Just for clarity, you gapped the plugs to factory spec. They do not come out of the box with the correct gap.
You might want to read this. https://www.ngksparkplugs.com/about-ngk/faqs/spark-plug-faqs/do-i-need-to-set-the-gap-when-installing-a-new-set-of-plugs
The suggestions previously posted are good advice. Check your ignition wires, cap & rotor, etc. You could even have a sticky valve or the rockers are not set right.
I have a 69 cougar that originally came with a 351W 2 barrel and it never idled right. It was like that before and after the engine was rebuilt. It had no vacuum leaks. It gave me fair performance otherwise but that idle problem drove me crazy. After replacing the whole ignition and carb/intake (stock manifold) with a Holley 600 4 barrel it still idled poorly. The Pertronix breakerless unit worked fine; starting was better than with the points. At one point I had the single exhaust replaced with a dual exhaust; They initially put on some straight thru mufflers which were too loud and the car ran terrible at all speeds. I demanded they put on a set of simple turbo mufflers and the car was back to normal but it still idled crappy. Through all of this my plugs were gapped to .035".
I installed an MSD 6AL ignition amplifier and wow what a difference. I gapped the plugs at .060" and set the timing (normal) and my idle problem went away. I think the problem stems from a poor intake manifold design where 1 or 2 of the cylinders gets a lean charge at idle. The combo of the breakerless ignition and the MSD unit is the hot ticket in my opinion.
So I just installed a new pedapter from RCCI, along with a brand new engine-gauge harness (no resistor wire). The pedapter bypasses the resistor wire in the dash of course, so I thought I’d better run the unit in its 9V mode (I bought the switched one). I have a 1.5 ohm Flamethrower coil (and an original Ignitor I) for the record. Went for a spin around the block and came back home. The engine was still missing at idle and not driving well either.
Pretty frustrated at this point, so I decided to switch over to the 12V coil feed just to see what the hell…
What a DIFFERENCE! Night and day…no more misses at idle. None. Headlights on, brake pedal depressed and idling in drive at 550 rpm for more two minutes; smooth as silk. Went for drive…no more missing and much better performance. The car has never run so well…
There are of course problems with this I understand. First of all, my factory tach does not work in 12V mode. But more importantly, pretty much everyone here (and elsewhere) all say that a straight 12V to the coil will eventually smoke it. So my question is…how do I maintain the great performance I’m getting in 12V mode without regularly cooking the coil? Would installing a 3 ohm coil work? If so, would I have to change the ignition module as well? I feel like I have have finally found the solution to an incredibly maddening problem, but the cure is worse than the symptom.
Anyone…?
When you increase the voltage to the coil, you get an increase in voltage out of the coil. Voltage “pressure” is what causes the spark to jump the gap. The first gap to be jumped is from the rotor to the contacts inside the distributor cap. Check the rotor and make sure it is not burned on the end and is lining up well with the contacts in cap and that the center contact is in good shape. The second gap is the spark plug gap. If you did not set the gap when you pulled the plugs out of the box this is the first thing you should check.
Cap and rotor are new…Plugs are gapped at .035"
New really doesn’t mean much. You can put some modeling clay under the cap and get a mold of the rotor position relative to the cap. It is messy but it works. The gap setting for a stock coil is .032 to .035. You set new plugs to .032 and with wear the gap gets bigger. Out of the box plugs are around .42. Physics tells us that more spark voltage is fixing the problem. The question to be answered is why does it require higher voltage. It would be very tempting to gap the plugs at .030 and see what that does. At least it is free… Hang in there. These mysteries eventually get solved.
I appreciate your time and advice Bill. I will pull the plugs again and regap to .030 just to see…I will advise on the results. BTW, I plan on subscribing to the magazine in the next day or so.
Cheers,
Dennis
Re-gapped the plugs to .030 as suggested above. Made no difference whatsoever…nearing the end of my rope now.
The way you have to look at this is that you are eliminating variables. Now you know that the plug gap is not the issue. I would still set them at .032 while you are working through this. Now it is time to check out the rotor and cap. What does the top of the rotor look like?
You’re right of course Bill. I’m just so frustrated at this point…I’ve been chasing this miss forever it feels like. Pics below…
One end of the rotor is burned off. See how the tip is no longer symetrical? That needs to be replaced.
Yes, I see…well something is going on inside the cap as you alluded to earlier, because that rotor is not even a month old.
Ouch! These new parts are some times not great but that is terrible. Be sure the cap is dropping all the way down on the distributor, all the way around, and the screw is in the little window for alignment.
I have spent some time examining the issue and have concluded that there is indeed an issue with the cap seating. Plan to proceed carefully and with a new premium cap and rotor. Professional consultation is also nearby and available.
Stand by sir…
Update…
Well I am cautiously optimistic that my ignition problem is solved. Whilst re-gapping my plugs back to .032, I took the opportunity to measure the resistance of each plug wire (which I was told by the previous owner were new…), and I discovered a faulty lead on the #8 cylinder. Repaired it with a new terminal and also replaced the (new…?) distributor cap with a premium unit as again, I discovered that the old unit had a seating problem. A new rotor to complement it and…(fingers crossed…) success!
Went for a 70 mph cruise over to the next town and back with noticeably improved performance. Then, with the the engine at its hottest operating temperature, I sat in the garage with the the headlights on, brake pedal depressed, and listened to her purr in drive at 600 rpm with no misfires for over a minute. All this with an RCCI pedapter supplied, OEM coil voltage of 9v.
Cautiously optimistic at this point, as stated earlier, but happier than I have been in a long while. I just wanted to say thank you to everyone (especially Bill from Legendary Cougar Magazine) for your selfless time, advice, and patience with a novice such as myself. I just hope that I can pass it along, as it has been done for me.
Cheers everyone!
Dennis
WOO HOO! That’s great news Dennis! I think you nailed it. Here is the really great part of this. In the future, people will read this thread and the light bulb will go on and they will be able to solve the problem in no time at all. All because you had to work through it the first time. Now go put some miles on that Cougar.
Thank you Bill…all the best!
That’s a really nice looking cat. I love the blue with white top. Just plain sexy to me.
Like Bill said, go put some miles on her.
Thanks Daryl…I’m really happy to be part of such a great community. Cheers!
