Manual Choke ???

[jagman723]

My 3.8 runs well enough once warmed through, but can be - no IS - a real 8*99er to get from cold to that point. I have the standard AED set up which I bought new from Burlen ages ago and at the same time I refurbed the carbs so all should be in order, well relatively.

In this cold spell we've had of late I have been musing over the possibility of converting to some form of manually operated choke mechanism to give me a degree of control during the warm up phase.

Does anyone have a magic answer or otherwise some advice on how I could proceed please?

[smiffy]

Good evening Jagman
Presumably the engine starts OK in the first place? By AED I assume you mean the starter carburettor that goes with the SU HD6s? I also assume that you have set up the starter carburettor as per the manual. Two ways I can think of to sort this, though there are probably others. First thing to try is using a temporary switch instead of the thermo switch (so-called Otter switch), which will effectively give you manual control over the starter carburettor. If the car then behaves, replace the Otter switch. If you want a proper manual choke, you could use a pair of HS6 carbs from, say, a 240 or an MGB, as these have a choke lever. I would start with the basics, and check the set-up of your starter carburettor.
Best wishes, David

[jagman723]

Thanks for that Smiffy and yes the AED with HD6's.

Well, I think I set the AED up correctly as I followed the manual and the unit, as I said, was bought new as part of my restoration in the first place. Again the otter switch was new at the time so I hoped it would all work OK - but no and I have kind of got fed up with it hence the manual choke thought now.

I like the idea of the later manual choke carbs as long as they are a straightforward fit on my existing manifold (?) though as you mentioned HS carbs I seem to recall something from the dim and distant past about 2" HS8's fitting too.

I'm sure that MGBs let alone the 240 would be set up differently with the HS6's do you know what needles, etc. I'd need for my 3.8 or where I could get help on that please?

[smiffy]

Hi Jagman
The HS6 should be a straight swap - I lied about the MGB though, as it had HS4s, it was the MGC that had HS6. Fitting the 2" (HD/HS carbs may need a change of manifold - I'm not sure on this one, but they were fitted to the XJ6. According to my SU Tuning Manual, the TL needle will work with most 1.75" SU carbs on the any of the XK engine range up to 3.8 L. If you have an oil bath air cleaner, the CI needle might be better, but there is very little in it (I'll send you a copy of the Jaguar application pages from the SU manual and my graph of the SU needles fitted to Jags if you PM me your address).
Does your engine run rich or lean when warming up? You should be able to get the AED working; you will either have too much fuel or too little while it is in circuit if the engine won't behave, but I understand you losing interest if it does not respond to your ministrations.
I'm soon to fit a pair of HD6s to my 2.4 L Mk2 (when I've got them cleaned up and rebuilt) so I'll keep you posted.
Best wishes, David

[velosolex50]

I had loads of problems with the AED on my SU conversion 2.4. Cured by converting to LPG, starts from cold on gas & runs perfectly. Now replaced the carbs with NOS SU HIF (from an Indian rover SD1)without any starting device, and it runs really well. Just have to make sure I'm not caught with no gas & a cold engine......

[jagman723]

Thanks, I don't think I'll be converting to gas, but the later model carbs may well be worth investigating.

[jagman723]

By the way do you know the HIF number and are they a straight fit to the existing manifold?

[simon4253]

su hs carbs are no worse than hif carbs as you do at least have a proper float bowl which you can get at in situ unlike an hif carb which requires contortionism and still blocks and floods just like an hs or hd carb especially if not used regularly! A carefully built hs carb will work great. Tried hif carbs on jags,and rover and nothing but aggro and mixture screw was almost impossible to get at with air cleaner on with hif so go modern by all means but don.t expect miracles