what setting for ignition timing

[paulr]

hi all,

thanks for everyones advice so far- new question.

the engine in Ruby is a standard 1275 single su but no engine number so not entirely sure of age or exact spec -haynes manual gives a variety of ignition timing settings depending on age and spec of engine - most common seems to be 11degrees BTDC but for 1985 on standard compression engines it quotes 7-9 degrees btdc ,

is there a way of telling which it should be other than by setting it at one - trying it - and if it runs fine leaving well alone ?


thanks

[Hans Efde]

Just forget what's in the Haynes and do it by feel and sound. It is amazing how the engine will change its behaviour when you start advancing the timing. A dull engine can suddenly become a real screamer. According to a book from Des Hamill about power tuning the A-serie he describes that the total maximum advance must be 33-35 degrees BTDC. It depends on which distributor you have what the initial timing will be. He advises to start with 15 degrees at 1300rpm idle and test it. If the engine "pinks" under full throttle, go 2 degrees back etc.
This is consistent what I had on my turbo engine. I had a idle advance of about 25 degrees because of the low compression pistons and the dialled in 14 psi turbo pressure. The special turbo distributor would only advance 6 degrees because of the heavy springs and no vacuum. Funny bit is that the previous owner had spent thousands of pounds on this engine to get maximum power and still had just 5 degr BTDC dialled in according to the Haynes. He never was able to use to the full power potential of this engine. When I had sorted it out, acceleration was about doubled.