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MG TD TF 1500 - Plug and Distributor lead resistance Pertronix

I think I have read most of the former posts on this topic but to check ...

My TF1500 has a correct original (rebuilt) distributor and Lucas pertronix (-ve Earth) 'Ignitor' system. It also has the recommended Pertronix high output coil and (to my question) magnecore High Performance Ignition cables (metallic/inductive/suppressant) that came with the coil. The resistance readings on these on the bench are:

#1 800 Ohms
#2 700 Ohms
#3 630 Ohms
#4 560 Ohms

I believe that these are all in spec.

However I note that the main (centre) lead from the Coil to the Distributor shows 1200Ohms. Does that seem high?

Many thanks Merv
M Hyde

Merv, which model of Pertronix Igniter have you installed? Bud
Bud Krueger

One of these thanks Bud. 12V and -ve Earth.

LU-146P12 Ignitor Lucas.
M Hyde

2.2K ohms / foot
If your coil lead is about 6-7 inches long then it is good
It's good anyway, 1.2K is a good lead, nice low resistance
Question--Is the magnet ring a nice firm/secure fit over the distributor cam.
On another point , which I thought that was what this was going to be about---what spark plugs are you using.
William Revit

Merv, this version of Pertronix Igniter, with the magnet sleeve, doesn't need resistance wire ignition cables. The only resistance value of concern is that the coil primary wiring has a resistance of about 3.0 ohms. The OEM ignition wires are fine.

The S versions of the Igniter, without the magnet sleeve, need to be wired in with resistive , high voltage, lead wires. This is to minimize the RF noise effect upon the Igniter module. This version of the Igniter is like a relay being tripped by the magnets. The S versions have complex circuitry that sense the differential effect of portion of the cam lobe that is passing the sensor at the peak instant. Any RFI noise can affect the timing. Resistive wiring (or plugs) reduces that noise while limiting the current through the spark plug. 'Modern' ignition systems are susceptible to RFI noise and need suppression. That's what 'R' spark plugs are for.
The NGK BPR6HIX (4085) plug seems to be a good one for use with Pertronix systems.

Bud
Bud Krueger

Thanks Bud and Willi. That is interesting Bud about the leads with this trigger with the magnet sleeve. It was fitted by the PO some years ago who was insistent that it needed the high output coil and the set of Magnecore wires. RFI noise would not seem to be a problems I don't use a radio with the car. Is that their prime purpose? Will using the current wiring (primary and plug wires) with their above listed resistance values, affect the operation of the Pertronix? If so I have the original wires.

Willi I am using NGK BP5EY at the moment. I have considered BP6EY and even have a set. Would they be better? Yes the magnet ring is a nice firm/secure fit over the distributor cam.

Bud I can see the iridium ones (NGK BPR6HIX (4085)) for sale here at a reasonable price but is there added value in their use?

Very best Merv

M Hyde

Hi Merv, IMHO that wiring should have negligible affect on the Igniter. Virtually akin to an 'R' spark plug.
See http://www.ttalk.info/Failure.htm for that which set me onto the 'S' series, i.e., no magnet ring.

It would be interesting to see what affect would show up on an ignition analyzer with the OEM wiring vs. the Magnecore wires. I just reread your initial text and I see that the Magnecore wiring is from Pertronix. It's optimized for the Type 'S' Igniters. Buying that would have saved ne a lot of hassle in making my ignition wires.

My LU-146LS shows RFI problems above 3500 rpm if I run with OEM wiring. The resistance in the 4085 plugs has a little help at about 4000 rpm. I haven't considered adding a resistance into the coil to distributor line.
My Igniter is about 12 years old now and works fine.

Cheers, Bud

Bud Krueger

Thanks again Bud and Willi. That is a very interesting TTTalk link. My collar is narrower I believe and with the existing rotor fits nicely under the sprung carbon electrode/pole under the centre terminal of the distributor cap.

I will leave the wires/leads as they are but remain interested in the most suitable spark plugs for this 1500/XPEG motor. I have some BP6ES ones also.





M Hyde

Merv, you have me befuddled by that last Image. My eyes want to tell me that it says 'Igniter LS' on that label. Could you please get a straight on shot of that label?
I see the stamping of 'LU-146P12' on the fixing plate.
Could it be that you have a hermaphrodite of some sort?

Please show me what's there.

Bud
Bud Krueger

Just run what you have there, it's a good coil, the leads are nice low resistance, if the outside insulation on the leads are good I'd be sticking to them---The sleeve on your distributor looks to be the correct one, -why I asked about that was ,I've seen a few with a loose fitting sleeve and too thick at the top preventing correct fitting of the rotor-yours looks good.
Sparkplugs-
I'm a NGK fan --been using them for years

WARNING -There are some copies about that are rubbish
They're in NGK lookalike boxes and look for all the world like NGK plugs--but they're not and they breakdown easily under load
The only way to pick them is the machining of the bottom section where the earth tang attaches to the plug itself---With a genuine NGK ,after the thread finishes there is a small straight section that the earth tang is on--with a genuine plug this section is straight sided and finishes off with a sharpish right angle flat end----With the dud plugs this end section isn't straight at all, it looks more of a moulded/rounded over piece and has a rougher sandblasted look to the finish instead of the genuine plug's nice straight machined look------be carefull when you're buying them

As far as BP5ES/BP6ES goes
NGK plugs are very forgiving with heat rages, you can be a bit out without any disasterous effects
6 is cooler than 5
5 would suit more shorter running, it'll probably run maybe a little better during the warmup cycle
6 would still be fine, it's the normal plug for MGB's
just depends really how you drive
If it's just puttering around town with the occasional squirt out the road, 5 will be fine/best but if you tend to stoke it into it a bit or have some hilly countryside then 6 might be more suitable, but as mentioned NGK's are forgiving and their plug ratings are a lot closer to each other than most makers so not as big a jump-

With what you have there you don't want or need resistor plugs and iridium plugs are a complete waste of cash--they were designed for very long service intervals for modern cars and rarely make the required distance anyway---An occasional new set of std. plugs like you have is the go, keeps it all fresh and the wallet happy

IF you were to run resistor type plugs with the setup you have there the result is lower spark voltage and the risk of firing down the outside of the insulator
I've seen them actually burn the resistor out of inside the plug on a set of fairly new plugs-not on an MG but,--you don't need/want them on your car, just something else to go wrong

willy
William Revit

Good advice Willi. I have some unused Champion NY5 plugs still in their boxes. They will stay that way. Interesting about the fake NGK plugs! I need to do a long highway run to check plug colours very soon. Idling is not a good guide.

Hope the summer in the "other" Island down there is a good one. We have had almost a metre of monsoonal rain up here. Send us a photo of the Aurora Australis at some stage.

Cheers Merv
M Hyde

Summer's been good so far--uv reading is sky high though, but we're used to that---Tourists get caught out big time though
Wednesday was a weird day 40mm of rain, wind ,thunder/lightening and cool temps--Thursday was a bit of a recovery catch up day then today (Friday)it's summer again, - yay- apart from the uv
I hear you're in for another rough time up there-

The aurora's have been magic but just about all over now-'till next time---really weird though they're a bit hard to see by eye but if you're lucky and take a pic with the camera(or phone)they light up like anything

Stay safe
willy

https://www.buzzfeed.com/annamendoza/lady-aurora
William Revit

Okay, Merv, you got me. I can't imagine why someone would put the LU-146P magnet ring over the distributor shaft being sensed by an LU-146S. But, apparently it works. It'll require some sort of RFI/EMI dampening.
Maybe I'll try slipping my old magnet ring over the shaft to see what happens. I'd just hate to damage the electronics module in the 146S.
BTW, I've been using BP6ES plugs for 10+ years.

Bud
Bud Krueger

Bud it may be a mix and match but it works fine. I guess a magnetic trigger collar can work the same with various sensors? I had it tested by the folk who did the distributor rebuild for me last year. The PO installed this years ago. I have attached a couple of images of the sensor. I have a spare Ignitor (unopened) and the sensor is just labelled "Pertronix", with a baseplate with LU-146P12 also. The collar with it looks thicker however.







M Hyde

Thanks Willi. Those lovely images of the Aurora Australis are great to show folk in the Northern Hemisphere. Hot as hades here everyday with humidity in the high 80's. MG drives are confined to early mornings! We have had over 500mm (20+ inches) of rain this week and a second cyclone coming!
M Hyde

I think they just market them strangely Bud
I looked up the 'info' of one sold as 'lobe sensing' and in the info it said-
"Rotating cobalt magnets trigger a Hall Effect integrated circuit"

sounds a bit weird, you'd think if it was magnets it'd be inductive pickup, but then it's in writing and they work---weird

https://pertronixbrands.com/products/pertronix-1181ls-ignitor-delco-lobe-sensor-8-cyl

willy
William Revit

Bud - correction- I can see your point on the LS on my sensor (different model) - which is on a LU-146P12 plate. The earlier (unused spare) model Pertronix sensor that I have has the same numbered plate and has a LU142 collar. See image Maybe I should switch them over (after checking collar thickness) and see how it goes?


M Hyde

Bud, I checked the fitment of the (spare) collar (LU142) with the other Ignitor set that I have and it is (1) too thick and would interfere with the carbon electrode on the distributor cap and (2) does not fit the lobe dimensions of my distributor shaft (D2A 4 etc ). I guess the existing collar is one that fitted well. That does not really answer your question about the LS model sensor and the use of a magnetic collar!
M Hyde

Merv, could you tell me what distributor you have there? Thanks, Bud
Bud Krueger

As above Bud, a rebuilt original D2A 40367.
M Hyde

I’m awfully glad the issue of plugs has been brought up. I’ve been using the same plugs for years. I have boxes of new N5 and N5C sitting on my shelf, but so far, there seems to be no need to change .. But hey, I’m naïve! Car seems to be performing OK.

What about these new technology plugs in iridium, platinum, or good ‘ole copper?

Some plugs come factory-gapped at .050 or more. By comparison, some of these gaps seem ridiculous.

I have an early Pertronix that has performed without flaw since 2006, I have a Pertronix ‘Flame Thrower’ coil (40,000 volts) but haven’t installed it yet.

I need some advice. What plugs and what gap? And should I install my new coil?

Gord Clark
Rockburn, Qué.
Gord Clark

Gord, the concensus seems to be NKG BP5 or BP6 these days. They are pretty good. With the Pertronix most use a wider gap because of greater spark intensity available and set them between 30 and 35 thou.

Bud did you find any info on units for that distributor? PowerSpark systems make one for that model in the TF. See: https://classiccarpartsaustralia.com.au/powerspark-electronic-ignition-kit-for-4-cylinder-lucas-d2a-distributor-k32-powerspark
M Hyde

PowerSpark UK


M Hyde

We are not the only people with electronic ignitions and plug wire problems. On a recent Roadkill episode, they went through several faiiled MSD boxes and distributors and finally figured out the solid core wires used were the problem. I have the slip on magnet collar Pertronix installed when they first came out. Still works perfectly! George
George Butz III

I'm running a (D2A) 40368A distributor in my late TD engine (28839). I've been using the LU-146LS with NGK BP6ES plugs for over 12 years now. I made up a set of 'modern' ignition wires to avoid the RFI and EMI issues with the Lobe Sensor Igniter.

To the best of my knowledge there is no standard Pertronix configuration that uses a magnet ring with a lobe sensor Igniter. The 146LS module provides an electro-magnetic field whose variation (by the cam lobe) is sensed by the Hall effect circuits. Merv's configuration is quite unique.

George, see this one:http://www.ttalk.info/Failure.htm

Bud
Bud Krueger

Bud I guess I could just remove the collar and see if the LS sensor picks up the lobes? Would be interesting. Also the PowerSpark UK version seems very similar to mine?
M Hyde

"'m running a (D2A) 40368A distributor in my late TD engine (28839). I've been using the LU-146LS with NGK BP6ES plugs for over 12 years now. I made up a set of 'modern' ignition wires to avoid the RFI and EMI issues with the Lobe Sensor Igniter.

To the best of my knowledge there is no standard Pertronix configuration that uses a magnet ring with a lobe sensor Igniter. The 146LS module provides an electro-magnetic field whose variation (by the cam lobe) is sensed by the Hall effect circuits. Merv's configuration is quite unique. "

Bud, removing the collar on the lobes did not work as the LS sensor did not detect the field variation from the lobes alone. I am working with Pertronix in Australia as they feel that the Ignitor 2 would do the job and it has two advantages: (1) polarity protection and (2) 'key left on' scenario protection.

M Hyde

Something isn't right there. I have been using a stock LU-146LS Igniter for over 12 years now. It does NOT have a magnet collar. It strictly senses the dynamic shape of the lobes. I went to the lobe sensor after my disastrous failure with the LU-142 magnet collar on my original LU-146 Igniter, see http://www.ttalk.info/Failure.htm. The LU-146P uses a magnet collar.

I wonder if your LU-146P12 on a 40367 is the right configuration for an LU-146LS. The specs for use of a 40367 differ from those of a 40368. The LU-146P didn't exist when the LU-146LS was available. I think that's from the 2012 Catalog, page 14.

Strange things. Bud
Bud Krueger

The way i see it, it has to be a LU149P12-it works as that and that's what's stamped into the plate-
I'm wondering if it was bought new just as the LS units were starting to be produced and got the wrong sticker stuck on it---easy fix--it works ,take the sticker off and forget about it.--interesting though

willy
William Revit

It is odd Bud. The lobe dimensions of the 40367 (flat-to-flat is 16.4mm and lobe-to-lobe is 19mm) may differ from the 40368 perhaps hence the need for the collar to get closer to the sensor?

I have Pertronix on the case here and interested to hear what they say. In reality I am only concerned if I am losing some integrity of the effectiveness of the current unit.
M Hyde

I think Willi has it right. He said:

"The way i see it, it has to be a LU149P12-it works as that and that's what's stamped into the plate-
I'm wondering if it was bought new just as the LS units were starting to be produced and got the wrong sticker stuck on it---easy fix--it works ,take the sticker off and forget about it.--interesting though"

I just heard back from Pertronix Australia and their response is that

"The LS modules definitely only work with lobes so I have to assume, considering that one has been running, that it has an incorrect sticker on the module"

Now I can either keep the working existing system or invest ($$) in an Ignitor 2 system!
M Hyde

Well, Merv, it sounds like you have a system that works with the magnet collar. You should be able to get away with OEM wiring. That should provide you with strong sparks in the plugs since you can minimize the use of resistored plug wires. You'll just want to watch for 'noise' in the advanced spark patterns at high engine speeds, i.e., >4000 rpm.

It would be interesting to see what the spark pattern is like when viewed on an ignition analyzer. Should be a fine system.

Bud
Bud Krueger

Thank you and Willi for your help Bud. My system is functional and there is no sign of spark breaking down. I rarely exceed 4,000 rpm with the 5 speed gearbox. The mystery of the LS sensor, with a collars, is I believe, explained. I have in my toolbox a new unused Ignitor 1 with a collar and a re-built points plate so any 'on the road' failures should be covered. My peripherals (coil and leads) all seem on spec as well.
M Hyde

Merv, funny you should say that (your last sentence) - I'm in the process of trying an Accuspark setup following the sudden demise of an old Lumenition kit in the B. I plan to put a spare baseplate and points/condensor set in the glovebox. You never never know! John o' the north.
J P Hall

Always good to have a back up John. Hope you are OK up there?
M Hyde

Your penultimate sentence, of course but you picked it. Cyclone? - nah, just a puff of wind, and a few hours down the road from us this time. Townsville can have it!
J P Hall

Since day-1 I've stored my original OEM baseplate in my toolbox. Standard routine at Car Club programs was to show how easy it was to install a Pertronix system and then show how easy it was to re-install the OEM points system and fire up the car. Once it failed. I forgot to install the rotor. Bud
Bud Krueger

This thread was discussed between 17/01/2024 and 24/01/2024

MG TD TF 1500 index

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