Angle of spark plugs

[A7restore]

Hi I have purchased a gauge which screws into the spark plug hole to measure the piston height before TDC. looking at it I realised that to get an accurate measurement to have the piston 5/16" before TDC I would need the angle which the spark plug hole is to calulate the correct vertical displacement.
So does anybody know what the angle is?

[Rex]

I have seen complex calculations on-line showing how to do this, but is it really necessary?
A spoke held vertically and measured at TDC and full advance is usually more than good enough.

[Joolstacho]

I don't think you need to worry about this if you use a degree wheel.
(Which makes more sense anyway).

[Billybream]

Here,s a sketch I,ve found, only guesses at angle

[Swarfcut]

  BSA Service Sheet 203 illustrates how it was done, "Stick down the hole"

 A precision measuring device, trig calculations  etc are all far too complicated for what is required, namely a spark in the right place to suit the compression ratio and the fuel octane rating, neither of which will be exactly as it came from the Factory on the day. So the published figures are for how things were back then.

 The only true test is how it performs on the road. So to get a runner, stick in the hole or degree disc is just the starting point, and certainly good enough for for sluggards like me.

 Swarfy.

[bikerboy]

I have come to the conclusion I must be the biggest bodger on here  for over 50 years now I have been putting a stick down the spark plug hole for timing and its always worked up to now. To be honest when I build an engine I do tend to measure with a depth gauge before the head goes on but if its already built a lolly stick has always worked for me.

[berger]

biker boy never mate it must be in the top stop for bodging

[BigJim]

There’s only one winner. I can’t even post the suffering I inflict on my bike to keep it running! You engineers would cast me out and need therapy! Fingers crossed the current bodges will get me to the start of the dgr.