The BSA A7-A10 Forum

Technical => Lucas, Electrical, Ignition => Topic started by: Ratchet Richard on 05.03. 2021 16:22

Title: A7 ignition timing
Post by: Ratchet Richard on 05.03. 2021 16:22
Hi all
In the process of rebuilding my 1958 A7.  I still have the cylinder head off and am trying to set the ignition timing.   I see that the points should open at 5/16” which I think is about 32o btdc fully advanced.
My question is around the pistons which hopefully I have attached a photo of.  I think the pistons are a higher compression ratio than standard, would this alter the ignition timing?
Thanks
Title: Re: A7 ignition timing
Post by: muskrat on 05.03. 2021 19:40
G'day Richard.
With higher compression you need to retard the timing a tad. In your case the pistons look like 7.5 or 8:1 which isn't a big increase so I'd stay with 32. Also depends on the octane of the fuel and fuel/air ratio. High octane = advance. Rich or lean mixture = advance.
If it pings under load retard the timing 1 degree.
Cheers
Title: Re: A7 ignition timing
Post by: Ratchet Richard on 11.03. 2021 17:28
Thanks for the reply muskrat, very helpful. I am having fun with this old A7, learning something knew all the time.  Regards Richard