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Which Spark Plug to Use in Early Low Head
Posted: Fri Oct 06, 2023 4:07 pm
by Distagon2
I have a 1912 with original engine. My question is what type of spark plug do you folks with the early Model T "low" heads run? My understanding is that the early heads had a moderately higher compression ratio. In the photo below there is a repro Champion X on the left, and an earlier Champion X original on the right. When I assess the early low head combustion chamber, I conclude that a repro Champion X would run too hot as it protrudes too far into the combustion chamber. What plugs do you run in the earlier, low cylinder heads (assume an all-stock engine setup).
Re: Which Spark Plug to Use in Early Low Head
Posted: Fri Oct 06, 2023 4:29 pm
by RajoRacer
I run straight side Champion X plugs but they're not reproduced & useable originals are few & far between !
Re: Which Spark Plug to Use in Early Low Head
Posted: Fri Oct 06, 2023 5:47 pm
by NealW
I run the repo Champion X plugs in our 1911 touring (and 1911 engine) and it runs fine.
Re: Which Spark Plug to Use in Early Low Head
Posted: Fri Oct 06, 2023 6:24 pm
by speedytinc
The compression differences in the early heads are minimal. 4-1 vs 3.9-1.
I currently run the new brass tops in a milled head with hi dome pistons. 95# compression. (6-1)
Previous was stock head & compression. Both ways ran fine.