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Post by Andyberg on Jun 15, 2020 9:13:43 GMT
I expect push rods might be an easy to source part. Couldn't you get βQβ to knock you some special strengthened items up whilst he is furloughed?π Perhaps lathed from unicorn horn or something? π
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Post by Isambard Kingdom Brunel on Jun 15, 2020 10:04:09 GMT
If you suspect that they are bent, roll them on a flat surface. The can be straightened, they are only flame hardened at the ends. Be very careful when lifting them out. Give them a twist as you slowly lift. If the cam follower sticks on the end with the oil it is possible to lift it out of the block which will then necessitate you removing the side cover plate to put it back in. Ask how I know that?
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Post by Deleted on Jun 15, 2020 11:35:11 GMT
I expect push rods might be an easy to source part. Couldn't you get Β βQβ to knock you some special strengthened items up whilst he is furloughed?π Perhaps lathed from unicorn horn or something? π He isn't furloughed.
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Post by Deleted on Jun 15, 2020 11:37:03 GMT
If you suspect that they are bent, roll them on a flat surface. The can be straightened, they are only flame hardened at the ends. Be very careful when lifting them out. Give them a twist as you slowly lift. If the cam follower sticks on the end with the oil it is possible to lift it out of the block which will then necessitate you removing the side cover plate to put it back in. Ask how I know that? Good advice thanks. I did wonder about the follower as I know it's there but like I said never really did much of this hands on thing as I usually get it wrong
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Post by Deleted on Jun 17, 2020 11:08:35 GMT
With regard to the excessively loose tappets/valve clearances you found on the 'knocking' engine, ] I've been thinking about this. There were two or 3 with excessive clearance. The others were reasonable. Boat was laid up ashore for 3 years then someone got the engines going (before I bought the boat) Tall vertical exhaust stacks. I only found one exhaust cap when I bought the boat. So some rain could have got into the exhaust system on the starboard engine. Not a lot of water but something. It's a custom made stainless steel dry exhaust silencer box on each engine. So I reckon this caused some condensation problems and perhaps a couple seized valves in open position. Then when engine started pushrods engaged incorrectly and bent. So I think I will find 3 bent pushrods when I have a look at it next weekend. Hoping it's not more serious but the excellent starting seems to rule out any bent valves. Which is good. And the rockers themselves look ok. Original owner/builder had placed an oil squirt can beside each engine but not everyone would know that it is sensible to oil the rockers manually after a long period of no use. Anyway that's just my theory. Will find out before long. Geyser I bought boat off had it for 12 years (1985 boat) however the engines only have around 1600 hours on so I don't think he actually used it much. Which is good in theory but comes with its own potential problems. The custom made coal fire had a couple of inches of water in it when I bought the boat as the chimney had not been capped... Quite upsetting but it isn't wrecked fortunately and all of the flue components are stainless steel. There is actually a stainless plate which bolts over the flue collar with a gasket but it was left in a drawer rather than being used to seal the fire up when decommissioned..
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Post by Isambard Kingdom Brunel on Jun 17, 2020 12:47:48 GMT
Water down the exhaust is the frequent cause of valve stems rusting. On the valves that are left partially open this will lead to them not closing under spring pressure when the camshaft is turned. On a stopped engine there are generally 3 valves open.......................... But fortunately on the BMC 1.5D the valves are not inclined with respect to the piston crowns which are flat. So on cranking the rising piston knocks the stuck valves closed, imposing a shock load on the rockers and pushrods. It is rare in my experience to get a bent valve. I have found that usually it is the rocker that gets bent, the pushrods being long and hence slightly flexible, less likely so. I would inspect the rockers carefully especially on the valves which showed excessive clearance.
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Post by Deleted on Jun 17, 2020 13:20:15 GMT
Water down the exhaust is the frequent cause of valve stems rusting. On the valves that are left partially open this will lead to them not closing under spring pressure when the camshaft is turned. On a stopped engine there are generally 3 valves open.......................... But fortunately on the BMC 1.5D the valves are not inclined with respect to the piston crowns which are flat. So on cranking the rising piston knocks the stuck valves closed, imposing a shock load on the rockers and pushrods. It is rare in my experience to get a bent valve. I have found that usually it is the rocker that gets bent, the pushrods being long and hence slightly flexible, less likely so. I would inspect the rockers carefully especially on the valves which showed excessive clearance. Thanks for that Isambard. I will have a good look.
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Post by Deleted on Jun 17, 2020 13:27:30 GMT
Water down the exhaust is the frequent cause of valve stems rusting. On the valves that are left partially open this will lead to them not closing under spring pressure when the camshaft is turned. On a stopped engine there are generally 3 valves open.......................... But fortunately on the BMC 1.5D the valves are not inclined with respect to the piston crowns which are flat. So on cranking the rising piston knocks the stuck valves closed, imposing a shock load on the rockers and pushrods. It is rare in my experience to get a bent valve. I have found that usually it is the rocker that gets bent, the pushrods being long and hence slightly flexible, less likely so. I would inspect the rockers carefully especially on the valves which showed excessive clearance. Thanks for that Isambard. I will have a good look. I've emailed Ken McCallum and requested you receive a basics mechanical course.
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Post by Deleted on Jun 17, 2020 13:35:46 GMT
Thanks for that Isambard. I will have a good look. I've emailedΒ Ken McCallum and requested you receive a basics mechanical course.Β I did not require it in my current position as it happens. My two year BTEC in marine engineering for which I received a merit award was obviously a bit of a waste of time It was 23 years ago though, half a lifetime and my brain has since gone off somewhat. Berkshire College of Agriculture 1995/96. Always been a theory person never been any good hands on with stuff like this. I could explain in laboriously complex detail the entire functioning of a diesel engine but shit at fixing problems.
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Post by Deleted on Jun 19, 2020 21:26:02 GMT
Push rods seem to be ok as do the rockers.
I am now wondering if when the boat was decommissioned the bloke loosened off the tappet adjusters to leave all valves closed. Deliberately - in order to prevent half open valves from sticking...
It's the kind of thing that could well have happened but I was unaware of it.
I'll check the other engine for a possible similar situation.
Anyone looking at the boat will immediately see that the attention to detail is on a different level to most things you come across so it's not impossible it has all been thought through.
Seems to make sense to me but you would have to know it had been done...
Another thing I had when I bought the boat was leaking fresh water system as the copper compression parts had been disconnected including parts only accessible by removing lining panels which are designed to be removed. Removable panels have cheese head screws whereas fixed panels have countersunk screws...
Frost protection obviously. Boat to be unused for a while needs looking after doesn't it.
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Post by Andyberg on Jun 19, 2020 21:34:23 GMT
Bollox!
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Post by Deleted on Jun 19, 2020 21:42:23 GMT
In medical terms it is known as "hyper-systemising" brain attempts to make sense of everything or arrange everything so that it makes sense. I do it all the time. .. The procedure described will also look after the valve springs and in the (unlikely) event of major water ingress into the exhaust system it significantly reduces the chance of getting water into the bores which is definitely something worth reducing the chances of.
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Post by Deleted on Jun 19, 2020 22:09:01 GMT
The procedure described will also look after the valve springs and in the (unlikely) event of major water ingress into the exhaust system it significantly reduces the chance of getting water into the bores which is definitely something worth reducing the chances of. Pfffft, and you were suggesting I squirt water into my air intake a few weeks back! Ffs! π
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Post by Deleted on Jun 20, 2020 9:08:58 GMT
@bedruthan Yes this was with engine running and hot nothing to do with winterising a disused engine. That's a totally different subject surely you can see that ffs Water in the bores on an engine which is unused for months or maybe years could easily be terminal specially if it then froze. Small amounts of water injected into the air intake of a hot, running engine is not going to cause a problem and -might- be beneficial.
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Post by Deleted on Jul 11, 2020 12:13:17 GMT
Well after some head scratching and checking over all of the valves close properly, push rods same length and not bent, rockers all ok.
What it is is that one of the rockers has been replaced (probably due to bending) and the tappet screw is about 10mm shorter so you run out of thread for the locking nut.
I discovered there were two pushrod lengths so I guess this rocker is for the longer one.
I must look in the drawer and see if by any chance the old rocker is in there with its screw...
Otherwise I need a tappet screw the right length for a BMC 1.5D...
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