100-6 has a miss when accdelerating

[longbridgehealey]

Hi everybody. My 100-6 has a miss when it's accelerating in third or fourth gear, usually at lower rpms. It started last week, and is getting worse. It starts up fine, and has no problem (yet) in first or second, but it does seem a little sluggish. It has a new petronix ignition in it, but older plugs, wires and cap. It has a new red rotor from Jeff. I'm pretty ignorant about these things, what should I do?

Thanks,
Larry

 

[Healeysince59]

I'd try new plugs first.

Marv J

 

[longbridgehealey]

Yep, I was thinking of replacing the plugs, wires and maybe the cap?

 

[JPSmit]

note the colour of the plugs, you may be running too rich - black and sooty is too
rich

 

[Bob_Spidell]

I had the same problem in my BJ8. My money's on the cap or secondary ignition wires. If you're using a stock cap--with screw terminals--you need to use stranded copper wires (7mm). Modern suppressor wires don't work well or for long with the standard cap.

Also, watch your engine running in a dark, but ventilated garage and look for arcing on the cap. I've not had much luck with aftermarket caps--usually, they're Bosch brand--but Lucas caps work well (expensive, but should last the life of your car unless it's a daily driver).

 

[longbridgehealey]

Thanks everybody. New wires, plugs and cap on the way from Inan at Healey Surgeons. Jeff at Advanced Distributors said to set the plugs at 32/1000. He also said that the Petronix ignition isn't ideal for the 100-6. Not great news at this point.

Larry

 

[bob hughes]

Make sure that your replacement plugs are the hot ones, found out the hard way on that score after being advised of a certain type, failed one by one because they were the cold ones

 

[Keoke]

Jeff at Advanced Distributors said to set the plugs at 32/1000. He also said that the Petronix ignition isn't ideal for the 100-6. Not great news at this point.

Well I kiny disagree, since you have more spark whether you are running a stock coil or an uprated one the plug gap with the pertronix can be opened up we run about 0.040 thou most of the time with a Lucas sport coil but you can try say 0.036 thou first and see how she goes.--Fwiw-Keoke--

 

[57_BN4]

Interested to know the 'why' of why the pertronix isn't ideal for the Healey engine. I have Pertronix'd every engine for the last few years and I think it is one of the best improvements on any older engine. I always carry a small zip-top bag with the original points and a small screwdriver just-in-case...

The only improvement on the Ignitor would be if they produced an Ignitor II to fit the 22/25D distributors as these have true dwell control. I did bodger a Toyota one into a 25D dissy once but it isn't a nice fit as the sensor is quite a bit taller. Much more spark from the Ignitor II = 1.1mm gaps.

 

[longbridgehealey]

Thanks Keoke, will do.

 

[longbridgehealey]

He didn't really say why. I've got petronix on the 100-6 and the 67 sprite, haven't had any problems yet - except for this, which hasn't been linked to the petronix yet....

 

[longbridgehealey]

Here's the update, and some new questions. Put in the new cap, new red rotor, wires and plugs. Like Keoke said, gapped them at .036. She is running great, took her out forabout 40 miles.

The second and third plugs were black, and the red rotor (which was one month old)had some black in the center. So I replaced the rotor too. When the Petronix was installed last month I put the red rotor in, and she ran great for a couple of weeks, then the troubles started. The wires were not replaced back then, and the spark plug gap was not adjusted.

So my question is: Do you folks think I've corrected it, or just temporarily covered up the problem?? :confuse:

Thanks,
Larry

 

[nevets]

If I understand you correctly, the car is running great. I say enjoy it while it lasts!

 

[longbridgehealey]

Yeah, sometimes I tend to over think things!

Thanks,
Larry

 

[bighealeysource]

Hey Larry and Keoke,
Been reading this and find the gap suggested interesting. I have a 6 port head
on my 58 BN6 versus Larry's engine. Also using the Petronix, should I set the
gap at .036 as Keoke recommended for the same reasons ? Currently gapped per the factory recommendation.
Thanks,
Mike

 

[longbridgehealey]

Hi Mike - I don't think Keoke's seen your post yet, or he would have answered. I don't know the answer, all I can tell you is my 100-6 is running very strong, and the miss is gone. Keoke actually suggested .040 at first, I'm thinking of giving that a try. (or maybe I should let well enough alone)

Larry

 

[57_BN4]

Although I have never experienced it myself, I can understand the logic behind Pertronix recommending to replace the coil with one of theirs when fitting the ignitor. A coil that has many heat cycles and hours of vibration on it will have areas in the windings that are less robust than they once were.

Adding an electronic points improves how quickly the coil current is interrupted and opening up the plug gaps increases the peak firing voltage. Both these factors stress the coil far more than originally and those weaker areas in the coil windings can short internally and quit without warning

My rather limited experience of playing with plug gaps is that 0.040 is bigger than the standard coil (Zephyr/Lucas) can cope with. Biggest effect is how well the engine accelerates away from idle when cold as the hardest mixture to fire is lean/cold. More choke needed to avoid hiccuping = gaps too big, all else being equal. I settled on 0.036 although I reckon 0.040 would work with a better coil.

Andy.