----- Original Message -----
From: "JJ&A" <w7ls@blarg.net>
To: "Military Vehicles Mailing List" <mil-veh@mil-veh.org>
Sent: Monday, July 16, 2001 1:27 AM
Subject: [MV] Tuning Saracen carbureator. Tips, anyone?
> Our Saracen has less power, now that we rebuilt the carb. That kinda
> makes no sense to me, unless it had been tuned to account for being
> clogged, somehow. Now that it is unclogged, the tuning ratios would be
> different, I suppose.
> ` I'd appreciate any tuning tips from people that have done this
> operation on this vehicle. Thanks. Jim
>
The 40 NNIP Solex fitted to a B80 is a fixed jet carburettor with only idle
mixture and throttle stop adjustment available, all other systems are fixed
and "untunable".
It is quite possible to mis-assemble the instrument though, damage a fine
gasket or tear an accelerator pump diaphragm by not flexing it before
clamping its cover.
It has three filters, one in the inlet banjo and one below each accelerator
pump.
I would minutely re-check the device for assembly faults and correct gasket
placement, plus the fuel line felt filter element which can hide a multitude
of sins, water and rust, service the oil bath filters and replace the oil to
the level mark.
It is possible a choked carburettor was hiding other faults, this engine
uses a twin point ignition system, it is entirely impossible to set the
critical 45 deg angle between the points without removal and the use of a
specially made jig (simple). Each set of points fires a cylinder in turn
AND acts alternately as a dwell angle extension system for its mate, if the
internal angle setting is wrong 4 cylinders will be mis-timed relative to
the other four. You will note it is an 8 cylinder engine with a 4 lobe
distributor cam and can be likened to a pair of 4 cylinder distributors on a
common body firing 45 deg apart.
It is also critical that B Range engines are statically timed between 0 deg
and 2 deg AFTER TDC. This cannot be done except with a static timing light
as the design intentionally advances the ignition at idle speed, the setting
allows for hand cranking in an emergency with no danger of a kick back. Any
attempt to set the distributor with the engine running at idle by ear or
with a strobe is a guaranteed disaster.
Check also that the ballast resistors are intact and that half the battery
voltage (engine static) is actually available at the coil with one or the
other set of points closed.
Bad rotor arms and distributor caps can also give every indication of a carb
fault whilst allowing the engine to start easily having the ignition boost
start with the ballast resistors by-passed during cranking.
The platinum screened plugs are readily fouled and will not self-clean no
matter what the general hype about these types may lead you to believe, it
is quite difficult to hear that one or two may be intermittently firing and
if it has run rich during previous work then some fouling is quite possible.
Have the screen unions already slackened and remove each lead in turn at
idle noting any change in revs or note, there is little danger of a HT shock
as the leads are screened and grounded through their sheaths.
Have the plugs grit blasted to clean and only then disassemble them to
ensure no grit remains, do not ever wire brush the disassembled plug with
steel or brass brushes, the platinum will either be compromised or you will
leave metallic traces in the centre insulator causing tracking. Re-set to
15 thou.
We assume the rest of the engine is in acceptable order.
Richard
Southampton - England
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