I'll do my best to be as eloquent (and succinct) as possible, but I feel that each of the following posts can benefit from comment. I'm going to be
breaking in to each quoted post for clarity, rather than list my observations at the end; hope that makes everything clearer...
My mk I on Webers has from one day to the next become hard to start from cold. Warm starting and normal running is fine.
This should not be the case; I can get my BN6 (29D engine, should be same as yours) to light up first time/every time. I do not have the auxiliary starting circuits connected (aka "choke" though Webers don't use a
strangler-type, as the moniker implies) but by waiting until the fuel pump has fully filled the float bowls, and giving it two to three (2-3)
full strokes on the accelerator pedal__
SLOWLY, allowing the pump jets to fully discharge__and it lights off on the FIRST activation of the starter (while not
instantaneous, but certainly within just a few seconds, undoubtedly helped by its gear-reduction starter). Though it's not a practice I endorse, if I
had to, I could drive off immediately with the engine stone cold; now it couldn't process a
bootfull of throttle opening, but well it's mannered enough to toodle out of the subdivision.
Its always been cantankerous but normally starts after a couple of go's with a bit of sputtering and popping.
Now it sort of starts and runs on a couple of cylinders at about 400/500 rpm but never really catches. Eventually after quite a few try's, it will clear and once warm it's runs like its usual self though it has never idled well but that's Webers.
That's indicative of too lean a mixture, assuming the actual settings (ALL 68 variables) are matched to your requirements. If it still does that after following the starting process outlined above, then there is still work to be done (best by someone that possesses an acute skill to tuning an engine, if not experience specific to the Webers themselves.
Webers will most assuredly idle, even on a freshly started from cold engine, and all the moreso on a stinking hot one.
Its got fuel (I also pull the plugs after one attempt and they were slightly damp but not wet/fouled). Its firing on all cylinders spark wise. Fresh points and condenser with timing set 500 km ago. And again one warm it pulls like a train.
You clarifed this as the culprit later, but as soon as I saw this, the first thing I thought of was the point's rub-block wearing down__it's an age-old problem, and I used to always set customer's Healeys a few thousands wide to compensate (otherwise, we'd get The Phone Call...). I'll elaborate more on the ignition, and what I recommend to cure that once and for all.
Only thing that was changed was to increase the idle rpm to smooth that out but I've now redone that after taking it for very hard run to make sure all was "cleared" out.
I've not re-checked the timing but other than that I'm not sure what to try next.
Any thoughts?
You didn't say what you changed; may I ask?
I've not re-checked the timing but other than that I'm not sure what to try next.
Any thoughts?
Got some good SU's---
Now look, you!
Suggest these sites:
https://www.carburetion.com/Weber/adjust.htm
https://www.redlineweber.com/html/Tech/carburetor_set_up_and_lean_best_.htm
Here - scroll down to AH settings:
https://www.boiperformance.com.au/weber-tuning--jettings
Some of the weber users here might comment, but getting 3-6 colortunes might be a pretty good way of getting the idle mixture screws all the same.
Here in Southern California we have a guy who travels around tuning webers by ear who does a terrific job. Might there be someone like that down the hill in Northern Italy?
Some good links, thanks for posting those up; I plan to go through and check them out more thoroughly, once I get this monstrous editing job done!
Rather than waste your money on colortunes (I have one that hasn't been out of the box in over three (>3) decades, get yourself an IR Thermometer Gun, and point it at the headers; way more telling, and you can do that in any light! If you're still running the OE cast-iron exhaust manifolds, the results will be far from instantaneous, but with steel-tube headers__which you should be using with Webers anyway__you can see a tremendously fast response to changes. It's the only way to go when setting the idle mixture strength!
You'd certainly expect there'd be a Weber specialist in Italy, wouldn't you?
The thing with Webers is to set them and forget them. My Webers were tuned on a rolling road 3 years ago and I haven't touched them since. The worst thing you can do is start fiddling with them.
DING, DING DING!! We have a winner!
Indeed, once they've been properly set, which I'm questioning on Mr. Swiss Toni's application, leave them alone. There are exceptions though, like when moving from Louisiana to Ohio (required the slightest leaning out of the mixture strength) and again when moving from Ohio to Florida (just the opposite). I don't know if it was a variation in gasoline formulations, or the sea-level (which was really only a few hundred feet). Since everywhere I've lived with the Healey since putting the 45 DCOEs on it, in 1986, has been very flat, I don't know how well it would tolerate a severe change in elevation, like driving over a mountain's pass.
Double check all the ignition items first, if that doesn't work it might be time to visit a rolling road. I assume you give the accelerator three or four prods before attempting to start. Even when correctly set up they will cough and splutter on initial start up as you described.
Again, along the same thinking as myself. I would keep the
prodding to the absolute minimum required though, only as many pumps as it takes to get the engine running (mine will almost always suffice with 2 full strokes) as you will dilute the oil with fuel. I have been relying on engine oil analysis for nearly forty (<40) years, and one of the early sample results returned on the Healey, once it was back on the road in Ohio, showed a measurable amount of fuel dilution in the oil. After that, I cut from three (3) down to two (2) full strokes (or prods
); one (1) was just not enough.
Thanks Steve for the links, problem solved.
The troubleshooting matrix pointed as well to timing as a hard starting issue, it turn out the points gap had closed down.
Resetting the gap and it starts and after resetting the timing idles ok.
The next step is to find out why the gap closed down as all was set correctly (dwell was checked at points replacement) and everything was tight.
I suspect that there is various wear issues in the distributor (I feel a new thread coming on).
Yep, as I suspected, and confirmed earlier.
Your distributor may well have wear in it, put the rub-block wearing down during the first several hundred miles is very common (you did put a
light smear of lube on the distributor cam, right?) and why I set them .002 to .003" wider than spec, so say at .018-.019".
You just experienced one of the most popular cliches about the majority of carburettor problems being electrical though!
I am a tuner, understanding the engine's requirements, and recognizing what it needs when it doesn't run right, and the steps to take to improve the condition (sometimes, you can only treat the symptoms, but eventually, you get to the root cause). My engine has been set up to handle the increased carburation; hotter cam, gas-flowed head, balanced, exhaust headers. But I still experienced it loading up on fuel at low engine speeds__particularly if I got stuck in stop & go traffic. No amount of blipping the throttle,
clearing its throat, would suffice.
Too much fuel or too little spark? Well, I could not run the idle jets any smaller without constant backfiring, so it was as lean as it could go, so the fuel had to be burnt! Firts course of action was to fit a Mallory dual-point distributor and their hot coil. This was a marked improvement, but there was still issues, though fuel accumulation was to a much less degree. So at least I was seeing a change in the right direction!
The last step I took (to date, at least) was to fit an MSD Ignition system. The multiple-spark discharge ensures that all the fuel is burnt at extremely low engine rpms. As the revs climb and dwell time is reduced, so is the number of sparks, but they're not needed at high rpm anyway. My problem was solved, and I could now enter the car in a Mardi Gras Parade,
if I wanted to!
Glad you got your hard-starting resolved, but I think your Webers could still benefit from the attention of a specialist, based on your statements above.
I'll leave you with this:
Hey there Guest!
but were afraid to ask: 
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