Lancia Motor Club

I’m trying to get rid of a moment of jerkiness when for example gently joining traffic at a roundabout from low rpm. It doesn’t always happen, but it often does. I’m happy that the ignition timing is pretty well spot on.
 
I have already replaced the 47 idle jets with 49 ones and that has made a small but helpful improvement.

I’m tempted to go up to 51 or 52, but wonder if plug fouling in traffic queues is likely to be an issue due to the increase in fuel/air ratio. I could go for hotter plugs which might help if there is a problem, but that might perhaps affect things at high revs. Any thoughts welcome.

I experience a bit of the same and put it down to modern petrol. I might try bigger idle jets as well although I should get around to fitting a pair of 40 DCOE 31 Webers I have in my workshop. I may try and sell the Webers if anyone is interested and try and locate a pair of dellortos as they are simpler to fit

I am using 50 jets with 120 air and response off the line is good but I still have a vague flat spot around 3000 rpm on light throttle which feels like engine braking, may be due to air leak but is not too bad so I live with it.

Sean

Which version of PHH?

PHH E3 which originally had 52.5 jets and 200 air, I tried 55 and 57 jets but finally fitted 120 brass air sleeves and 50 jets to get closer to the old PHH settings.

Sean

I have been trawling through old threads about the solex carb and came across a post by David Wheeler in Feb 2013. He said fitting 55 idle jets made the engine pull smoothly from 1000 rpm. Do you remember that David?

That was a 1600 with 42 DDHF's iirc

The air correction jet is fixed at 120 but the emulsion tube is the one with 175/180/190/ or 200.....

I have no idea what idle jet size a 42 DDHF would have had originally fitted but I assume a 55 is larger. The point I was making was even 10 years ago people were experimenting with fitting larger idle jets to improve smooth pick up. Back in the 70's and 80's when old style 2, 3,4 & 5 * was the norm I assume people did not have this problem.

The emission carbs have different idle air bleeds, E2 is 80 E3 is 200.

Sean

I thought I would update recent experience with a pair of PHH E3's fitted to a 1400 (yes one I built). First stage was to overhaul the carburettors and get the butterflies to close. These E3s have ball bearings on the shaft so wear is minimal. You have to fully dismantle though if using an ultrasonic bath as this will ruin the small ball bearing races. Then I chose to up the main jet from 115 to 125 (anticipating more fuel requirement of the  larger engine). The engine was ran for c 200 miles but tickover was erratic and it stalled when the electric Radiator fan ran. After checking (and rechecking) synchronising of the 2 carbs, balancing the 2 channels in each carb and finely adjusting the idle mixture screws with no improvement I replaced the 52.5 pilot jets with 60. Yes it was a big jump but I was suspicious that this larger engine needed more fuel in transition. Well bingo the engine had a solid tickover (did not die when the fan kicked in) and the previous hesitation completely disappeared. As the engine is still running in (max 4000rpm) it is impossible to say if any more adjustments will be required but clear evidence that upping the pilot jet removes the hesitation during slow speed acceleration.

That’s most interesting. Did the much larger jets cause any plug fouling at low revs or tickover?

No and they wont if the idle mix can adjust within range. The car travelled back c150miles and report was no problems at all

I think most 35 PHH were originally specked with 47.5 pilot jets for the 1300 engine but now it seems a larger one now works better. I assume It must be the modern fuel.

This is a really interesting thread.

My Fulvia has hesitation under normal throttle on starting off; not great in stop-start traffic. It's fine otherwise.

When I took my car for a tune-up to a specialist a couple of years ago they did a good job ... but said there was only so much they could do as the "carburettor spindle(s) are worn". From this I'm taking it to mean this: https://www.pieces-fulvia.com/pair-of-original-shafts-for-carburettors-solex-35-phh.htm (https://www.pieces-fulvia.com/pair-of-original-shafts-for-carburettors-solex-35-phh.htm)

The carbs had a rebuild several years ago which was with a standard 'service kit' ... I can't recall if that would have involved new jets but I suspect so.

Is the 'worn spindles/shafts' analysis plausible and/or should the jets be the focus?

The PHHE3 is in reality not the same inside as the previous C35PHH's. It surprised me that the standard pilot had increased to 52.5 (remember this carb was c1974). I doubt the increase was anything to do with modern fuel.... That carb needed more fuel in transition possibly due to  the main jet (115) being smaller than normally fitted to PHH (120). If you look at the first iterations of the emission carbs (E1 & E2) jetting is all over the place.... I still believe if you hesitation that you can easily drive through it is worth increasing the pilot jets by say 5 or 7.5. (Regarding servicing the Solexes then only "jet" that is changed as a matter of course is the float jet).

If however there is a bigger hole in the torque curve it could be down to valve timing not being quite there....

Where do you recommend getting the jets from? I've got a spare pair of carbs which I'm planning to rebuild to hopefully cure a hesitation and it sounds like changing the jets at the same time would be logical!

Yes, definately. If either the shafts or the body through which the shaft rotates is worn there will be an air leak that will cause variable mixture and lumpy idle and various other running woes. Unfortunately in most cases it is the body that has worn so changing the shaft does not fix the problem, although it may reduce the problem slightly. The solution is to sleeve the body and reem it to make the shaft fit snugly. This is quite a tricky task to do correctly and probably best left to a machine shop or send the carbs to a specialist such as Euro Carbs.
A bodge experiment one can do is seal the shaft/body interface with a fairly lightwight silicon. If this produces a significant improvement in engine smoothness then the problem has been idenified although obviously not a permanent fix.
The so called overhaul kits do very litle apart from supplying new gaskets and maybe the float needle valve and acelerator diaphram. They certainly do not supply any new jets or needles. An easy start would be to change the pilot (slow/medium running) jets first for larger ones. How much larger? That is the question. They are about £10 each so £40 could be quite an expensive mistake, I have no wear in the spindles but get a hesitation from stationary. I have standard 47.5 jets and think I will first try 52's. 
The other common problem is that the idle mixture adjustment screws have been damaged by someone being heavy handed and "bottoming out" the tips by screwing them down hard against the stop. If this has happened it will be impossible to get the mixtures correct. Check by removing the screws (4) and examaning the tips. NOTE count the turns clockwise before resistance is felt before unscrewing. This will ensure you can put the scews back in exactly the same position but of course there is no guarantee that they had been set correctly in the first place but at least you will be putting the back in the same place. For most 35 carbs I think the correct position is about 1 1/2 turn out from fully in but this will vary with carb and pilot jet size. The correct seting can only be determined by tuning the carbs when the engine is really hot. That's a real game of fiddle and tweak.

If you are lucky to have the E3 version of the 35mm then shaft wear is unlikely due to the design having ball races supporting the shafts.

Thanks Simon - and Tim - for those helpful comments.

I'll put this down as a winter job to investigate as whilst I can 'drive around' the issue it isn't ideal and mares the driving experience a little.