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Post by dave1800 on Jun 19, 2014 1:16:24 GMT
There have been a number of references recently to setting the rocker clearances and Tommy has noted that the workshop manual rule of nine method may give different results from using the TDC method.
I have now had a look at the BL workshop manuals I own:
AKD 4138 9th edition (1964-1972) which quotes 0.015" running for all models (apart from one of the three Mk1 cars' camshafts which is shown as 0.018")
AKD 4138 12th edition (1964-1975) which quotes 0.013" (no mention of running) for all models Mk1,11,111 and S.
AKD 3259 14th edition MGB quotes 0.015" running but various forums quote 0.013"
The valve springs, push rods and tappets were changed for Mk111 cars and I had perhaps wrongly assumed that this was the reason for the reduction of the clearance.
Note also that the 0.015" quoted in earlier manuals is the running measurement, something I have tried on the advice of a garage owner friend but I wasn't convinced of the need at the time probably because I wasn't very good at it!
Ideas anyone?
David
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Post by tommydp on Jun 24, 2014 22:15:03 GMT
Interesting, Dave!
I've also discovered similiar data.
My books all say 0,015 cold for the mk 2, even the Norwegian BL service folder, covering all BMC/ BL product. However, I've also got a Service bulletin folder, and one sheet says: Valve clearances on all 1800 engines can be set to 0,013 cold, to overcome complaints on ticking. If they knew what they were doing? Who knows, but it seems BL Norway did a good job according to the service bulletins.
I once discussed valve settings with my uncle, a mechanic for over 50 yrs and even worked at the BMC dealer. He had never set valves in other way than at TDC firing. When young, he and the other younger mechanincs at the BMC garage set the valves while running, but were strictly told not to do so by the chiefs:-)
So who knows? One thing is for sure: If using the rule of nine, as I always do, I'll make it a habit to check the settings at TDC too:-)
Tommy.
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Post by Penguin45 on Jun 24, 2014 23:29:54 GMT
For a long, long time, people have said that the "B" is a tappety engine and that the noise is to be expected and lived with. This is not strictly the case. Whilst badly set valve clearances do cause the ticking noise, it is more often caused by the cam followers becoming worn and taking just that split second to descend back onto the cam lobe, instead of staying in constant contact.
As part of the recently completed Restoration Course at Leeds City College, we spent a considerable amount of time working on an "A" series engine for a Mini, which suffers in exactly the same way. The difference after replacing the followers was quite astonishing. Steve (the tutor) also explained that this why you can get damaged camshafts, especially if the wear is on the rising lobes, rather than on the full running surface. The fractional delay leaves the follower off the lobe, then drops down with force - "tick". Ultimately, it wears through the surface hardening and you're taking the engine out......
Chris.
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Post by dave1800 on Jun 25, 2014 0:45:47 GMT
Chris, that's interesting that the noise was mainly down to the cam followers. As these are quite cheap it may be worthwhile replacing them with the engine in place. I understand that many modern oils lack ZDDP which protects the camshaft /followers so I would advise anyone replacing them to use the additive in a cam break-in solution when fitting new followers. Would you think there is any advantage /disadvantage in fitting the shorter lighter followers and longer pushrods if considering changing the followers? Tommy can advise how to replace the camshaft without taking out the engine - Mk11 cars onwards. David For a long, long time, people have said that the "B" is a tappety engine and that the noise is to be expected and lived with. This is not strictly the case. Whilst badly set valve clearances do cause the ticking noise, it is more often caused by the cam followers becoming worn and taking just that split second to descend back onto the cam lobe, instead of staying in constant contact. As part of the recently completed Restoration Course at Leeds City College, we spent a considerable amount of time working on an "A" series engine for a Mini, which suffers in exactly the same way. The difference after replacing the followers was quite astonishing. Steve (the tutor) also explained that this why you can get damaged camshafts, especially if the wear is on the rising lobes, rather than on the full running surface. The fractional delay leaves the follower off the lobe, then drops down with force - "tick". Ultimately, it wears through the surface hardening and you're taking the engine out...... Chris. |
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Post by Penguin45 on Jun 25, 2014 23:34:15 GMT
I'm not sure how the shorter followers and longer push rods would affect things. I assume that the followers would be lighter, but surely they are pushed back down by the see-saw action of the valves being pushed by the springs? The followers (Like the pushrods) are supposed to rotate freely in their channels. My understanding is that they stop doing this after a while and consequently wear in a slightly uneven fashion.
Chris.
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Post by dave1800 on Jun 26, 2014 4:04:08 GMT
Whenever I have taken out cam followers on high mileage engines they have shown an indentation which suggests as you say that they have not been rotating even though they can still turn freely. I imagine that once an indentation starts to form that becomes the natural position of engagement. The later followers with longer pushrods fitted to MGBs and MK111 1800s with the single valve springs are noticeably lighter if I recall correctly which should be better for the valve train and camshaft wear and with less inertia may return more smoothly, but my experience has been that they appear to stop rotating too and suffer similar indentations. I recall less ticking sounds from my Mk111 engines, but as previously mentioned, I adjusted the valve clearance to 13 thou on these and 15 thou on the Mk1/11 engines so cannot come to any real conclusion about the later followers. I guess the real question here is should you replace the followers or do you run a risk of faster camshaft wear if you do given the issues with some modern oils? David I'm not sure how the shorter followers and longer push rods would affect things. I assume that the followers would be lighter, but surely they are pushed back down by the see-saw action of the valves being pushed by the springs? The followers (Like the pushrods) are supposed to rotate freely in their channels. My understanding is that they stop doing this after a while and consequently wear in a slightly uneven fashion. Chris. |
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Post by broncoza on Dec 5, 2018 7:39:46 GMT
Mine is a strange problem; under load or at fast idle the tappets are quiet; but as you come off the the accelerator there is a distinct tappet noise but on what sounds like one tappet. I have read all the posts here and was thinking that perhaps the rocker arms are worn; one or all. But reading this perhaps I should be looking at followers? Any advice; it is a hell of a clatter that I have and it doesnt go away except when under power?
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Post by dave1800 on Dec 5, 2018 9:19:37 GMT
I think the first thing to establish is whether it is tappet noise. Am I right to assume it is present at normal idle as you say it goes away at fast idle? If so you can reduce the valve clearances while the engine is running by inserting a feeler gauge say 2-5 thou for each valve in turn (take care of course!). If the noise goes away this won't tell you if it is the rocker arm worn, or the tappet(s)but will tell you which valve is involved.
It shouldn't change under engine load but this is a process of elimination and I always believe in checking the easy things first!
David
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Post by broncoza on Dec 13, 2018 12:32:22 GMT
Sorry been off line for a while; nope it is the otherway round; at idle it is not too bad; accelerate and it goes away, and then when you come off the accelerator it is there with a vengeance. A sharp tapping noise. Put a stethoscope onto the cover and seems to be coming from 2 or 3 cyclinder
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Post by dave1800 on Dec 14, 2018 1:36:24 GMT
Curious. I suggest taking the rocker cover off and having a look for anything obvious such as a broken valve spring - I assume you have double valve springs as standard on UK Mk1/11 engines.
However, the valve train noise should not be affected by the engine load although there could be noise from the timing chain as the throttle is released if the tensioner has weakened.
If you have a timing light see how much the advance changes as you raise the rpm and then quickly release the throttle, remember to remove and plug the vacuum advance pipe first. This would indicate if there is play in the timing chain / tensioner. A lot of timing jitter at idle could be caused by the timing chain tension being incorrect.
Alternatively take off the rocker cover and rotate the crankshaft backwards and forwards to see how much play there is before the cam moves by observing the valves and pushrods.
Check around the engine for anything that could be knocking as the engine moves on its mountings under deceleration.
If the noise seems loudest when feathering the throttle while driving it could be rod knock, hopefully not. It is just a process of elimination, easy things first.
Hope this helps,
David
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Post by Blake on Apr 18, 2019 0:40:14 GMT
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Post by dave1800 on Apr 18, 2019 7:52:57 GMT
A good question! The earlier BMC/workshop manuals quote 0.015" while the later versions amend the figure retrospectively to 0.013" for Mk11 cars. Some MGB owners note that reducing the clearance to 0.013" often reduces power. Some advocate keeping the exhaust valve clearances at 0.015" and reducing the inlet valve clearances to 0.013". It is better to err on the side of being too loose than too tight or risk damage to the valve seats. While these engines were always fairly "tappety" there are reasons why the level increases over time. I would suggest trying to find which tappet(s) are noisy by reducing the gap temporarily on each in turn. If you are feeling brave and careful you can take off the rocker cover and insert a feeler gauge (0.02-0.04") between the rocker arm and valve with the engine running. Likely causes of noise are wear in the rocker shaft (most common), worn tappets, worn pushrods, worn camshaft lobes. Replacing the rocker shaft is fairly easy and inexpensive. David |
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