Hi Graham

Thank you very much for the info - much appreciated.


MJ

Graham W wrote in message ...
M.J. wrote:
I'm trying to find ignition timing settings for a marinised BMC 803
engine (as fitted to the early minis/minors and Austin A35s).

The 803cc APHM is an even smaller version of the A series than the 848cc
motor fitted to the early Minis. It was fitted to Minors from about 1953
to 1957 when it was replaced with the 948cc version which has a larger
bore. The smallest Mini motor is the 848cc which is a 948cc with a
shorter stroke.

The
engine has been recently overhauled and I believe it has been fitted
with an unleaded cylinder head so would it be necesssary to retard the
ignition to run on u/l fuel?

Unlikely.

The unleaded cylinder head would basically have hardened valve seats to
prevent valve recession. I would think modern unleaded has at least the
same octane as 1953 British petrol! In practice I would treat the
recommended ignition timing as no more than a starting point. With
modern fuels and after a rebuild you may get away with considerably
advanced timing. Listen for pinging.

I also need contact breaker and plug gap settings. Could anybody
please assist?

Ignition timing: 2 deg before top dead centre, 3/32" or 2.4mm at the
perephery of the crankshaft pully.

Contact breaker gap: 0.010 to 0.012 in. (0.25 to 0.30mm)
Contact breaker gap (high lift cam): 0.014 to 0.016 in. (0.36 to 0.40mm)
(it's probably the latter)

Spark plugs: Champion N5 (was code NA8), 14mm, 3/4" reach,
Plug gap: 0.025 in., 0.64mm.

Condenser capacity: 0.2mf
Vacuum advance 7 to 9 deg
Centrifugal advance 17 to 19 deg, starts 400 to 650RPM.

The distributor is probably a Lucas 25D4 also used in many early Minis,
Minors, Hillmans, etc. Later (up to at least 1980ish) Mini distributors
are probably interchangeable for fit. There are many many different
advance curves, and with modern fuels it's anyone's guess what would be
optimum. Since you probably use the motor to idle or to go at hull
speed, I'd set up the timing for best performance at hull speed.

As you have probably worked out, I've got a Minor workshop manual here,
so if there's anything else you'd like to know from it, just ask, or
contact your local Minor specialist.

Graham.

Remember to adjust my email address slightly...