Ford V8 spark plugs

[Richard Farrant]

As far as I am aware, all Ford V8 engines in WW2 era vehicles, had 18mm spark plugs,. These plugs are now expensive and limited choice of grades. I would like to take advantage of a wider range of plugs at half the price by using a 18 mm to 14 mm adaptor in the plug holes.

My question is, what 14mm plug, using Champion, Bosch, NGK, etc. numbers as a guide, would be equivalent to the original 18mm ones ?

This is for a British built V8, but I suspect they were all the same (?)

[Rhett Fisher]

Hello Richard,
I use 18mm plugs in my vintage motorcycles and I get them quite easily from any NGK stockist at a price similar to common 14mm types i.e. about £3.00 each. I wouldn't have thought the conversion costs were worth it as the money would buy enough plugs to keep your V8(s) running sweetly for a year or twenty!
NGK standard 18mm plugs are A7, which should be more than adequate for most V8s, or the slightly harder (colder) A8 if you have a motor with cylinder heads that glow in the dark!
Another NGK option is the AB7, which is a standard 18mm plug but with 14mm (21mm AF) hexagon. I use these in my pre-war Douglas bikes because space is tight between the pushrods.
A possible problem with inserts is poor heat transfer, so harder plugs may be required. Also, the 14mm plugs in CMP (Mercury) engines are 7/16th inch reach (trust Henry to be awkward!), which are catered for by the Champion H types. I assume the thickness of the heads has something to do with this odd dimension.
If you have any trouble obtaining suitable plugs, let me know and I'll do my best to help.
Regards,
Rhett.

[Neil Ashley]

Richard

Unless my memory is giving out, Canadian V8 engines take 14mm plugs.

[Richard Farrant]

Thanks Rhett, and Neil,

I had seen these 18mm plugs at much higher price, but £3 is more realistic ! The Green Spark Plug Co. website was off when I looked, they are back online now

[Lynn Eades]

To my knowledge (which is regularly adjusted) pretty much all Canadian and American Ford v8's were 14mm. Only the Brits stuck with the(archaic) 18mm.

[Richard Farrant]

Originally Posted by Lynn Eades

To my knowledge (which is regularly adjusted) pretty much all Canadian and American Ford v8's were 14mm. Only the Brits stuck with the(archaic) 18mm.

Actually Lynn, most of the British engines at that time (WW2) were 14mm plugs. It was only old Henry Ford who was still using 18mm, also in his tractors at that time. Talk about a "stick in the mud", Fords continued until the late '50's with 3 speed, side-valve cars..............oh thats another subject

NGK A6.

A =18mm 6 = middle heat range.

Maccess had plenty, mainly because Rory kept buying boxes for the Morris-Commercials and the computer kept re-ordering. . . . . . . . . They've sussed it now unfortunately.

I had the pleasure of meeting the NGK rep in there one day and asked why so many old plugs were now replaced with a single type.

Better materials - generally if you mix air and petrol at 14:1 it goes bang with the same properties and heat no matter if its in your lawn mower or Ferrari. All the complex numbers just define the particular mechanics of suppression, thread reach, seating and hex etc; as a glance at the nomenclature chart shows.
http://www.spark-plugs.co.uk/pages/t...ymbol_code.htm

A6's (7's would do) have done thousands of miles in the M-C's and a few hours in my pre-war Allen Scythe too, Daves F15 has had BM6ES from the word go; no B6ES on the shelf so used lawn mower plugs. . . . .M = compact insulator.

R.

[Richard Farrant]

Originally Posted by Richard Notton

NGK A6.

A =18mm 6 = middle heat range.


I had the pleasure of meeting the NGK rep in there one day and asked why so many old plugs were now replaced with a single type.

Better materials - generally if you mix air and petrol at 14:1 it goes bang with the same properties and heat no matter if its in your lawn mower or Ferrari.

Thanks.

Yes, the beauty of these modern plugs with copper core, NGK being one of the first, I recollect, they have a wider heat range so no need for such a wide range of plug grades as in the old days.

[Lynn Eades]

Richard I was ONLY referring to Fords,and yes, I remember the "100E Defect" that my mother owned.(3 lousy ratios, and gutless)
Back to the 18mm plugs, Ford persisted with them into the 80's with the D series petrol trucks. (I think that 300 cu in. petrol motor started life as the Mustang motor of the fuel crisis.