36 forum posts
I am currently machining the cylinder head for my ET Westbury Wyvern. The build notes say to use a M10x1 thread for the spark plug and not the 3/8x24 as per the drawings. I guess thats because modern plugs are metric. I will be running on petrol so my question is are there any recommendations for the plug. I want to leave or remove enough material so the tip is in the correct position. I will want the plug in hand before I continue with that feature. Also what is the correct position for the tip. This is my first IC engine so sorry for the beginner sounding questions.
184 forum posts
The NGK CM-6 plug is often used for engines of that sort of size (it is M10 x 1 thread).
I used one for my little (20mm bore) hit and miss engine:
They are readily available and reasonably inexpensive.
In the absence of any information to the contrary, I'd aim for the end of the plug body to be ~flush with the inside of the head, provided that nothing comes too close to the electrodes in that configuration.
Edited By Andy_G on 23/06/2022 10:05:01
|Roderick Jenkins||23/06/2022 10:08:37|
2201 forum posts
+1 for everything Andy says. That's what I used on my Wyvern it works ok.
23022 forum posts
Same here I use the NGK CM-6 on the larger engines.
I've done engines where the plug is a long way removed from the cylinder in separate valve blocks but they still work OK
|noel shelley||23/06/2022 10:24:38|
|1435 forum posts|
The main thing is that nothing hits, I once came across an engine that would not run ! The owner had put a long reach plug in and the gap was closed as the piston hit it ! Shorter plug ran fine ! Measure piston height and any head clearance and go from there. Plug position will dictate combustion/flame fromt.. If your near me I could lend you a 10mx1 tap. Good luck. Noel.
36 forum posts
Thank you for all the excellent replies. Just what I needed to know. I left the plug entry point a bit high so I can take a bit off to get the plug position right when I get one to install. Coming from steam to IC is challenging so I may have further beginners questions when it come to timing and making a spark. Ordered the tap today. M10x1.
Edited By NR67 on 23/06/2022 21:41:52
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