Ignition Coil Advice Please

[Steve]

Afternoon all and just hoping I can pick all your brains a bit.

Had a small issue with the Polara this week and have narrowed the issue down to the coil.

Just a tiny bit of background before I get to my question. My car has GM style HEI ignition with an MSD Blaster 2 coil and the ballast resistor bypassed. A few weeks ago, I was fiddling around and left her running on the drive. After about 30 mins of distraction etc, she just cut out, dead. Wouldn't start at all and as the light was going, I left her and had a look the next day.

Following day, started fine, ran great andI just thought it was an freak instance of Moparness.

A couple of days ago I went out in her, did about 20 miles with no issues and stopped at some shops. About 20 mins later, got back in and she wouldnt start. Did the usual stuff (checked fuel to carb, swapped to spare HEI mounted next to main one, hotwire to coil etc) and worked out that although there was a spark from the coil, it was very weak and virtually non existant at the plugs. Swapped the coil for my spare in the boot and she fired up instantly and ran perfectly all the way home.

My thoughts are that as the coil is mounted in the factory position on the intake manifold, it has either just failed or it was getting too hot. Ive read up on it several times over the past few years and was under the impression that the MSD coils can be mounted horizontally or vertically. I then read somewhere that they must be mounted vertically.

Im planning to move the coil to the radiator support and mount it vertically. Hopefully it will stay much cooler.

My questions are .... is there a better location from experience than the radiator support to re locate it to and has anyone got any definative knowledge of the vertical/ horizontal argument please?

Many thanks, Steve

PS I still love her....she has only let me down once before in 15 years of ownership and that was on the morning of taking her to the NEC stand not long after I bought her. I had disconnected the auto choke as she kept flooding and I didnt know how to get her going properly without a choke in the cold. Thanks to Ivor and TerryR, I got there and realised she needs much more pedal pumping than I thought.....ie....more fuel....its a steep learning curve

[cadboy]

Hi Steve,

How old was your old coil?
they are know to fail.

and as on your car and many others the coil has been as factory fitted all its life, so I don't think how is mounted and where is mounted makes that much difference.

[rocket70]

I like Blues inside hinged tray that he has under his dash and mounts all his electrical items on there.

Keeps it all out the heat and tidies the engine bay up.

[Dave999]

HEI module uses a current limiting process, linked to reducing dwell just enough to avoid over heating at low rpm, it expects the coil to be the original
so idling away at 900 rpm should have seen your module go into a mode to avoid coil overheating but its not an original coil so goodness knows if that was good enough.
presume it boiled its oil

solution

Use one of these. open frame laminated frame coil plastic potted No oil.

buy from standard replacement range i dare say a coil for $7.99 will work but id rather pay $19 and get one with the mounting bolts as well

https://www.rockauto.com/en/catalog/che ... +coil,7060

the square ones proper little mig welder of a coil...

you need to work out which side of the connector is coil + and coil -
but other than swapping to spades and using a short standard ignition lead as your King lead to the coil Jobs a goodun

i just made a mount out of C section aluminium to mount it where the original went

open up plug gaps to 45 thou and make sure your leads are good

if you really want to go to town the original chevy truck and car coil bracket from 1975 76 six cylinder trucks is a good piece
space to mount coil heat sink and HEI module.

a wealth of info here

https://www.slantsix.org/forum/viewtopic.php?t=15779

if you want to implement a "module protecting" diode like jaguar used on their HEI equipped XJS let me know and i'll dig out the part number probably cost more than the coil


Dave

[Steve]

Hi Ali,

Thanks for the advice.....its about 5 years old and so done about 6000 miles or so. I definately think getting the heat from being sandwiched inbetween the intake manifold and the air cleaner isnt doing it any good though as you say, they do just give up at some point. I was under the impression the Blaster 2 coils could gbe fitted at any angle but the seed of doubt was put into my head when I read they have to be vertical.

Thanks Rocket...all of the work Blue does is on another 6 levels up from what I do. Always very impressive. As Im not too bothered about stuff being out of the way and super tidy in the engine bay, I will probably stick to relocating it to somewhere I can access easily if I need to. Thank you very much though for pointing out the option as per Blues car, appreciate it

[Steve]

Sorry Dave, just seen your reply, will read now

[Steve]

Thanks Dave, I will definately study all of that later when I get in. Thank you as always.

A new MSD coil has just arrived on my doorstep so think the option you are suggesting would be for consideration when this one has expired but I will be very interested to read that link you posted over a coffee later

[Steve]

Morning Dave,

Had a good read of the link you sent and that is definately the way Im going to go as a future project. The diagram in the threre is fantastic, as is the content of the whole thread. A great read!!

I think my pal from Canada is coming over in May so will ask him to get the parts for me on one of his regular Rockauto orders and spend some time getting the stuff together to do it all.

Interesting bit on the fact that distributor caps arent what they used to be.

If its no bother, that part number for the diode would be great please, thanks.

Thanks again Dave, appreciate all of your knowledge and help,

Cheers Steve

[Steve]

Thats the coil moved and, due to an oversight on my part, new coil HT lead arrived today. All seems fine on a run out. I ran out of heatshrink so will get some for the terminals on the leads. Will also tweek the routing of the HT lead, photo shows a quick fit to test the car on the road. Sorry, not sure why its sideways

Used a company called Powerspark Ignition Ltd.

https://simonbbc.com/

Cant fault them. Phoned Monday morning, discussed my needs, they made a couple of leads up and posted, arrived today!!!!

Thank to everyone for their help

[Dave999]

diode

VS-40HFR40 Diode Stud mount

https://www.ebay.co.uk/itm/204060233388

these are massively over specified you will only ever be buying one


notice the way the little diode logo is on it and compare with circuit below...stud goes to earth an arrow bit points at solder contact

why?

because it was part of the original specification given to Jaguar by motorola, when they came up with the CEI AB1 module for the XJS 6 and 12
an expensive aluminium box filled with magic fairy dust and an HEI module

the original transistor set in the GM hei module could not stand more than 350V back emf, i.e the recoil action from triggering a spark,
so they used a zener diode to sink/clamp/divert the proportion of that recoil voltage above 350V to earth protecting the module

modern HEI modules can cope with 450V, and in a standard application the diode is no longer used, We are not the standard application and there is nothing to stop a coil firing wide gap plugs into a high compression cylinder from kicking back 500-600 volts, and when it does that it damages the module and can throw your tacho into a wobble.

can't get a 350 reverse polarity zener diode anymore so a 400V is the best bet.

just bolt it into your bracket and run a wire from the contact to the coil negative

can apply this to a mopar set up as well.....

doesn't impact coil "filling" think of it as garbage collection after spark has fired the cylinder.....

with no AM radio and No CB you don't need the capacitor shown anymore

drop me an IM with an email address, and i'll send you some nice PDFs explaining why, HEI has some limitations but provides spark energy similar to an MSD 6AL. can't post useful docs on here....blocked


dave

[Steve]

Cheers Dave, PM sent

[Dave999]

Hi Steve

The writings of a Dr Hugo Holden are on their way to you


sorry for delay in replying...i had not spotted your february update

Dave

[Steve]

Thank you very much Dave, will have a good read over the weekend. Cheers