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Bowers spark plug cross referencing.

viv w

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Hi All,

 I have 18 new Bowers C78C spark plugs that I bought, hoping to use them in my Model A Ford or 26 Chrysler. Does anyone have a cross reference chart to tell me what these plugs fit, or what these plugs are equivalent to in Champion, NGK or other makes.



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The correct plugs are easily available for your cars and that's what I'd personally recommend. 


For the Model A, If you don't want to spend the bucks for the authentic looking 3X you can buy Champion W-18.  You can also find some original early Champion C-4s on ebay reasonably too.  They should work ok in the Model A, although they weren't really introduced until 1932 (for the new V-8).  If you want to go cheap, Champion W18s would work and I see Rock Auto has them available for just a hit over $6 each.  Most Model A Parts Catalogs also list a Motorcraft plug as low as $5 each.


The modern recommended plug for your Chrysler is a Champion W16Y.  The C4 should also run in the Chrysler and is listed in a reference sheet I've got from Champion that was published in 1972.


I don't have a conversion for the Bowers but if you measure thread and reach, you can always give them a try.  Personally, I'd stick with the Champions.


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Thanks Terry,

I have been having problems with my model A, it gets very hot, very quickly, causing the condenser to breakdown and misbehave. I have tried another carb and distributor off a friends car and it did not cure the problem, I have changed coils and condensor and flushed the motor to ensure the block is free of sediment. My radiator has a new core and I have swapped radiators with a car that runs much cooler than mine. The waterpump is new and I have checked for bubbling in the radiator and manifold leaks. It had me stumped.

 I parked the damned car and have been rebuilding another Ford A for a friend, which is now finished, runs very sweetly and does not overheat, not even when pushed hard.

 I decided I will not be beaten on my own car, so rechecked everything, comparing what I had done with the other car. It then dawned on me that my A ran W20 plugs and the other has C4 plugs. I remember a friend many years ago changed plugs on his Austin 10 and it instantly ran hot, as the plugs were the wrong heat range. 

I think the W20 is too hot a plug for the model A motor. I have swapped them out for some NGK A30's that I had lying around, these are a much colder plug, the motor seems happier and tomorrow I will take it for a test drive and see if the car runs cooler. The NGK A30 may now be too cold a plug, but if it cures my overheating problem, then I know I'm headed the right way and will import some more X3 or A4 plugs.

 The 2 Chrysler's that I own , both should have C5 plugs, which I believe is superceded by the W16Y. Both these cars require major restoration, so I don't need to worry about plugs for them right now.

 The Bowers plugs I bought cheap in South Africa, not thinking about heat range for them, they are 18mm plugs, but I would still like to find out what they equate to in the heat range.

Thanks for your input, it is appreciated.




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I think you've got it figured out - those W20s are not right.   If your Bowers plugs are 18mm they won't work in either car.  Your A and the Chrysler both use 7/8" thread plugs.

Make sure your timing is right and fuel mixture is set right too. 


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