Hi Roger,
Ok, I haven't had stromberg carbs for many years now so take my thoughts with that in mind. Normally with engine problems I make a checklist to try and keep a logical approach and not dive in randomly. I check ignition first, then fuel, so I'd check the plugs before starting then go round the block to warm it up and repeat the process to look for differences when the engine is hot.
1. My first job is always to pull all the spark plugs & check that they are firing, not wet, sooty or white but the regular sandy light brown colour. That rules out no ignition (wet) too much fuel or irregular firing (sooty) or too little fuel (white). I tend to make a note of what I see and check the spark condition at each plug if there's any differences between the cylinders.
2. Ignition coils, in my experience, tend to break down at higher revs and work at idle. If yours runs ok hot and operates fine after you've hot started, then I'd put that aside for now. Likewise I'd visually check the new leads/distributor cap/rotor. In your case all should be fine, but it's still a tick in the checklist.
3. Fuel pump - you can hear my electric pump ticking so you'll know if that's working or not. As an aside, do you have a pressure regulator in the circuit ? I have a low pressure facet on my elan which is supposedly matched for carburetors but even so fitted a regulator to stop it occasionally flooding. There is some anecdotal evidence that these pumps can over power the float valves as you only need 2 - 2.5psi and too much is either a fire or problems hot starting. (too rich)
4. Pertronix - I have one as well, from what I've seen they are a go/no-go circuit although I won't rule it out as I tend to mistrust anything that can't be adjusted with a small hammer
5. Back to Fuel, which as you say, sounds a likely culprit. First check would be that there's oil in the dashpots. Secondly it seems like the idle circuit so next would be the adjustment at idle, are both carbs similar and do you have the option of checking the mixture whilst running with something like a Gunsons Colortune plug ? If so I'd check it from cold and then at normal operating temperatures to see if the temperature compensators are making any difference or sticking. If they stick open it might leave a weak mixture for hot starting ?
6. Sadly, if I'd got this far without solving it, I'd just strip the carbs down, clean & rebuild because they are simply mechanical things that you can visually check as you go. Check the diaphragm, clean the float chamber & re-set the float height, idle screws and jet height (although I've never known one to move once set). I'd probably replace the float valve & diaphragm simply to rule it out of the equation as I went back for a second loop on the ignition circuit.
Brian
