Spark plug wires affecting tachometer?

[AUSMHLY]

64BJ8. Negative ground. Pertronix Ignitor Electronic Ignition. Lucas sports coil. Tachometer was sent to Nisonger two weeks ago.

After installing my mechanic says the tachometer does not read correctly. Example, the tach reads 3000 rmp, his equipment says it should be reading 3500.

Nisonger confirmed the tachometer is correct and recommends I replace the stranded copper spark plug wire to suppression wires. Mechanic says performance may not be as good if I replace the copper to suppression.

The car does run great and I have my mechanic to thank for that.

I'd like the tachometer to read correctly and I'm wondering if this situation is caused by using copper spark plug wires, or if replacing them with suppression will solve the problem of the misreading tachometer, and not affect performance.

Anyone using the same set up as me and having the same misreading tachometer?

Anyone using the Pertronix 7mm suppression spark plug wires in this set up, or another brand of wires? If so, does your tachometer read correctly?

Cheers,
Roger

 

[Randy Forbes]

I doubt you'll lose any performance with a good suppression lead.

My MSD6ALII specifically warns against using solid core (stranded copper) leads.

I bought a generic (Mallory or Accell?) V8 set and had plenty of length to get them to fit/look right. I have plug-in terminals at the distributor (Mallory dual point) so using a GOOD crimper was a must__fortunately, I already had a full-cycle ratchet type with the sparkplug lead set of dies. If you're using a side entry cap, you will be limited on insulation diameter. If your distributor has push on terminals, you can use the 8mm lead sets.

Remember: 1 5 3 6 2 4 :wink:

 

[AUSMHLY]

Hi Randy,

I do have the side entry style cap that accepts only the 7mm wires.

 

[Ed_K]

Hi Roger,

Magnecor makes a black set of 7mm wires that will go into the
standard distributor cap.
They are Magnecor part # 6758 .

I have been using a RED set of their wires for several years and
they completely got rid of all the electrical noise in my car's music system. Before I got these wires, I was using solid metal stranded wires and they caused a lot of noise in my car's music system.
If your tach is really being affected by the ignition noise, then the Magencor wires will correct the problem.

https://www.magnecor.com/magnecor1/main.htm

Ed

 

[Ed_K]

Roger,

Have you tried making another loop in the white wire where it fastens to the back of the tach ? If you have 2 loops now, put another loop in it under the clamp. That will transfer more electrical energy into the tach pickup and may cause the tach to register higher for a given RPM. It is worth a try if not tried already.

Ed

 

[Keoke]

Have you tried making another loop in the white wire where it fastens to the back of the tach ?



If you have 2 loops now, put another loop in it under the clamp.

Additionally, make sure you are using a long reach Suppressor type plug. If the radiation from the ignition wires affected the Pertronix you would get misfires. Yes I use the same set up and have for years no problem.

OH!!!!, and the radiation should also make a racket in your radio system.--Fwiw--Keoke-

 

[RAC68]

Hi AUSMHLY,

I too have a 64BJ8P1 and have, for many many years, used copper wires. Four years ago I installed Magnecore premium suppression wires and have found no reduction in performance. It is not uncommon for me to shift at around 5K and have not experienced a miss with the Magnecore 7mm wires or any alterations in tachometer readings from the copper.

About 10 years ago I replaced a failed capacitor that caused my tachometer to read high. In the process, I drilled a hole in the back of the case to access the read adjustment pot and, with the aid of a separate tachometer/dwell meter, set my reading. The hole is now covered by a piece of tape to eliminate any dust intrusion.

If your rebuilt tachometer was set properly set when repaired, I would suggest you also investigate and experiment with the number of wire loops through the pulse sensor (white wire through the plastic piece on the back of the tachometer). I believe Pertronix has a recommendation to address this issue.

All the best,
Ray (64BJ8P1)

 

[AUSMHLY]

Roger, Have you tried making another loop in the white wire where it fastens to the back of the tach ? If you have 2 loops now, put another loop in it under the clamp. That will transfer more electrical energy into the tach pickup and may cause the tach to register higher for a given RPM. It is worth a try if not tried already.
Ed

A couple years ago, when I converted my car to negative ground, I sent my tachometer to Palo Alto Speedometer. They converted it to negative. When I got it back, it did not have the white wire loop set up anymore. I believe they installed a pc board, removed the white loop system and added a spade terminal in its place. I ran a wire from that new spade terminal to the distributor side of the terminal, as directed by both Palo Alto Speedometer and Nisonger.

Over these two years I think the tachometer has not been reading correctly, so two weeks ago I sent it to Nisonger. They bench tested it on a negative Pertronix system and said that the tachometer is reading correctly and sent it back to me. Nisonger disables the white wire loop when they do their conversion also.

So I'm assuming there is nothing wrong with the tachometer. I need to look into other areas. The spark plug wires? The Lucas sports coil or pertronix?

 

[AUSMHLY]

Additionally, make sure you are using a long reach Suppressor type plug. If the radiation from the ignition wires affected the Pertronix you would get misfires. Yes I use the same set up and have for years no problem.
OH!!!!, and the radiation should also make a racket in your radio system.--Fwiw--Keoke-

Hi Keoke,
I don't have any running problems. No misfires. I also don't have a radio.
What long reach suppressor plug are you running?
You have a Lucas sports coil, pertronix and you're negative ground?
Roger

 

[tahoe healey]

Roger, can you go badk to points temporarily? If so, use an external tach and get a reading then set up the electronic again and see if you get the same readings. It may save you from changing out the wires.
TH

 

[Keoke]

What long reach suppressor plug are you running?

Bosch Platinum Spark Plugs,Type: WR7DP with Bosh suppessor caps screwed on to 7mm High performance stranded copper wire.

You have a Lucas sports coil, pertronix and you're negative ground. Y!!! Roger.

Would not go any other way,---Keoke--

P.S. I noticed you do not have a LUCAS distributor cap I made sure long time ago I had nothing else and it say "Made in England" Yes they are much better than any aftermarket cap I have seen.

 

[AUSMHLY]

OK guys. I'm going to try a set of 7mm Pertronix wires.
7MM “Stock-Look” Plug Wires

Now you can get a "stock-look" spark plug wire, that performs! We've designed these wires with the same core that we use in our 8mm wire. The only real difference is the 7mm flat black silicone jacket that hides its performance potential from the naked eye. Get the best of both worlds with "state-of-the-art performance and a stock look."

These wires will fit most original wire looms. Select a custom tailored set for a great out of the box fit or a universal kit to match your unique engine and wire loom configuration.

Features
Two current paths for reliability and redundancy.
Primary path: Spiral wound stainless steel alloy.
Secondary path: Carbon impregnated fiberglass center core.
7mm Silicone jacket to resist high temperatures, moisture, oil and chemicals.
EPDM (Ethylene Propylene Diene Methylene) rubber inner insulation for superior heat resistance and prevention of arcing and voltage leaks.
Fiberglass reinforcing braid for added strength and flexibility. Lifetime Warranty.
Flame-Thrower "Stock Look" 7mm Universal Wire Sets
Universal 7mm “Stock-Look” spark plug wire kits featuring 90° or straight spark plug boots. Each universal set includes terminals to fit both male and female terminal distributor caps.


Pertronix tells me not to use the side entry screw in pin style cap I currently have.

What's the best top entry cap for the stock Lucas distributor?
And a link to where to purchase please.

Cheers,
Roger

 

[GregW]

Hey Roger,
IIRC the cap you want is for a TR6 dizzy.

THIS might be what you're lookin for.

 

[Bob_Spidell]

... Pertronix tells me not to use the side entry screw in pin style cap I currently have.

I doubt they will fit/work with a stock coil, either.

 

[AUSMHLY]

... Pertronix tells me not to use the side entry screw in pin style cap I currently have.

I doubt they will fit/work with a stock coil, either.

Why do you say that?
I have a Lucas sports coil. I don't see any reason they will not fit it, being both the stock and Lucas coil accept a rubber boot style fitting.

 

[Keoke]

... Pertronix tells me not to use the side entry screw in pin style cap I currently have.

I doubt they will fit/work with a stock coil, either.

Well the " screw in pin style" works with that carbon string wire they should also work here.

Similarly ,if the wire fits a stock distributor cap entry it should also fit a stock coil.--Keoke

 

[Bob_Spidell]

... Pertronix tells me not to use the side entry screw in pin style cap I currently have.

I doubt they will fit/work with a stock coil, either.

Why do you say that?
I have a Lucas sports coil. I don't see any reason they will not fit it, being both the stock and Lucas coil accept a rubber boot style fitting.

M BJ8 has its original coil. It has a plastic, screw-in secondary lead connector that would not work well with spiral-wound suppression cable. With the stock Lucas coil--and stock stranded-wire cables--you run the wire strands through a small brass washer, then fold them back. The plastic screw-in 'collar' holds the washer, and the wires, against the inside of the coil secondary connector. The spiral-wound cables are relatively fragile and would not lend themselves very well to being stripped of their protective sheath and bent back. That's also why you shouldn't use a stock cap with these cables--the sharp pins in the cap damage the spiral-wound carbon conductor (I tried spiral-wound, 'modern' cables with the stock cap and coil and had mis-firing).

AFAIK, Lucas Sports Coils were never 'stock' on any Healeys. But, if the Sports Coils have the more contemporary, crimped-on style termination and a rubber boot it should be fine. Also, it appears--from pictures, I haven't seen a Sports Coil in the flesh--that the Sports Coil uses spade lug connectors, whereas the stock coils use round, screw-on type lugs on the primary connections. I've never seen a stock coil with plug-in, rubber booted primary connections, but of course that doesn't mean they were never used, or someone didn't add it after-the-fact (the screw-on connector had internal threads on the coil so a boot should fit over the outside of the terminal just fine). I do know there appeared to be some variation with some coils marked '+/-' and some 'CB/SW.'