burn and better emissions. Lead in the fuel helped lubricate and cool the exhaust valves. Back then, gasoline had so much lead, it left deposits on the valves. Sustained high rpms would 'blow out' the deposits which helped the engine run better, like after a long trip.

As soon as gasohol hit, I had hardened seats installed in my 1980 Harley. It's an air cooled, low rpm engine but very susceptible to receding valves. Your 4-cylinder Anglia had 60 cubic inches but my Harley had 80 cubic inches in just two cylinders. It does take a while for the valves to recede. It's slow and steady. - Dave

[Yadkin]

One mechanic changed the spark plugs in my 60 Bird which has a mid 60's 390 motor to Motorcraft BSF 42C. Not sure what was in there before. After about 2,000 miles I took the car to an old Ford mechanic (different guy) for carb and timing adjustments. He noted "plugs were dirty but carbon should burn off since adjustments". I checked the plug condition after about 3,000 miles and they are black with carbon and suit. Wondering if the choice in plugs was the right one and should they have been changed again? Can't find spark plug recommendations on the site. Engine seems to run better since carb and timing adjustments but still idle is a little eratic when engine is hot. Running BP 93 octane plus octane boost. Ignition was upgraded to electronic. Thanks guys for responding.

Normally soot on plugs is caused by too rich a fuel mixture. Setting idle screws won't fix this, since that only changes the mixture at idle. Most of the time, fuel is metered by the jets inside the carburetor.

Old school mechanics can smell unburnt gas, then reduce jet size in the carburetor trial and error. However these days most shops should have an O2 sensor to enable the mechanic a better estimate of the best jet size.

[DKheld]

I'm using the Autolite AP45 plug in mine. Similar engine - rebuilt years ago but only around 10K on it now. Probably a stock cam though and believe it was .020 over pistons.

Unfortunately I never had any luck with any copper core plug - Champion being the worst. Think the MOT BSF 42C are the copper core. Always had high revving British cars and the copper core plugs just couldn't take the heat. Switched to Bosch in my British cars and never had any more problems. So far the Autolite 45's seem to be working well in my Tbird. Motorcraft does make a Platinum core plug if you are stuck on that brand.

The OEM Ford 4100 carb on mine was similar at an idle with any octane fuel and my new Holley is a little better but not much. Do you know which carb is on your car? I believe it's the ethanol boiling in the carb at hot idle. Find a station with non-ethanol fuel and see if the problem goes away or at least gets a little better. Non-ethanol fuel will probably be $1.50 more per gallon so go by the bank and get a loan first. (not the high octane racing gas just non-ethanol fuel).

The experts will have to confirm but IIRC the higher the octane the harder the fuel is to ignite. So with high octane fuel and octane additive that might be part of the problem? Of course that may be negated if the electronic ignition system you have has a high output spark.

Just some ideas...

Eric

[Carolina Tee Bird]

Can't tell you any more about the engine other than it was rebuilt by a professional shop around 8-10 or so years ago. Unleaded fuel was certainly used then but can't tell you if modifications were done to accommodate the fuel change.Today, there is 10% or more of ethanol added. The very few gas stations that still offer a leaded fuel show 87 octane. I would rather add a lead additive rather than search for gas stations with leaded fuel (if that's what's recommended) as I drive this car on short trips; not just around town. As mentioned before, engine seems to run OK with exception of erratic idle when very hot. The fouled plugs were dirty prior to the tuning, so not easy to say if the plugs continue to collect carbon. Still think a plug change is in order before further tuning.Checking new plugs after 2,000 miles would indicate further problems. Soooo back to what kind of plugs would you put in this engine? Thanks

[jopizz]

I would stick with the stock heat range plugs for now. I've never gotten hung up too much on brands. To me any name brand plug should be good for at least 50,000 miles on an engine that doesn't have any serious issues. Assuming that your carb and timing have been properly adjusted I would give it at least 1500 miles before I would consider going to a hotter or cooler plug.

John

[Yadkin]

...engine seems to run OK with exception of erratic idle when very hot....

If it's overheating that's a whole other issue.

[newyear]

The shop manual for a 352 ci engine states Champion No F-11-Y
I use NGK APR 6 FS

[Carolina Tee Bird]

Thanks all.....
John: Is the Motorcraft BSF 42C a stock plug that would be appropriate?