John,
Where are you located Perth , Western Australia or Perth UK ?
I suggest you do a compression test , that will give you a idea as to the compression ratio . Unless the original 7.5 pistons were used again ,which is unlikely after 50 plus years , my guess is the engine is probably fitted with 8.5 pistons with material off the head & block so could be running as high as 9 - 9.5 .
I don't like running my lawnmower on 91 octane fuel besides a Bristol.
If you are in Perth WA a compromise would be a minimum of 95 octane without any ethanol. For the limited driving I do each year (most of it is spirited country runs) the extra cost of 98 is not a consideration.
Julian's curve is a good starting point but with my experience on the dyno it needs a lot more than 34 degs if you are interested in taking the revs above 3000 rpm.
---------------------------------------------------------------------------
The Lucas advance curves I have are
Part# Max Range Int Range Adv Start ECM Curve
400/1 47-50 40109 18 -19@2250 8-10@1200 300-450 369
401 51-52 40235A/B 12.5-13.5@1750 5.5-6.5@1000 600-680 471
403/5 40345A 17 - 19@2300 8-10@1450 325-450 520
These advance figures are distributor degrees & revs and must be double for equivalent in engine revs .
------------------------------------------------------------------------------
Have you had the engine running ?
I suggest you get the car restored and running on the Lucas points distributor .
You probably have more important jobs to do during the restoration that will eat up your cash.
I assume your proposed ECU is negative to earth , so consider problems with your positive to earth radio & clock if fitted.
I have been using fully adjustable Mallory twin point distributors for over 30 years without a problem . The bob weight stops are adjustable and colour coded springs of various lengths & tension are readily available to get the curve required . On my distributor testing machine they will run up to & over 6000 engine rpm and still work perfectly . The 60 year old worn or new Lucas are a different story.
I think Julian has a modified Bosch distributor that work well but are not easily adjustable if required.
To me the beauty of a points distributor is that they can be adjusted/repaired on the side of the road if there is a problem.
When your ECU packs it in you can not move ,except on the back of a tilt tray truck .
Geoff
|