Rob,
The valve on this thermo is a flat brass disc on a ball joint as part of the solenoid armature, It is spring loaded closed (light spring force). Is there something else that should be on it?
Thanks, Mike Moore
Also, I do not understand this. I have been studying the SU drawings and discussion but I do not see anything like your picture or anything called a backfire valves. My 120 manual which promises the 140 upgrades doesn’t;t have a 140 upgrade.
Mike Niire
What Rob described- It‘s on the underside of the intake manifold and connected to the carb with a tube.
Best regards
Thomas
Thomas,
I am unable to get to the car right now, but HAD convinced myself there is no such tube on this car, I went back and looked at photos I had of the carbs before I dismantled and kitted them. I THINK I see the tube in question and I do not remember it or connecting it. Is this the large diameter threaded female fitting in the foreground??
Hi Rob,
Found the pipe which gores back to the engine, It has been over a year since I installed the carbs and had apparently totally forgotten about that connection , so much so that I drover over to see the car a little while ago, That tube is there and is connected,
I felt under the manifold and traced where it went and it seems to branch out to the two carbs, It feels awfully unmaintained so I suspect that valve is likely stuck, Where geographically is the valve located> Is ut where the large pipe branches off> Are there any photos of it available?
Thanks, Mike Moore,
Rob, should I expect to find this inside the end of the tube connecting to the manifold?
Firstly, those are HD carbs…from a 150 or later XK, and as such, I believe the choke set-up is quite different from the 140, H-style carbs. I have a HD-6 carb and manifold set-up from a saloon and that system uses individual “runners” to the intake which carry the enriched mixture during start-up. No “anti blow-back valve” as I remember on the HD system because of the small runners employed.
The 140 system requires a different intake manifold than the 150/HD system so we would need to see the whole intake system in order to offer sensible advice. Also, on the H-6 carbs, that large, threaded fitting you cited points downward, not toward the engine.
Firstly, those are HD carbs…from a 150 or later XK, and as such, I believe the choke set-up is quite different from the 140, H-style carbs. I have a HD-6 carb and manifold set-up from a saloon and that system uses individual “runners” to the intake which carry the enriched mixture during start-up. No “anti blow-back valve” as I remember on the HD system because of the small runners employed.
The 140 system requires a different intake manifold than the 150/HD system so we would need to see the whole intake system in order to offer sensible advice. Also, on the H-6 carbs, that large, threaded fitting you cited points downward, not toward the engine.
Lee,
Thanks so much,I have been told before these are H carbs, The large diameter threaded hole does point horizontally towards the engine block.
I verified the tube goes down then connects to the intake manifold, I could only feel with my hands and I THOUGHT there were 2 much smaller tubes running to the two carbs but I am not sure, Next Wednesday, I will jack it up and see Thanks, Mike M if I can remove that apparatus for inspection and cleaning,
I have a HD-6 carb and manifold set-up from a saloon and that system uses individual “runners” to the intake which carry the enriched mixture during start-up. No “anti blow-back valve” as I remember on the HD system because of the small runners employed.
Lee, I think that’s what I have. I haven’t found any pictures of it in any of there manuals, but hen I felt on the underside of the manifold, it seems as though the large pipe branched into numerous smaller diameter tubes. I was unable to get under the car to see, but my plan when I go back next week is to jack up the car and see what it takes to remove that network of tubes in order to clean them. I also read extensively the debate as to whether it’s best to use the anti0backfire valve or not. I doubt of this manifold has the feature, but I have had two fires now starting it, albeit I was using ether when they ignited… Lee , can you describe how that attaches to the manifold? Does it use brass fittings? How likely is it that those tubes are clogged up with gunk?
Thanks, Mike Moore xk150 intake man.png.pdf (183.3 KB)
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That png attachment is the same as the HD manifold set up I have…no place for an anti back fire valve that I can see. I will have to dig out my parts for closer examination.
UPDATE ON MY NON-RUNNING 140DHC
I had a suggestion to disconnect and ignore the aux carb (choke). It is in the 90’s F here in California.
I got it started on ether and "idling"at 2500 rpm. Iy was still spitting out of the AED. Paul suggested I retard the timing a bit which helped immensely and I was able to get the idle only down to 1500. Thenon a hunch, I closed off both air bleed idle screws complete ly, It made no change n idle speed (still at 1500),Although I had kitted the carbs, I did not check the throttle plate alignment, My mistaken reasoning was (1.) Parts clean up well assembled., 2. Judging by the throttle plate attachment screws, it had not been apart in a century or two (3,) The car made a trip with me about 10 years ago (4) I worried that removing the screws would cause me to break some and I had no spares. None of this excused me though from not just holding it uo tot he light to check for light leakage. Investigation also revealed the springy flex coupling had a lot of hysteresis, So I expect new screws and a new compiling Monday and we will remove the carbs and rest both throttle plates. I retarded the timing substantially but have no idea how much, Once I get the repairs made and the idle down to ca 500 (I hope) I will check it with my timing light and see where it is.
.Again, thanks for all the help, especially Ray, Paul, Dick and others…
Mike Moore
Last Wednesday and Thursday, I removed the carbs on this car (XK140, w/ XK150 carbs and likely engine also) to remedy the problem of the 1500 RPM minimumidle speed I had.
I had earlier been unable to get the idle speed any lower, even with the air bypass screw fully closed and both throttle plates closed and the AED disconnected,.The jets we’re set three turns below the bridge. I did not try to see what that effect would be to change that.
I assumed I hadn’t checked the adjustment of the throttle plats and envisioned a large ring of daylight whenever I lookd in. But to my surprise, they both looked very well aligned and any improvement I ought gave made was minimal. I examined the air bypass valves and they all looked clean and just fine, I also removed that 6 port tubing manual under the intake manifold for the red and it was very clean and clear inside since I was able to do it then,
Does anyone have suggestions as to what might be the cause for this ultra high speed idle? Week after next I expect to assemble it all and start it again.
Thanks, Mike Moore
I assume there is no hissing noise coming from your starting carb. Properly plugged the vacuum port to the xk150 brakes on the intake manifold? Checked your manifold with a vacuum gauge?
Hey Chris, Thanks! I didn’t think of the 150 having power brakes, do you know where on the intake manifold that port is located on the 150 manifold with the multiple AED inlets to the manifold??
There is hissing sometimes from AED when I am trying to start it, I have advanced the timing considerably and that helps.
If something is leaking, it would have to be leaking with fuel enriched air or it would just be a plain old vacuum leak, no?
I found my intake manifold leak on my other car by spraying carb cleaner around the intake while running, The effect was to smoothest the idle and speed it up a bit,
The vacuum port for the brakes is at the back if the inlet manifold. See yellow tape in 3.8 liter engine photo.
I also added a photo of HD carb with hisser and outlet plumbing. Assume is same as yours. Need to make sure the brass disk seats properly in the hisser when not energized.
If your idle mixture is too rich, vacuum leaks will increase idle speed. I have found regarding the spark makes for easier starting but lack of power. Getting your timing light to confirm proper timing should help.
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Chris, Thanks for the info, I will check when I see it next in a week and a half. Do you install and remove the lower carb to manifold bolts from under the car or above?
Best, Mike Moore
Morgan Hill, Ca
I would expect the starter and oil filter are in the way from the bottom. Once you get the air filter stuff out of the way, not too bad from the top. I Don’t have a lift so don’t attack from the bottom unless necessary.
Same here almost-layingon my back in a driveway. Whenever I have it uo on jack stands I think I need to have it down, then when I have it down I think I shojuld have had it up. Since I now have it down , I’m thinking it night be easier …Thanks Chris,
BACK TO THE 140DHC
Today I finally got back to work on this car, I had it started but it had an ungodly high idle speed plus backfiring through the AED etc, I removed both (rebuilt) carbs and checked the throttle plates to make sure they were closing fully. I noticed the flex coupling was in terrible shape so we bought all new parts there which I installed.I am not satisfied with how well the throttle plates close but am satisfied I am unable to do much better (I tried and have not had that problem with my E Type). The throttle works much better and I m hoping the was a source of my 2500 rpm idle speed!
I also removed the AED manifold which fed into the bottom of this apparent XK-150 intake manifolds. All passageways were clear and I replace the two pieces of “rubber” hose which connect the parts, This morning I finally got the carbs back in and all connected EXCEPT I am missing a wire which connects to the AED solenoid. I have the wire which goes back to the dash and has 12v. The other wire must be the ground wire. I’m unable to identify just where the other end normally would connect and would like to know where the most tidy ground attachment point is. If anyone can tell me, I’d be grateful, v/r Mike Moore
The other wire on the aed lands on the otter switch that detects water temp. The switch opens when hot so the aed looses its ground and deenergizes.