Hi Guys , I’m fitting a new distributor to my extra 12 series one. I have located the timing mark on the bottom pulley however, looking through the plug hole on cylinder 1A does not tell me whether I am at TDC compression stroke or TDC on exhaust stroke. Strangely the workshop manual does suggest that it is possible to determine this by looking through the spark plug hole. I assume they think the valves are visible when open. Can I do this by reference to another cylinders position ? Not quite sure what I am missing here.
Never worked on a V12 so not sure if this is going to help.
Remove A1 spark plug and place thumb over the plug hole and get someone to turn the crank with a socket you will feel compression building as the engine comes up to TDC.
Thank you Robin. I was thinking that as a back stop but don’t have anyone to hand who can help with that sort of work. I did once hear about TDC whistles but don’t have one either. It’s just odd the manual states that one can observe TDC , sure you can but not on compression stroke specifically.
Put a bit of duct tape over the 1a (front right) spark plug hole and turn the engine over forwards. When you are on the compression stroke, the tape will bulge outwards and then blow out.
That’s a good idea. Thank you Marek. Actually looking at a photo of a V12 head it does look like one would be able to see a valve so I may be on TDC compression stroke now. I will have another look tomorrow thank you