SU's Running Rich?

[nang]

Finally got the S up and running today. Rings bearings shaft grind etc.
Trouble is she seems to be running rich at idle, sounds like it, and a bit of black smoke from exhaust. Got the jet bearings almost screwed right up. Standard BDB needles and carbs are in good condition. Had float bowl lids off and not flooding. Air cleaner off at present.
Haven't driven her yet as fuel gauge is on E and will have to go to town first and get some fuel.
Any idea's welcome.
Like Marcus I'm baffledkussed.
Tony.

[piman]

Hello Tony,

needles correctly fitted to pistons, jets centred correctly?

Alec

[WIMPUS]

Do you have a Colortune?
Then you can see straight away if she's running rich  :)

[GT6]

Check the float levels are correct, bring back some adjustment to needles by lowering it.

[yorkshire_spam]

Has it previously run on these carbs?
I'm only asking because I've seen a "Spitfire" HS4 with the wrong float bowl fitted.... leaving the fuel at the wrong height in the jet (almost flowing out the top in fact!)

[nang]

6797 wrote:

Has it previously run on these carbs?
I'm only asking because I've seen a "Spitfire" HS4 with the wrong float bowl fitted.... leaving the fuel at the wrong height in the jet (almost flowing out the top in fact!)

Carbs were not on this car previously but were on another 2500. The original ones on the S were pretty well worn so thought I'd replace. These carbs were waxstats with the 10c coin mod.
Think I'll try screwing the jet higher and see if I can get a better idle mixture. It shouldn't affect the running mixture as the needle will rise in proportion (I think) ?
Let you know tomorrow.
Tony.

[piman]

Hello Tony,

if it is not near when two full turns down then there is something else wrong.

Alec

[nang]

Seems I may have been a bit premature with my rich carb problem. Went for a 50km drive today on one our quiet country roads equipped with a 7/16 spanner for the distributor and one for the SU"s. I think a lot of what I took for black smoke was actually a bit of oil smoke.
The further I go the better it gets. I'll do so more km's tomorrow.
Ashamed to say it goes better than my TC which really surprised me.
Finally back on the road after 9 months of rebuilding.
Tony.

[nang]

Looks like I opened my mouth too soon  ;D
Spent most of the day trying to get her to run properly. Anything over 2500 rpm it's sweet and really flies. Below this engine speed it misses and hesitates.
I'm pretty sure it's a fuel problem, I've replaced everything electrical with known working units to no avail.Has Pertronix ignition and don't think this is a problem. She idles ok at 800 rpm but the exhaust beat is not good, "hunting" quite badly.
As suggested I'll get some washers on Tuesday and see if lowering the float level helps.
Tony.

[nang]

piman wrote:

Hello Tony,

if it is not near when two full turns down then there is something else wrong.

Alec

Alec, how right you are. (eek) Couldn't understand why she idled best with about 20 degrees advance, then the penny dropped.
Valve timing was out, not too sure how I managed it. So, radiator out ,timing cover off etc. Found a pair of gearwheels that were marked and used them instead of the plain ones fitted originally. Looks like setting 11 and 12 valves rocking didn't work for me.
For future reference, I turned up a couple of dummy centres for the gearwheels with a small centre drill mark in the middle, lined everything up and drew a white paint line across the lot.
Car now goes without hesitation.
Thanks everyone.
Tony. (hand)