Has anyone installed HD8 carbs with manual choke on a Jaguar 420 sedan?
The HD8’s are fitted with an Auxilliary Start Carburretor (ASC), which is electrically operated, opening a solenoid to feed rich mixture. These are normally controlled by a thermostatic switch mounted on the water jacket of the inlet manifold. It is very simple to bypass the switch and fit a manually operated one; stops the engine running on choke needlessly. I don’t think the mainjet arrangement lends itself to being dropped like on the HS8s, but you could possibly fit the HS8 jet holder arrangement, but you may as well just fit HS8s complete.
Many. I’ve found a few on google (not that I want one, but I was looking for something related). Real chokes. Manually switching the ASC is another option but there’s a solid state temperature switch available for ~£60 as well.
I have the starting carburetor now and wired to a switch. I’m not crazy about having no air filter and once in awhile it spits gas out on shutdown.
I’ve had many mgs , Austin Healeys, Daimler V8 250 sedan and liked the manual choke. I found a set of carbs I might be able to get reasonably. Just checking to see if I should pursue them.
Only E-types HD8 have manual chokes.
All sedan HD8 do not have facility to be manually choked without great expense
HS8 are more more easily modified for manual choke than saloon HD8
I looked at HS8s but parts are impossible to find in the U.S. I can get complete carbs with choke parts on them. Just the operating linkage at the dash. I would have to be creative…
If you can buy the E-type HD8, they are the only thing that will work, but would be very expensive ?
If they are not E-type HD8, forget it.
The parts needed to modify to manual choke are very difficult to obtain and expensive.
You convert them to E-type HD8 using E-type parts
The jet adjusting lever part was/is available from Burlen, but is over 100GBP
Other parts are needed
I have never gotten my ASC to work correctly. It actually helps start the engine but it won’t run with it on, I have to immediate turn it off when the engine starts. Then the needle sticks open and I have to knock it loose for the engine to run smoothly. It now has started to leak and also spits gas on startup. It’s a nightmare. I will try to rebuild it again this year but I would investigate other carbs options. Or, depending on your climate, don’t need anything. My car will start and run without using the choke assuming it’s above ~60*F outside.
After much research, it would be expensive and labor intensive to swap out to E-type style carbs.
I will just live with the setup I have I will install a new spring on the needle and the shield kit with the tab to lock the mixture screw that I’m missing. It seemed to work ok with the toggle switch. Idle speed kept low as possible is important to prevent spitting back on shutdown.
This is a piece I modified to fit a manual choke to HS8 carbs, the XJ6 type with AED. It’s a small extension welded to the arm, which is then drilled and a small bent rod made to connect to the jet mechanism. A linkage then pulls down, lowering the jet. Worked a treat, although a bit fiddly to make. I must point out, however, that properly adjusted, the ASC works perfectly adequately. Read the contemporary roadtests. If the solenoid operates on your ASC, it’s really just a case of tuning.
This is the kit I put in my XJ6 to replace the AED. Just one carb, starts first time lowering one jet. One day I will add a fast idle.
At the moment I pedal it for about 90 seconds or so and the drive away with the choke off. Paul.
What if a timer was added to the solenoid? Turn off after 2 min,…? If that’s a complaint.
In theory, there’s no need for a timer on the standard setup ,as it’s controlled by the thermostatic switch, so it turns off the choke once the coolant reaches the correct level. Problem is, this can take some time, hence the popularity of having a manual override switch. I’ve run many a Mk2 and S Type using just such a setup and found it perfectly satisfactory. At one point I had the same symptoms mentioned previously, spitting back, hard to start etc and no amount of playing with the ASC seemed to help. Proved to be an ignition issue, points gap too small. Once the timing was set correctly, the car ran perfectly. I think the ASC setup is actually preferable to the AED used on the XJ, although do agree that the manual setup of the E Type is best.