Is it possible for a coil on a points ignition with external ballast resistor to weaken after sitting for 20 years ? I replaced plugs,wires,cap,rotor , points and condenser. After it warms up it will occasionally start missing. Coil is mounted horizontally up under the dash. I dont think it should be mounted that way. Can a weak coil cause a miss ? Dont know what the specs are on the coil to even test it. I think the engine is close to stock any suggestions on a replacement coil ? NAPA ?
Excessive heat and vibration are the normal killers of a coil. So as long as the coil wasn't stored in a vibrating, 750° furnace, it "should" be fine. "Should" being the key word...ANYTHING is possible. Mike
More likely the new offshore POS condenser is the culprit. If running points & condenser they must be made of good stuff.
Odds are the replacement parts may be the problem. I have found the only ignition contacts and condensor to be used are NAPA Echlin heavy duty. Assumiing its a chevy it would use CS786 contacts and RR175 condensor from NAPA...... The new "jap/china condensors are really poor quality nowdays.......
Gmc bubba , i did replace the points and condenser with the numbers you listed from NAPA. So far all parts have come from NAPA. I was thinking for the price of a coil I would change it. Hate replacing parts and nothing improves
It's common for an iffy coil to work cold and cut out after heating up. Most in my personal experience cut out completely until they cool off, but anything is possible. Sent from my LG-TP450 using The H.A.M.B. mobile app
Some coils don't seem to like being mounted horizontally. They'll work, but they're possibly not sealed well enough and can slowly leak oil. Free and easy test? Mount it vertically and get it out from under the dash where it can get some air circulation around it. Like on the firewall or a bracket mounted to the intake manifold. You mentioned having an external ballast resistor. Does the coil actually require it? Have you checked the voltage at the coil during cranking and running conditions? If you need a refresher course on conventional points type ignition systems, you might give this a read-thru... https://www.jalopyjournal.com/forum/threads/hot-rod-technical-library-basic-ignition-systems.983424/
Claymart, i do need a refresher its been many years since i had a points ignition. I picked up a coil at NAPA. Huge difference ! Now you can hear the spark snap on a grounded plug. Running pretty well right now. Still a little lazy on a steep hill around 2000 rpm. Car sat 20 years so little by little it’s getting better.
And it's got a picture of "Big Daddy" on page 3, so you know it's got to be good information! With the old coil, did you ever notice its operating temperature? They'll get warm, or hot even, but they shouldn't be so hot that you can't at least touch them momentarily. As also noted in the link above, the ballast resistor will build a lot of heat as well. If it's under the dash too, you might consider also mounting it somewhere else with some more air circulation.
Coil wasnt too hot , ballast is mounted on an aluminum heat sink. Its a lot better with new coil but is missing around 2000 rpm even if its in park. Not sure if its ignition or a fuel issue. Carb is a 1406 edelbrock and was just rebuilt. Plugs on the right bank are a lot lighter tan than the odd bank. But theres only 100 miles on em. Maybe plugs are crap too i never have luck with AC plugs
When I went to BMW school in Culver City years ago, the NGK spark plug Research/Distributing center was next door... I spent some time with the rep, made me an NGK user from then on. GREAT PRODUCT, I use them still. (SBC, BBC, SBF, FE, and my Hemis. Last long.)
Thoughts.....check the dist. shaft for play. Grab the top of the shaft and see if there is any side to side movement. If there is, the points gap setting will be all over the place and could cause a miss.
Funny you should mention NGK. A few years ago I tuned up my Moto Guzzi, points, condenser, and plugs. It started but only on one cylinder. Swapped in old points, then condenser, then old plugs. The old plugs fixed it. Put all the new stuff back and it ran on one cylinder. By holding the plug wires away and making the spark jump it ran on two. Swapped back the old plugs and it's been good ever since. The new plugs were the correct number NGK's. I had never had trouble with them before but haven't used them since.
I did check the distributor and there is no play side to side. I plan on changing the distributor this winter after cruisin season. It’s actually stuck and i cant move it
You mentioned the miss occurring after the engine warms up. Does the carb have a choke, is it adjusted properly and is it fully opened at normal operating temperature? How much manifold vacuum are you making at idle and at a steady cruising speed? Is the vacuum steady? Seeing as how the car was stored for quite a few years you might double check that the power pistons and metering rods are moving freely in their bores, even though the carb has been rebuilt. Make sure the metering rod tips aren't bent while you're at it.
Not sure on the vacuum i need to buy or borrow a vacuum gauge. The metering rods appear to be ok. Does one side of the carb feed one bank ? I never understood how the fuel runners work. Offenhauser dual plane
It looks like the right bank is running lean, left bank ok according to the plugs. Maybe it just needs to be driven more or should i put some snake oil in the gas ?
I also found the owners book for the 1406 edelbrock carb it calls for 1-1/4 “ float drop and the carb kit called for about 15/16 “ drop. Not sure what to set it at.
I took the carb off today the choke was stuck almost 3/4 !! Took care of that i think, havent run it yet but noticed the metering rods are really rough on the bottom. Ordered rods and jets. Hopefully it’ll take care of it. Good call claymart.
Generally, dual-plane intakes are better suited to mostly stock, street driven vehicles. Each side of the carb supplies four cylinders, though it's split up as two cylinders on each bank per side. The float "drop" spec isn't nearly as critical as the float "level". Float level will affect the fuel mixture to some degree. Either of the float drop specs you've seen will probably work OK and have no real effect on driveability. Are you saying that the choke valve was sticking 3/4 of the way closed? That would make things plenty fat after the engine warms up. If you don't want to mess with fixing the choke for right now you should be able to find a way to wire the choke valve in the fully vertical, open position. It may make it a little harder to start cold but it should run and drive a lot better when warmed up. Do you mean the tips of the metering rods were really rough or did you mean the power pistons? Usually the only bad thing that happens to the metering rods is the tips being bent from somebody getting "ham-fisted" when installing them. They won't tolerate a forceful installation. They should only be installed AFTER the airhorn is installed on the float bowl. It may take a couple tries with lightly tapping the power pistons with finger pressure only, but eventually the rod tip will drop into the center of the jet. And don't forget to put the springs back under the power pistons or you'll get to do it all over again.
Choke was stuck about 3/4 open. Got that fixed works fine now. Calle edelbrock tech set float level 7/16 and float drop 15/16. Yeah the metering rods were messed up at the bottom end and i think your right someone moosed the air horn on and scuffed them up. Power pistons appear to move freely. Hopefully it will run better when the parts come.
I think the oil in a coil is there to cool the coil internals. Mounting it on it's side removes some of the internals from the oil. I read this somewhere years ago and wish I could find it to lend some credibility to my post.
Either that or the oil helped make all the pluses and minuses run around smoother and faster in there. Strangely, I remember picking up and shaking coils and sometimes you could hear the oil sloshing around a bit and other times they sounded either completely empty or completely full. And you seldom saw any obvious sign that they'd been leaking. Some were designed to be mounted upside-down or on their side and were apparently sealed well enough to allow it. But I always figured if you could hear oil moving around in there it was probably best to mount them with the "business end" up. Either way it would seem best to mount them where there's a bit of air circulation.
I read somewhere, oil filled coils when mounted horizontally must be oriented with the terminals at the 3 and 9 o'clock position, to keep the innards properly bathed in cooling oil.
I seem to remember reading the same thing. The positioning as such ensures both coil posts are submerged in the oil for thermal cooling purposes. Thank you for chiming in and reassuring me my dementia isn't that far along yet.
Has anyone seen cylinders 3,5,4,6 appear to run lean ? Pulled plugs those 4 are very light colored compared to the rest.
Sounds like an intake problem,, maybe gasket. Can you check it by spraying carb cleaner while it idles. If it changes RPM you found a problem.
Well it turns out it was starving for fuel. I went 1 step rich on the metering rods and and no more stumbling and lack of power in the 1500 to 2000 rpm range. Now i need to get the distributor loose so i can advance timing a little. So far it ain’t cooperating.
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