Alan
I would have said that your distributor does not have an advance curve
that quite matches the original Lucas. I am concentrating on the
mechanical advance so any checks need to made with the vacuum
disconnected and blocked off.
The Lucas spec for a standard 100 distributor is as follows. (The 100M
is not the same.)
These figures are for the engine de-accelerating, there being a slight
variation when accelerating
These figures are distributor characteristics so they have to be doubled
if one is considering engine figures.
No advance below 325 r.p.m.
1 - 3 degrees @ 600 r.p.m.
8 - 10 degrees @ 1250 r.p.m.
15 - 17= degrees @ 1925 r.p.m.
This would give around 11 degrees @ 1500 r.p.m. on the distributor;
equating to 22 degrees @ 3000 r.p.m. on the engine. Add your 6 BTDC
making it 28 degrees. This makes your engine slightly advanced but I
would not have thought that this would give a problem.
If I recall correctly a single valve spring engine is red lined at 4200
r.p.m. and double at 4800 r.p.m. I would certainly fit double if you
can. The springs should not be a problem but you will need additional
lower cups and different top sets. It is said to be possible to change
springs without removing the head if the valves are held closed using a
fiendishly bent tool through the plug hole and the rocker shaft removed
>
>but wanted to check the max advance. At what high RPM should the advance
>be, and should I check it with the vacuum advance on or off??
>
>With advance connected, I'm getting around 32 to 35 BTDC at 3000 RPM which
>seems a bit too advanced, but wanted to check if my methodology is right.
>It is set at 6 BTDC at idle. Car starts sputtering at 4K+ RPMs, but that
>may be due to valve flutter as the A90 head only has one spring per valve...
>
--
John Harper
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