The Stovebolt Site Forums The Shop Area The Electrical Bay Is there a reason for the coil to be installed upside down?

I noticed in the truck shop manual and assembly manual for the 1947-1954 Chevrolet truck that the coil is installed upside down. the PO of my truck installed it with the wire terminals facing up. I have converted to a 12 volt system with the Pertronix electronic ignition unit and a Flame Thrower coil. Will it make a difference if the coil is upside down or right side up?

I've noticed that too & have wanted to ask the same question. I came to believe that it might be upside down so as to make more room below. The dizzy is right there & also the plugs, so mounting the coil pointing down & pushing it upwards makes more clearance.

makes no difference, that's just the way the factory did it those years, possibly to allow the oil that can bubble out of an overheated coil to drip on the ground instead of getting all over the coil mounting hardware

Bill

And I always thought it was that way so it was out of the way when adjusting the valves...leaky coil? That has got to go.

Given the minimal amount of splash shielding in a stovebolt engine compartment, there was less of a chance of an ignition system drowning out when splashing through a puddle or fording a creek to get to the next pasture if the coil wire was pointing down. Some of the Brit sports cars mounted their coils the same way for the same reason. Spit on the sidewalk 3 blocks away, and a Jag XKE would drown out! Of course, the Brits drink warm beer because they've got Lucas refrigerators!
Jerry

Oh yeah: Lucas the inventor of Dark. Found among other marques including but not limited to: Triumph, BSA, MG, Aerial, JAP, the above mentioned Jag, and Range Rover in its many variations. Gotta love Brit electrics.

I want the open wires to be as high as possible away from splashing. I want the rubber cup not to act as a water catchment when down. I want easy access to the wires. My opinion is they were trying to get it into the air flow.(fan and forward motion)and back then before they new how to completely fill, it made the oil stay near where they wanted it to stay.

I always enjoy know-it-alls at car shows lecturing me about how my coil is 'upside down'. But then, I am the jackhole at car shows who points out to owners of ADs who have their coil installed incorrectly.
Carl

It is, in fact, vintage correct to be upside down. You are correct jackhole. We totally bitchiner TF guys run ours straight up. It's also definitely a V8 thing.

On earlier versions, '47 and earlier I think, the coils had the primary terminals on one end and the high voltage terminal on the other. Mounted primary up.
Have one on the '48 2 ton because it came with it ind it still works (besides the big white porcelain insulator looks cool).

Well here is another question....My coil bracket which I was told by the PO is original does not look like the one in the assembly manual. My coil bracket has one mounting ear over the other and mounts on one bolt near the push rod cover and valve cover. It does not have a tang to mount a radio noise suppressor, but the coil screw and nut are in the same place. I was told by a real 'ol timer who worked for GM/Chevrolet Division in Duluth, Georgia that what ever they were supplied with on the day of assembly is what the installer put on the vehicle that day....or week. So is it possible that the assembly manual only gave them direction, but not specific parts designations for assembly?

yes, probable, although the part numbers indicated in the manual were what was used around/after the date of the specific page - the AD assembly manual is primarily 1954/55 I believe so can't indicate much about previous years [the TF 55-59 manual is actually from 55, so no 58/9 data included] .... the assembly manuals were originally loose leaf guides for line supervisors, pages replaced as changes made by the engineering dept, not what we have now as reproductions

Bill

The only thing worse than a jackhole? One that is correct.

I have always considered my Advance-Design coils to be right-side down and the flat-side on top.

Just a matter of generational perspective?

The Germans liked the coils facing down too. On ACVW engines the coils were mounted terminals down and as close to the dist as possible all through their production from the 40's well into the 80's.
Their engine compartments were sealed to keep the hot air down and out and let the cool air in from the top which also worked well to keep water and other debris from splashing into the compartment. You just needed to keep those fuel lines properly servicesd but thats another topic

I figure the reasoning for terminal down coil mounting was to get the coil as close as possible to the Dist inorder to achieve the shortest high voltage coil lead.
I'll swag their thinking was that a short high voltage lead reduces voltage loss & RFI (on later radio equipped vehicles).
Other factors already mentioned probably worked into the equation too.

Had a fellow tell me the other day that my coil was upside down in my 49 3100 and that it was going to leak out the high voltage socket.
He doubted me when I said that was how it came from the factory

Can't wait for him to see my new high performance orange oil bath AC
Dave

Correct! The primary (high voltage) to the dist. was on the 'bottom' and the secondary from the points was at the the top for a long time. GMC did theirs the same way on the 270.

Something must have changed in coil manufacturing to allow all three connectors to move to the 'top'.

So upside down is the way it came from the factory? Really? Everytime I see one upside down, I FIX it. Seems kinda silly when it comes to connecting tachs, dwell meters, etc to have to figure out which wire is which upside down. I have enough trouble deciding where to put things when its rightside up! In this case, rightside up is upside down?

At what time in the past 100 years did the high voltage become "primary"?
Jerry

The only reason to have it upside down, which is really right side down, is to be "original". We don't mess with the coil very often. So those who want to look correct are correct. Those who want to have better access, etc., are happy and incorrect. Coils are shown, in Chevy Truck manuals, with secondary tower downward, up to at least 1959 on 6 Cyl. The functionality of either way is subjective. (I like up)
Correct= like factory installed and shown in various old literature for the year of the motor engine.

From the 48-51 On-line truck shop manual
Notice the coil's orientation in the cross section sketch.

You know,in looking at that schematic, the Engr's must have thought those electrons going downhill would flow faster

1938
https://www.flickr.com/photos/advance-design_parts_co/8437430111/in/set-72157632668391879
1941
https://www.flickr.com/photos/advance-design_parts_co/8583881002/in/set-72157633068187319
1951
https://www.flickr.com/photos/advance-design_parts_co/8603094476/in/set-72157633120087261
1954
https://www.flickr.com/photos/advance-design_parts_co/8256656804/in/set-72157632199330381
1956
https://www.flickr.com/photos/advance-design_parts_co/8525528671/in/set-72157632910502326
1959
https://www.flickr.com/photos/advance-design_parts_co/8323011271/in/set-72157632379796560

Hey Deve, take a breath man, you're going to turn yourself inside out (or outside in on 6V positive ground applications).

WOW....and I thought I was asking a simple question. I did realize this would create so much discussion. I guess a lot of you guys had he same question. I have come to the conclusion from these discussions, that the coil was originally mounted as I termed as upside down was due to the primary terminal on the late 30's to early 40's was on the bottom of the coil. The other reason this was carried on was for clearance.

If you do your own work on your stovebolt engines, it is easy to know which wire goes on which post, when the connection side is orientated downward (as GM sent them out of the assembly plant): install the coil with the ignition-lead connection-post towards the firewall, and with the distributor-lead connection-post towards the front of the engine? follow that logical habit and correct-side down is relatively easy to deal with.

Trivia question: on which GM straight six trucks (let's say 47-55) was the coil mounted with neither side up nor down?

Cabover models?? John

Yes, at least on my 54/55 GMC 350 2-ton.

Fixit: Actually I did not have that question ever in my mind. I have always mounted them with tower up and probably always will. Was just an interesting automotive history subject and a generational perspective study.

Whats nice about this discussion is, its all preference and nothing really changes. If your friend who is offended by your coil being top up comes over, you can loosen the screw, pop it out and put it in top down.

What?

And I thought we were friends?!
Carl

We are, you are editing me. the message was to Fixit58's comment. I am being set up. It's unfair.

I never was very good at rule following.

The coils were oil filled and inverting them kept the "business end" cooler.

Greg,

Is the business end the right end or the wrong end?

Or, is it the up-side down end or the down-side up end?

I hope you had a nice Easter.

Gravity helps the high voltage spark flow out the coil! Just kidding. On my 46 the security cable attaches to the top so it makes the ceramic insulator face down. They probably did that back then to reduce dirt and moisture from causing arcing to ground.

Thanks guys and happy Easter.

Tim, the business end would be the end that made you sorry you touched it with a running engine!

I did that only once, Greg - what a jolt.

I'm betting some doobie smoker put it in wrong, and the engineer said.. why not.. and there ya go! Once its in the pictures, its a done deal. LOL! Im sorry, but there is no intelligent reason to put it upside down.

A daughter learned when cooking a ham, to cut it in half. The daughter finally asked her mom. Why am I cutting the ham in half before cooking? Mom said because its how we have always done it. In asking Grandma, why do we cut the ham in half before cooking, she replied.. because that's the only way to get it to fit into my pan! If you don't get it, please just let it go! LOL!

Thanks Deve, I needed the chuckle.