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Post by dave1800 on Nov 27, 2011 9:33:54 GMT
Hi Tommy Just a couple more thoughts. Can you confirm which needle you are using and whether you are using the carb with the constant vacuum connection to the crankcase or the PCV. I know you have double and treble checked the needle centering but if it is very sensitive to the mixture adjustment this is one of the symptoms of a needle off centre or possibly slightly bent. Hope the storm wasn't too severe regards David I even double checked the piston and metering needle and it's centred and does not stick. And the stalling and cutting out at idle? Oh yes, it's still there! Not better at all:-( At least the float chamber doesn't overflow. And as always it's very sensitive to adjustment of the mixture. I really need to get a colortune, to see what's happening inside each cylinder. Don't have a clue at all what's going on with this car. Regards, Tommy |
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Post by tommydp on Nov 27, 2011 10:41:29 GMT
Hi Dave! The storm wasn't bad really, a lot worse on the coast with waves up to 15 meters:-)
I have the PCV system now. It works as it should with a clear rise in idle speed as I open the oil filler cap. I've tried blanking it off to se if the miss disappeared, but it doesn't.
I'm using the ZH needle, even tried two different of them. The piston falls with a clear "clunk" which is identical at all jet settings, so I just can't see how the needles can be out of centre. The piston and piston chamber are a matched pair, I even carried out a drop test on the assembly and it's all completely clean.
Regards, Tommy.
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Post by dave1800 on Nov 27, 2011 11:44:32 GMT
Ok the needle doesn't appear to be the problem. Did you try varying the ignition timing? What is the idle speed? You'll get there one day!! regards David I'm using the ZH needle, even tried two different of them. The piston falls with a clear "clunk" which is identical at all jet settings, so I just can't see how the needles can be out of centre. The piston and piston chamber are a matched pair, I even carried out a drop test on the assembly and it's all completely clean. Regards, Tommy. |
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Post by tommydp on Nov 27, 2011 23:06:20 GMT
Yes, I'm sure I'm getting there:-) My goal is to have it sorted out and totally ready by spring time:-)
I usually set the idle speed to around 750. The miss is then present as described earlier. At fast idle, above 1000, it's not that pronounced. However, I can still feel something playing up as the engine is not as smooth as it's supposed to, it's a bit shaky even at higher idle speed.
I've tried different ignition timing settings without results. Well, after all the research I can't help thinking a valve issue. The compression is fine and even though. The occasional clanking noise of the inlet valve on cylinder three really is abnormal and it follows the miss, so I regard this the most obvious diagnose I can come up with. Perhaps the valve guide is so worn it doesn't keep the valve in the straight central position all the time, preventing the valve from closing preoperly onto the seat now and then ie as the clank can be heard from the valve. I suppose a condition like this won't be as noticeable at higher revs.
Again, I could be wrong of course. However as I'm not really stressed about having it ship shape right away, I'd rather take it easy and really go into the depth of the symptom. Honestly, I can't see anything realted to the fuel or ignition systems themselves could cause the trouble now. That leaves the mechanics of the engine itself.
20 centimetres of snow here today so have concentrated on the 1967 Volvo tractor and its snowblower, preparing them for hard work in the months to come:-)
Regards, Tommy
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Post by tommydp on Dec 8, 2011 23:11:16 GMT
Hi all! I've been quite busy lately, so haven't worked on the crab for quite a while. Anyway, I got a Colourtune yesterday and wanted to test it right away. I'm still having the stalling at idle and rough running as described earlier.I've narrowed it down to what I believe is a valve issue. See previous posts.
Took it for a drive and started with the colourtune on cylinder one. Orange flame, mixture too rich. Adjusted mixture and got a nice blue, steady flame. It flashes regularly, so guess the ignition is fine. Revs were now higher and engine ran smoother, however lifting pin now suggested mixture was too lean. After a while it started missing at this setting too. Cylinder two showed same result, a steady blue flame. Cylinder three and four were different on the same setting. Itt seems the flame was paler blue, whitish, with irregular occasional orange flames. It was not possible to get a stable condition on these cylinders, when it comes to colour of the flame.
So what is this. The valve/ lifter/ pushrod noise, which is in deed abnormal, like a clear tapping, louder than the usual tick, seems to come from cylinder three. So seems there is some imbalance of some kind between the cylinders. What causes this is a real mystery to me. I can't imagine anything being wrong when it comes to the carb etc now, and there are no air leaks as far as I can see. Brake servo keeps it pressure for several hours.
Vacuum gauge as before. Around 20, irregular drop which seems to match the valve noise. This is also described earlier.
Well, still lots of time until spring:-) but time flies...
Regards, Tommy
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Post by dave1800 on Dec 9, 2011 2:14:08 GMT
Hi Tommy When using a Colourtune, I suggest adjusting the mixture so that none of the cylinders are running too lean even if that means runnning slightly rich on one or more of the others. Weak mixtures are engine killers. The siamesed inlets result in some imbalance so you would not expect them all to be identical. The orange flashes can be oil burning or a misfire probably caused by too weak a mixture if the flame is whitish. It is strange that you are getting weaker mixtures on 3 and 4, I think you need to bottom out the valve gear noise before you change the head. It may be worth checking the rockers and shaft for any damage, play or pitting on No3 cylinder. Does the noise go away or change if you put pressure on the rocker? regards David Took it for a drive and started with the colourtune on cylinder one. Orange flame, mixture too rich. Adjusted mixture and got a nice blue, steady flame. It flashes regularly, so guess the ignition is fine. Revs were now higher and engine ran smoother, however lifting pin now suggested mixture was too lean. After a while it started missing at this setting too. Cylinder two showed same result, a steady blue flame. Cylinder three and four were different on the same setting. Itt seems the flame was paler blue, whitish, with irregular occasional orange flames. It was not possible to get a stable condition on these cylinders, when it comes to colour of the flame. Well, still lots of time until spring:-) but time flies... Regards, Tommy |
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Post by Penguin45 on Dec 9, 2011 10:48:44 GMT
Rocker face may have recessed - this means that it tells the feeler gauge lies and the gap is bigger.
Chris.
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Post by threelitre on Dec 9, 2011 15:22:26 GMT
Indeed, usually on the single carb engines cylinders no 1 and 4 are the weaker ones, with one usually running hotter on all engines (not visible on the colourtune, but on the regular plugs.
Regards,
Alexander
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Post by dave1800 on Dec 10, 2011 0:55:50 GMT
Tommy I know you've checked for air leaks many times but maybe worth using soapy water to check for any leaks on the section of the inlet manifold that feed cylinders 3 and 4, something has to be causing them both to run weaker. Ifyou can't see anything, how about using another manifold to eliminate this as a cause - it would be unusual, but so are your car's symptoms. Regards David Indeed, usually on the single carb engines cylinders no 1 and 4 are the weaker ones, with one usually running hotter on all engines (not visible on the colourtune, but on the regular plugs. Regards, Alexander |
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Post by tommydp on Dec 14, 2011 11:51:12 GMT
Hi all! Haven't really done much lately. Not very keen on changing the head as I'm not sure if this is the problem. Indeed, I had the same problem on another head too, as I can see in my older posts. Also, the rocker assembly is new/ reconditioned. It had the same symptoms with other rocker shafts too.. I also tried another manifold earlier.
Suppose I'll have to find the reason for the tapping noise first. It's hard to tell if it's coming from the lifter, pushrod, rocker or the valve itself. This really is a difficult one:-)
Regards, Tommy
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Post by tommydp on Dec 14, 2011 13:49:46 GMT
Had a closer look now. Checked all valve clearances and fired her up. After a while the noise and misfire/ cutting out appeared. I'm 99 percent sure the occasional tapping noise follows the operation of a valve, and I'm also prettty sure the noise and the misfire are related. The vaccum gauge shows a drop from 20 to around 18 as the noise/ miss appears. When the noise is not present it seems the idle smooths out.
I removed the rocker cover while running, and using a thin feeler gauge between rocker and valve stem while running there's no doubt. The noise comes from the inlet valve on cylinder three. the noise is not present when running with the feeler gauge between rocker and valve stem.
So what is this then? I've no idea:-) I'm pretty sure the cam follower is not sticking. Perhaps the head has to come off anyway. Perhaps the valve/ seat has been beaten so it won't close properly all the time or something. And of course, I believe the valve guides are worn.
Regards, Tommy
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Post by kelsham on Dec 14, 2011 15:11:24 GMT
I am wondering if the cam follower is worn? Sorry but this thread is so long I cannot remember if you have examined the camshaft and followers.
I am sure you know that there were different length followers fitted to 1800 engines?
Have visually checked the rockers for indentations in the pad?
Regards Kels
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Post by tommydp on Dec 14, 2011 20:39:15 GMT
Hi Kels:-) Indeed, my threads are long.. I'm looking forward to share less frustrating threads as soon as this is sorted. I'm still optimistic though, and this car is not going out of the barn until this is fixed:-)
I have tried two sets of followers and pushrods, one set of each type, and the symptoms remain. The set of followers I used earlier was all new.
I've only used one cam, standard 1800 mk2, since my previous headaches with the 285 cam incorrectly installed by the b....y engine rebuilder. As far as the present camshaft is concerned, at least it showed no obvious sign of wear. It was the best one I had with no pitting to the lobes etc. So, I can't see the cam being the problem here but who knows?
If another head and follower/ pushrod doesn't cure it, I suppose it will have to be the cam or rather the number 3 inlet lobe. Hard to find a new standard cam I think. I see Earlpart offer reprofiled ones though. Perhaps a good quality standard MGB one will be better then.
The rocker pad is really as new, no groove etc. I suppose the noise comes from the valve seat/ valve area but can't confirm this. It's hard to tell, but it seems there is less noticeable difference when I remove plug lead three, than the other leads while engine is running. AND yes, I went back to points to perform this test:-)
Regards, Tommy
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Post by dave1800 on Dec 15, 2011 0:09:03 GMT
No need to change back from elctronic ignition to points, just connect the plug lead to a 5th plug that is well earthed, a jump start lead is handy for this.  Hi Kels:-) It's hard to tell, but it seems there is less noticeable difference when I remove plug lead three, than the other leads while engine is running. AND yes, I went back to points to perform this test:-) Regards, Tommy |
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I even double checked the piston and metering needle and it's centred and does not stick.
