Hi, Rob,
Rob Christopher wrote:
>
> Hi all again,
>
> I have a few questions, though, as you may have guessed.
>
> 1) My car has been converted to SU carbs (1 3/4 inch I think, not the 2
> inch) and the idle is now very low since replacing all these things (500
> rpm when warm). It was low before, 600-700, but now it dives down to
> ~300-400 any time I stop before recovering back to 500 rpm. Where do I
> adjust the idle on these to get it back to 800 rpm where it should be?
> There are three screws, one on each of the carbs attached to the linkage
> directly and a single one on an arm off the linkage and touching a cam
> type thing. I assume I turn the two nearest the carbs themselves. What
> is the other for?
The idle screws bear, directly or indirectly on the throttle spindle
actuating levers. The screw and cam arrangement is for the fast idle on
choke.
>
> 2) All my references are for ZS carbs and say the dash pots should have
> enough fluid in them "to offer resistence when the threaded part is 1/4
> inch from the top of the dash pot". In my carbs (filled with ATF I'm
> guessing from the pink colour) I get resistence when the threads are
> over an inch from the top of the dash pot. Is this correct for SU
> carbs? Should I take some of the fluid back out? Is there anything
> wrong with having too much fluid in there, I know having no fluid is
> bad.
The level should be 1/4 inch below the top of the hollow piston
rod-inner reservoir to you and me. Too high a levbel will simply blow
oil out of the vent on hard acceleration. BTW, the SU Refernce Guide
says 20SAE engine oil.
> 3) Plugs no 4, 5, and 6 were black (but not oily) when I removed them.
> 1, 2, and 3 were a nice tan colour as they should be. Where is the
> mixture adjustment on SU carbs? What do I measure to know the mixture
> is correct?
Assuming HS type carbs, the adjustment is the lower of the two nuts
surrounding the jet underneath. Anticlockwise-viewed from above-weakens
the mixture by raising the jet towards the needle. Check by pressing the
lifiting pin (or using a thin screwdriver to lift the piston). This only
needs to be a tiny amount-1/32 inch. If the speed rises and continues to
rise, it's rich, if the engine falters, it's weak. The engine speed
should rise and stay there. Use a Colourtune to check, or switch off
straight after a fast run and check the plug colour.
>
> 4) Can anyone guess the identity and /or origin of these carbs? The
> dash pot dampers have a brass hex head on them so someone at our local
> club said they are probably off of a TR4. They are NOT 2 inch SUs as
> another club member has them, and they are huge compared to mine. I'd
> like to identify mine so I can get more info on them in case I need to
> do further adjustments or I need to order parts.
Brass tops can be retro-fitted so they aren't necessarily important.
Best thing is if you have the tag(s) under the float chamber screws. The
number will probably begin AU-something and I can identify them from the
number-provided the tags are original. US Spec. TR4 has AUD 284F &284R
(=front & rear), HS6 carbs, with AUD1284QW needles.
If you don't have tag(s), try Burlen on 44+ 01722 412500, Fax: 01722
334221. They're in Salisbury, UK.
Good Luck,
Dave Hill, UK.
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