Looking for ideas and thoughts!
XK140 starts and runs very well considering it has been a bit neglected for the last 3 or 4 years. I just completed replacement of water pump, thermostat and hoses to sort out leaks and over heating… that project went well! While I was in there with radiator and everything out of the front I thought it would be a great time to service the distributor… new points, rotor, cap… kept the old condenser as the new one didn’t fit very well. Pulled the distributor from the engine and gave it a good clean and lubing, nothing seemed bad, just a bit dirty and un-oiled…
So after all this service there is a change in behavior…
Used to start from cold on half a crank, now it takes a crank and a half… still pretty good but maybe indicative of something?
Much more disturbing is a new tendency to almost stall… this did not happen prior to the distributor service… now she continues to run great, pulls strongly though the rev range and gearbox, but once warmed up, she tends to faulter and almost stall when blipping the throttle at a stop light preparing to engage 1st gear… doesn’t do this when cold…
I’ve read about problems with aftermarket rotor and caps… could this contribute? I also made my own replacement wire from points to coil block as the existing one was looking pretty sketchy…
Also did the static timing, and cleaned a regapped the plugs…
Anything here that would be heat affected?
I’m going to put the old cap and rotor back in and recheck the gap and timing…
Anything else?
Get your distributor bits from The Distributor Doctor, no where else. I had two failures from sets within a few miles purchased from SNG Barrats! NKG plugs far superior to champion now and possibly timing needs advancing a degree or two because of modern fuels. Remember fuel goes off.
My Cooper S tends to do what your car is doing when the dashpot oil gets low. I carry some in the car as it needs topping up surprisingly often, even with new carbs. What’s happening is the lack of oil allows the piston in the dashpot to lift very easily and the mixture is changed excessively when you blip the throttle.
Timing could be a degree or two off, and I suppose points gap may not be perfect, I need to locate my old dwell meter and timing light! But would that create the situation where she runs well when cold, and then develops this stumble when hot? And this is hot way past the point of the starting carb shutting off…
I did also check the dashpots while playing with the water pump and distributor… And no surprise they where dry… According to the service manual I have you are supposed to add oil to the top of the dashpot which seemed excessive to me, my past experience with Strombergs was that you fill them until the plunger hits the oil resistance with the threads about 1/4 " away from the top. When I filled the SU dashpots full I could barely lift the pistons with my finger thru the air cleaner hole, but I left them this way as that was what the manual says! When I then started to experience the stumbling I immediately suspected too much oil in the dashpots, and since she seemed to run well previously with no oil, I dumped all the oil out… But going from full to empty seems to have had no effect. I have gone thru a few tanks of gas , amazing how fast that seems to evaporate! Could be dirt in the filters in the carbs but I’m skeptical as the situation seems to have come up immediately after the distributor service and was not there before… To coincidental that it would be something else I think!