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Post by dave1800 on Sept 27, 2011 13:15:02 GMT
It's really good to hear the car is running well now. Looking at the difference between the TW and ZH needles there is only around 0.001" max difference in the mid range (ZH being richer). I am surprised it is this sensitive, and is useful information for my project, thanks. It makes me wonder how quicly the biased needles and jets wear in the Mk111 cars so negating any of the pollution benefits, I must admit changed mine back to the non contact variety! Regards David Anyway, it seems logical, as the final trouble I had was in the mid range, where the TW is weaker. Typically it would miss on acceleration, and then catch up again. It now performs fabulously throughout the range. A Colourtune will be ordered! Regards, Tommy:-) |
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Post by threelitre on Sept 28, 2011 6:02:11 GMT
Confused? That's why I am still working on a system to measure carb piston lift in situ while driving in conjunction with a wideband sensor so that I can modify the needle profile to what is needed. I will have to try it out here on a Hitachi - SU look alike - carb on a Nissan "A" series clone but the principles should apply. Not confused.... I have a Innovate WB sensor and handheld thing here. So far I have not bothered to read out MAP or rpm at the same time - but have thought hard if it was possible to use a TPS to measure the carb piston movement  You can see if the spring is right by just accelerating the engine, as it should lift most of the way to the top, but to see where the needle is rich or weak the above would be the perfect solution. David Vizard once described something similar: Use the measuring pins from the SU toolkit and (a pair of) colortune(s), jack up the front of the car and get a mate to rev it and change the load via the brakes... Alexander |
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Post by dave1800 on Sept 28, 2011 11:18:18 GMT
My thinking is: (a) measure the vacuum (with a MAP sensor) above the piston in the carb. These readings can then be equated to specific piston lifts (this can be checked with the car stationary using a wire indicator on top of the piston etc such as sold by MGB specialists). (b) using a WB sensor and the vacuum readings together should indicate which parts of the needle require to be richer or weaker under actual driving conditions. This relies on the fact that the SU works on a constant depression ie vacuum basis, so the amount the piston rises should be proportional to the pressure difference above and below the piston. (I understand the spring is designed to operate in a linear way over the range it operates so it shouldn't be a major problem). I would welcome any thoughts as to whether I am on the right lines or if my thinking is flawed. regards David Not confused.... I have a Innovate WB sensor and handheld thing here. So far I have not bothered to read out MAP or rpm at the same time - but have thought hard if it was possible to use a TPS to measure the carb piston movement You can see if the spring is right by just accelerating the engine, as it should lift most of the way to the top, but to see where the needle is rich or weak the above would be the perfect solution. David Vizard once described something similar: Use the measuring pins from the SU toolkit and (a pair of) colortune(s), jack up the front of the car and get a mate to rev it and change the load via the brakes... Alexander |
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Post by threelitre on Sept 28, 2011 22:17:31 GMT
Yes, that should work! And apart from sacrificing one dashpot (per carb-type) it does not cost a lot and is easy to implement. When not used anymore the bore can simply be plugged - I like that idea and will possibly try this once I get my hand on a used MAP sensor...
Regards,
Alexander
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Post by tommydp on Oct 8, 2011 5:43:17 GMT
Hi all! It's been a while, so time for an update. I've used the 1800 every day and will continue to do that until the snow, or rather the salt on roads, arrives:-)
The car still performs well most of the time, sometimes it will still misfire like it used to, but not as bad or often as it used to.
As mentioned earlier I've been a bit concerned about the oil in number one cylinder and the fouling of the spark plug, especially after long periods of idle. There's also been some blue smoke after deceleration. The other cylinders and plugs are dry and fine. Well, yesterday I decided to have a closer look at the number one cylinder's inlet valve and possibly put an umbrella type oil seal on this valve's guide.
I managed to do this with the cylinder head in place. With the piston at the bottom i filled the cylinder with a soft rope, through the spark plug hole. I then turned the engine to move the piston up on the firing stroke until the rope made contact with the valves, keeping them in the closed position.
I pushed the inlet valve's rocker to the left and using a long bar from under the rocker shaft, I easily compressed and released the valve springs. I put a rubber hose on to the bar, to protect the rocker shaft when compressing.
The rope did the job and the valve remained i close position. There must be excessive clearance between the valve guide and stem on this valve. I could clearly see the gap between the stem and guide and there's quite a bit of sideways movement.
Anyway, not up for a head change now, so I installed the extra oil seal to the valve guide. I even got it back together again quite easily, pressing the bar with my knee while fiddling with the other oil seal ring and valve cotters:-)
Well, it made some change as the piston top is now dry soothy as the others, and the plug appears fine after idle too.
I suppose I'll get a proper, reconditioned head during the winter. But this will do for now:-)
Regards, Tommy:-)
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Post by dave1800 on Oct 10, 2011 10:06:41 GMT
Hi Tommy You did well changing the valve seal in situ. It does sound as though there is a lot of play in the one valve stem, do you have any idea why that is the case? I see on the Peter Burgess website they are offering new cylinder head castings at £360, but maybe you only need new valve guides / valves? www.mgcars.org.uk/peterburgess/page12.htmlWhile you are facing the cold and snow in a few weeks, I am looking forward to the winter here as it means I can work outside for more than half an hour as the temperature will be closer to 27C than 37C. We have had terrible floods here, so I have been learning all about sandbags and pumps. The sandbags are unbelievably heavy once they get wet. Regards David |
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Post by tommydp on Oct 10, 2011 12:23:52 GMT
Thanks, Dave! At least my work on the car now is making it better and better:-)
Putting that oil seal on the obviously worn valve/ guide has really made it even better, it idles beautifully and pulls very well in deed. I wonder if the guide is so worn it lets unmetered air in, as it now responds better to the lifting pin test too. There's the correct slight increase then fall of the rpm. I've never managed this on a regular basis before. It's always been too lean.
My uncle tried it again, and was convinced it never felt as strong and fast when my grandparents drove it. He was really amazed by the performance, as well as the brakes which he means are better than some modern cars:-)
I will indeed get a cylinder head from Mr Burgess, during this winter.
Finally, the car has now totally matched components for the mk 2, and I'm sure this is critical. That is the correct cam, the ZH needle and the 41234 25 d distributor. I'm using the Lucas sports coil. It does not get abnormally hot any more.
Enjoy the temperatures you're having, I'm quite envious.. The mountains are covered with snow here, so I guess it's just a matter of days:-) I'm putting studded tyres on the crab, to have it as a back up. My Peugeot is the worst car for winter use ever made, even beats the 1,8 Marina and Granada:-)
Regards, Tommy:-)
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Post by dave1800 on Oct 11, 2011 1:31:33 GMT
Back in the mid 60s when I first drove a Landcrab we soon got into the habit of carefully watching the car behind when applying the brakes. You can't imagine how poor the brakes were on some cars back then in comparison. Looks as though you have everything sorted apart from the cylinder head now. regards David My uncle tried it again, and was convinced it never felt as strong and fast when my grandparents drove it. He was really amazed by the performance, as well as the brakes which he means are better than some modern cars:-) |
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