Random Miss-Firing?

[Jon Tilson]

A compression test would reveal sticking valves.

Modern good fuels have a lot of stuff in that prevents carbon build up. Stick in some shell optimax or its current expensive equivalent and go for a heavy
italian tune up.....high revs blast down the nearest dual carriageway.

Ah early one....does this have strombergs? New diaphrams for both then.....

Jonners

[sprint95m]

You have said you have an early 1850,
so you have the type with the rev counter connected to the positive side of the coil.
I would either bypass the rev counter or try another (please note you cannot use the later type without altering the wiring).
It may be worth trying another ballast resistor although failure of these usually won't allow the car to run (it'll start then die
immediately).


Being early, your car has the Strombergs with temperature compensators?
These can give bother unfortunately. New compensators are over £30 each but I would try new O rings first.
1972-3 1850s have Strombergs without the compensators. These are the best type. (T2000 ones are the same save the needles).
On the underside of the Strombergs there are drain plugs (which can be removed and refitted with the carbs in situ). O-rings
are used as seals. If these leak that'll make your car difficult to start (and smell of petrol).
As Jon alluded to, the Stromberg rubber diaphragms should be replaced fairly regularly. Failure usually leaves the car underpowered?
http://www.sucarb.co.uk/CarbEssentials. ... uctId=8193



An inlet manifold air leak usually affects cylinders 3 and 4 but will only be noticeable on steep climbs or strong acceleration.
I don't think you have this problem.
The early heads have a water slot (at cyls. 3&4) which can be troublesome because the pattern gaskets are a poor/rubbish fit.
You will need to alter the holes for the mounting bolts with these gaskets (or make your own).......




Going back to your changing of the ignition components, what make of condensor did you use?
It is not unheard of for these to be faulty when new. I have had that with Intermotor.
There was a thread about four years ago concerning a similar problem on an 1850 which was cured by fitting electronic ignition,
thereby avoiding the dodgy ignition components.

[JPB]

If it is a fault with the thermal compensator circuits, I have a pair of new, as in never fitted, 150SEVs here to sell if you need these. But only as a last resort since they're reliable things (those O rings apart). They're jetted for a Dolomite but never used on either of mine as neither car had any carb faults. Thinking about it; the only O ring trouble I have had on an SEV in one of my own cars was in the one fitted to my single carb Volvo 144 and that only started to misbehave at around 338,000 miles so was probably due a holiday.

Suspect some random electrical gremlins at work.

[jedo]

will have a look next time i'm home and run through all your suggestions guys, thanks very much!! Will let you know how i get on.