I have a head with holes for the spark plugs have threads millimeter.
I would redo the biggest threads to mount the standard spark plugs .
What is the size of standard threads?
Where I can find a tool to make another thread?
Olivier ;It is 1/2 inch pipe thread you can buy it at a lokal hard ware store .But I think that your milimeter thread is standard for your car .I read somewhere that Model t's for export to Europa had Sparkplugs with milimeter thread .
See you and the car in France next year!!!
Original T heads labelled 'Metric' really weren't, they just had 14mm spark plug holes-std.
If your holes are damaged and you think changing back to USA specification is a cure...
The drill 17,4mm is recommended when a USA tap drill size is not available...and when you find a tap DO make sure it is 1/2" NPT labelled as that is the USA specification. The old British specification called 1/2" pipe is NOT the same thing- The American system uses a taper wedge of the threads...the old British system is a parallel thread which will not match American A25 or X spark plugs.
I would imagine a good local supply house would be able to get a 1/2 NPT tap...if not find a local factory friend where his factory uses American supplied equipment Americans were/are so slow in even thinking change, most American heavy machines STILL ship with tap drill/tap/die sets for maintenance when shipping something to the continent!
The Sparkplugs with milimeter thread standard is France, but the sparkplugs in mm are difficult to find and often of poor quality, for the models T.
The 1912 Ford is not completed for Vichy, therefore I will be with the 1924.
Thank you George, I will follow your you counsel
Where would you get NPT sparkplugs? Why not order mm sparkplugs from the US? They're popular in Z cylinder heads here.
There is a trick to the USA pipe thread cutting. So if you do decide to convert your head the trick is to wrap the tap with tape so that exactly 10 threads are exposed and ONLY tap that deep and never deeper. Otherwise the taper just gets too wide and everything sits 'deeper' than intended.
Why is it so difficult to get metric spark plugs??
Manuel in Oz
All modern spark plugs are metric.
Tapping a NPT pipe thread properly also requires the use of a tapered pipe thread reamer. Otherwise the efforts to tap the straight drilled hole will be very high.
Before you modify that original head with mm plug holes, why not find old original plugs in working order that fit metric.
Once you drill ream and tap with US pipe thread you can't go back to original.
You could contact the American Spark Plug Collectors, and see if any members can provide you with 4 metric plugs for the Ford. These were common in the day.
website of Spark Plug Collectors.
Here are some adv of Champion X plugs, 1913 and 1923 catalogs, showing metric size was provided.
Wouldn't be easier to install a head with standard threads? Shouldn't be too hard to obtain.
I think I'm right in saying the metric heads used 18mm plugs, which are not so easy to find now. Having said that, I find Tim Green lists 290 variants! Try http://www.gsparkplug.com/shop/spark-plugs/spark-plugs.html?diameter=31
And he will probably know which fits the Model T. Cheaper and easier than re-cutting the threads or buying a good low head.
I would think swapping heads would be the easiest.
Don't forget, this gent is not in the US, T parts are a lot scarcer in Europe - I think easy route is to buy the right plugs, they're only going to be less than $50 the set. And the car stays authentic.
How common are metric heads in Europe? How hard would it be to obtain one? Are they available in both high and low styles?
I've never seen metric spark plug threads in T heads in Sweden, guess it's a continental phenomena? How bout Denmark, Michael?
Assuming its an 18 mm plug, the Champion D-21 is the hottest one I know, its Bosch equivalent is a M10ACO. Champion D18Y, Bosch M8ACO is the next lower heat range. You might try a tractor dealer, such as John Deere and see what they have to offer. Some lawnmowers use these plugs also.
They are readily available on the Internet in the US. Have you tried the Internet in France?
Thank you all for your responses.
You've convinced me I'll keep the spark plugs in metric
In fact, I thought to convert the head to more easily find spark plugs, when I order parts from Snyder's, and get the spark plugs perfectly adapted to the Model T.
That said, I can also find spark plugs metric in France, but I do not know what is best for Ford.
So I will experiment with several types of spark plugs metric to find the model that is perfectly suited to the Ford T.
Olivier, I think its good to preserve the "french touch" your car has. The suggestion of trying a tractor dealer may not be that bad. Ted even gave you some hints of types to start with.
Roger, I have never seen metric heads. It might have been a demand of the french market to have metric plugs - or it could be a misinterpretation by Ford in USA that the french requested metrics.
I doubt all the bolts and nuts in a french assembled Model T are all metric.
The Champion X is a "HOT" plug. The Champion D21 is a similar heat range. Model T's run rich and tend to carbon foul. You need to find as "HOT" a metric plug as you can.
In the microfiche records at Henry Ford, you will find reference to 'Metric' exports to Europe, which only means 18mm plugs. Until the T became popular, the American thread plugs were scarce here. I think France and UK were the main destinations, and I think it was mainly pre-War. We also had metric tyres - I think 760x90 is the T size and I believe they were standard from the Manchester factory, but I don't have the books to hand to confirm.
Anyway, I agree that D21 or equivalent is the plug to use and they are available from Tim Green http://www.gsparkplug.com/shop/catalogsearch/result/?q=d21&x=21&y=14
at £1.90each (that's 2.26 euros or $2.92). That's cheaper than Champion X.
I asume pre-War means before the "Great War" (i.e WW I). In that case it explains why I have never heard of any metric heads in Denmark as only one brass Ford with full danish history is known to survive (do not know exact year though or much else for that matter). A friend of mine have a presumably NOS 1913 engine, and that have pipethread. That engine is found in a pile of old Ford spare parts dumped on a scrapyeard and this one may have been a replacement engine.
From 1919 cars where assembled in Copenhagen and Model T's become very popular and common. Before that they where imported from Manchester or Detroit.
It would seem then that all metric heads would be "low" heads.
Olivier : If you look at: [The Car that changed the world By Bruce McCally] page 510 bottem left , that explains your metric sparkplug thread.