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Post by tommydp on Aug 8, 2011 9:07:08 GMT
Hi Tommy Hope you enjoyed your break. It's been very wet (ie big floods) here so I have returned a day early. Here is a link showing the small changes in cam timing to the MGB when they changed from duplex to single timing chains, see the picture about 1/4 the way down the file showing the keyway changes - it is quite probable that the Crab 1800 followed a similar change. The bottom line is that whether you use the duplex or single arrangement it will make only a marginal difference and not be the cause of your problems. www.1977mgbsupercharger.com/restoration/default.htmlHope you are all fired up again! good luck David Hi, Dave! I've had a nice journey, and my motivation is back:-) Very interesting link, lots of useful information. Well, I'm into the timing gears again. I'm about to check the valve timing as it is now, before going further. I've established tdc by using a tool that fits inside the plug hole, whit a rod in it. Turning the engine forward and backward until piston touches the rod shows that the marks on the pulley and timing wheel are spot on. I've tried to measure the valve timing, setting valve clearance to 0.020 on cylinder one inlet and exhaust valve. As far as I can tell, there's something obviously wrong. I'm absolutely sure this is a good condition standard 230 cam, 5-45-40-10. The figures I get don't match at all, it's not logical. I check the value when the pushrod just can't rotate for opening and just can rotate for closing. I don't have a dial gauge. I get 10-55-40-15.. As far as I can see, the inlet valve is open far too long. It opens 5 degrees earlier and closes 10 degrees off. Exhaust valve opens at correct time, closes 5 degrees off. 10+55+180= 245 40+15+180= 235 It just doesn't make sense. I suppose my readings aren't accurate enough then. Anyway, on the bright side, there seems to be something obviously wrong here. Even though my readings are a bit off, that exhaust valve is open way too long. I'll try to do it more accurately. It's a bit hard to establish the correct point. I'll try to get a proper timing disc today, which might be a bit better than the one I've got. Updates to come:-) Regards, Tommy:-) |
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Post by dave1800 on Aug 8, 2011 11:31:02 GMT
Hi Tommy
Good you enjoyed your break. It's always difficult to be spot on but this look strange. Try checking all the other cylinders to get an average reading and minimise your reading errors. Only turn the crankshaft in one direction (it's normal rotation) so that any slack in the chain stays consistent.
Post again when you have a better timing wheel. When you take the chain and sprockets off try and put them back to get the distributor drive to engage in the correct position. If you can get it close to 5,45 for the inlet, I would be tempted to try this.
regards
David
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Post by tommydp on Aug 8, 2011 22:37:07 GMT
Hi Tommy Good you enjoyed your break. It's always difficult to be spot on but this look strange. Try checking all the other cylinders to get an average reading and minimise your reading errors. Only turn the crankshaft in one direction (it's normal rotation) so that any slack in the chain stays consistent. Post again when you have a better timing wheel. When you take the chain and sprockets off try and put them back to get the distributor drive to engage in the correct position. If you can get it close to 5,45 for the inlet, I would be tempted to try this. regards David Ok, tried with another timing disc now. Done it over and over again on all cylinders. I have been as accurate as I can and the results are the following on all cylinders: 15-45-50-10 I adjusted the timing disc for exact tdc, using the rod tool to touch the piston and finding the middle of the two points when it touched the piston. So I'm quite sure the tdc is very accurately established. I use a steady piece of wire as a reference, the point of it almost touching the timing disc, so very accurate too. Strange the opening of the valves are 10 degrees off, while the closing is correct for both.. I tried other settings of the chain of the sprockets, but have so far not found acceptable readings. Is it normal for the tensioner to be pushed back, once in every crank revolution, when engine is rotated in normal direction? Well, willl have another go tomorrow:-) Regards, Tommy:-) |
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Post by dave1800 on Aug 9, 2011 0:00:36 GMT
Ok, tried with another timing disc now. Done it over and over again on all cylinders. I have been as accurate as I can and the results are the following on all cylinders: 15-45-50-10 Strange the opening of the valves are 10 degrees off, while the closing is correct for both.. Regards, Tommy:-) Hi Tommy Can you do the same check on your Marina and /or another assembled block to see if this is an anomaly of the cam or something to do with your measuring technique, although I am baffled to think what. Anyone else have an answer? The only positive indicator that something is wrong with the cam installation is that the distributor drive shaft is offset. What are the readings if you set it to line up as per the Marina and as "normal". I suspect the tensioner moving in and out as you manually turn the engine isn't a problem and won't happen when the engine is running, but look at your other engines. I have had a quick look at other B and A series cam profiles and cannot see any where the inlet period is greater than the exhaust (apart from one full race cam). Are there any markings on the end of the cam - numbers, bars etc? Not saying your measurements are wrong, I'm just a bit lost! You could also try measuring the peak of the cam by checking the valve opening / pushrod lift. On these engines the cam profile should be symmetrical so for example the inlet valve 5,45 (5+45+180=230) the peak should be at 230/2 = 115 degrees which equates to 115-5 = 110 abdc = 70btdc if my maths are right. Another way of checking is always helpful. Hope this makes some sense regards David |
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Post by tommydp on Aug 9, 2011 9:16:17 GMT
Ok, tried with another timing disc now. Done it over and over again on all cylinders. I have been as accurate as I can and the results are the following on all cylinders: 15-45-50-10 Strange the opening of the valves are 10 degrees off, while the closing is correct for both.. Regards, Tommy:-) Hi Tommy Can you do the same check on your Marina and /or another assembled block to see if this is an anomaly of the cam or something to do with your measuring technique, although I am baffled to think what. Anyone else have an answer? The only positive indicator that something is wrong with the cam installation is that the distributor drive shaft is offset. What are the readings if you set it to line up as per the Marina and as "normal". I suspect the tensioner moving in and out as you manually turn the engine isn't a problem and won't happen when the engine is running, but look at your other engines. I have had a quick look at other B and A series cam profiles and cannot see any where the inlet period is greater than the exhaust (apart from one full race cam). Are there any markings on the end of the cam - numbers, bars etc? Not saying your measurements are wrong, I'm just a bit lost! You could also try measuring the peak of the cam by checking the valve opening / pushrod lift. On these engines the cam profile should be symmetrical so for example the inlet valve 5,45 (5+45+180=230) the peak should be at 230/2 = 115 degrees which equates to 115-5 = 110 abdc = 70btdc if my maths are right. Another way of checking is always helpful. Hope this makes some sense regards David Great, Dave! I'll do some more work later today, checking the peak of the cam too and comparing to other engines. My readings may very well be a bit off, however I can't see how I can do it more accurately now:-) Anyway, found this info on the tightly written MG page. Could it be an issue with the 1800 mk2 head on a Princess block? Well, I'll report back after further work and investigation:-) Regards, Tommy:-) Be aware that the heads used on the 18G through 18GK Series engines and those used on the 18V Series engines are of
different thicknesses due to the different depths of their combustion chambers and redesigned coolant passages of the 18V
Series engines. As a result, the heads used on the 18G through 18GK Series engines are taller (3.172") than those of the 18V
Series engines. As a consequence of this, their pushrod/tappet combinations have different included lengths (277mm 18G
through 18GK, 274mm 18V). As a result, if you should choose to install the later 18V bucket tappets and longer pushrods into an
engine equipped with one of these earlier heads, it will be necessary to screw their rocker arm ball adjusters 3mm further towards
the bottom of their travel. This will result in an increase in the effective length of the fulcrum arm of the rocker, with a
consequential slight decrease of valve lift. |
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Post by dave1800 on Aug 9, 2011 10:00:41 GMT
I would guess you have a Crab block as you have mentioned the scallop shaped cut outs for the larger inlet valves. I have never taken the head off a Pricess 1800 but can't see why it would have the cut outs as it uses the smaller inlet valves like the Mk1 Crab.
Perhaps someone can advise?
No matter what you do with tappets, push rods etc as long as you set the valve clearances right it can't make any difference to the valve timing which all takes place below the head level. I can't follow the argument in the article you have copied about valve lift it doesn't make sense to me but I may well be missing something.
I suggest concentrating on bottoming out the cam timing issue by taking the other measurements. As far as I have been able to determine all B (and A) series engines have the distributor drive at 1-7 when aligned correctly and the fact yours doesn't needs to be investigated further.
regards
David
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Post by tommydp on Aug 10, 2011 7:16:15 GMT
OK, some progress, though I'm still confused about the readings of the cam.. I just can't see anything wrong with my tecnique. After all I was able to identify the 285 camshaft, and the fact it was 10 degrees out using the same method. When timing that cam in the correct position, I was able to establish readings spot on, or within 1 degree off the specs.. So what could I be doing wrong now, I'm not sure:-)
I've not been able to check out the Marina yet, as it's standing outside and it's been raining cats and dogs for days:-)
I started from scratch again, installing the timing chain as per manual, straight line across timing marks and centre of sprockets. The distributor drive was definetely more correct at tdc now, 2-8 o' clock. I had made a mark of its previous position, which was more like 1-7. To begin with, I also marked my desired position of the dizzy drive gear, and it actually matched this now. Also, the timing marks, do match up at tdc, they seemed to be a bit off as it was.
I now removed the rockers from cylinder one, sliding the exhaust rocker off the shaft and pushing the inlet one off the pushrod, so rhe shaft is still in place. I tried this to determine the timing by the pushrod. Sadly, I still don't have a dial gauge, the only place I can get one here is sold out...
Anyway, watching the pushrods closely, it seems to me they match 5-45-40-10..
Then the confusion starts: if I now watch cylinder four, which rockers are still in place and at correct valve clearance for checking, the inlet valve seems to open at 5, however at 45 the valve is still open! The pushrod is not free to rotate until 55! That's 10 degrees off, would you believe that? Amazingly, similiar readings occur for cylinder one when installing the rocker again..
So, for some reason beyond my understanding, the inlet valves are open 10 degrees longer than they should..
I'm sure this is the cause of my trouble, the challenge now is to solve this. I'm not putting it together until I've got spot on readings on all cylinders!
Regards, Tommy!
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Post by dave1800 on Aug 10, 2011 7:34:46 GMT
Tommy, Alexander and others
As a diversion from Tommy's current cam problems which seem to grow more peculiar by the day, you may be surprised to learn (I was) that in the BL Special Tuning document for the MGB, Stage 2 tuning they recommend changing the camshaft with timing 16,56, 51,21 to one with a profile of 0,50,35,15. This is the 1800Mk2 cam profile 5,45,40,10 offset by 5 degrees.
It says this gives 2-3 BHP more in the low to mid range and only loses out marginally after 5,000 rpm.
If this is the case why fit the hotter cam to the 1800S, MGB and Marina TC (I believe) with the potential fuel penalties and loss of low down torque?
Any thoughts
David
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Post by dave1800 on Aug 10, 2011 7:55:11 GMT
I've not been able to check out the Marina yet, as it's standing outside and it's been raining cats and dogs for days:-) Anyway, watching the pushrods closely, it seems to me they match 5-45-40-10.. Then the confusion starts: if I now watch cylinder four, which rockers are still in place and at correct valve clearance for checking, the inlet valve seems to open at 5, however at 45 the valve is still open! The pushrod is not free to rotate until 55! That's 10 degrees off, would you believe that? Amazingly, similiar readings occur for cylinder one when installing the rocker again.. Regards, Tommy! It sounds as though the rocker shaft is flexing while you turn it slowly- but is unlikely to be able to flex so much when the engine is running. There should be a 0.005" shim under each of the two centre rocker shaft pedestals which are supposed to pretension the shaft. I think you need to wait until it stops raining and look at the Marina. But if you get the right reading with the push rod disengaged and the distributor drive in the 2-8 position, then it sounds to me as though this is correct. This is interesting. regards David |
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Post by tommydp on Aug 12, 2011 23:37:06 GMT
Well, I haven't quite given up yet.. Perhaps I should have:-)
The nightmare goes on, it's just not possible to get the cam reading right. Had a look at the Marina and it's spot on, also by using the 0.020 valve clearance method. So I suppose my method is accurate enough.
The timing of the 1800 is out of this world. Trying over and over again, using different sprockets and chains, the average is 10-55-40-15. Totally crazy.. Marks are then opposite eachother, and distributor drive gear still seems too far advanced, ie more 1-7 than 2-8. I've tried to move one tooth in both directions, but then the timing gets way off.. Seems the results are the same when watching the pushrods only, rockers removed.. And yes, I've tried a different cam too, same results..
The cam wich was in it is the correct mk 2 cam, part number is stamped on it. It's as new, just like when I installed it. Followers are unmarked. I now installed a Princess cam in quite good shape. No part number on the Princess cams, there's only a dash of yellow paint on them, whatever that means. The exhaust lobes are somewhat fatter on the Princess cam, not as peaky as the 1800, inlet lobes look the same. Height of the lobes are the same.
Well, whatever, it should be possible to get some reasonable readings on them both I guess. I'm really stranded here, and just can't put it together before I get the readings right. I'm most concerned about the inlets, which seem to stay open far too long. I suppose this is an indication of the mixture trouble I've had, as well as what really looked like flooding of some cylinders after idling for a while.
I can't see what I'm doing wrong. I mean it's not possible to install the cam incorrectly? Crank at tdc, cam key at 2ish, lining up sprockets with a straight line between centre of sprockets and marks and then putting chain on, while centre line still straight through sprockets and marks. Then sliding the timing gears with chain on engine, then activating chain tensioner.
So, what about chain and tensioner? I've tried different chains, some have few miles on them. The chain has a lot of slack before the tensioner is applied, but I suppose that's ok, but I seem to remember there was virtually no slack when I put a new chain on an 1800 years ago. Perhaps the fluctuating timing marks when using the strobe is some indication on a fault here?
Ah, if only a Gold seal unit would come up! I'd buy it at any cost from any part of the world:-)
That's all for now:-) Updates to come..
Regards, Tommy:-)
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Post by dave1800 on Aug 13, 2011 0:44:11 GMT
Tommy Don't panic! I see you posted very late at night so guess you may be over-tired as well as frustrated. I'm sure we've all been there, I have! Let's analyse the position. (a) In your earlier post you noted you had the distributor drive in the 2 o'clock 8 o' clock position and measured the cam at 5-45-40-10 (correct) by following the pushrod when it was disengaged from the rocker. Therefore the camshaft valve timing is correctly set up, the cam profile is correct and the tappets are free. So the problem is elsewhere. (b) The fact that when the pushrod is engaged the inlet valve stays open for another 10 degrees can only be due to the rocker shaft flexing and pushing down on the pushrod even though the valve is actually closed and / or it is badly worn and sticking. To prove this, disconnect pushrods that are putting load on the shaft, and repeat the testing (eg as inlet 1 closes, inlet 3 is opening, so engage pushrod inlet 1, disengage pushrod inlet 3 and see if inlet 1 now closes at 45 degrees without the load from inlet 3. - disengage other pushrods as appropriate). To determine if the rocker is sticking on the shaft, turn the engine until the inlet valve should be closed to say 48 degrees with the pushrod in place and see if you can release it by moving the rocker on the shaft by hand. (c) I suggest you go back to the camshaft that gave you the above correct measurements with the distributor drive in the right position and run the engine. There may be a need to change the rocker shaft, but this can be done later and won't involve you taking out the radiator again! Here is another video (of a MGA OHV engine but very similar) showing wear on the rocker shafts and also just how tolerant these engines are to unbelievable levels of a worn out cam, among other things - as long as the cam timing is right! It may make you feel better. universitymotorsltd.com/videos-display.php?id=144If anyone else has some ideas please comment, it is difficult trying to diagnose from 6,000 miles away! Regards David |
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Post by tommydp on Aug 13, 2011 9:09:23 GMT
Tommy Don't panic! I see you posted very late at night so guess you may be over-tired as well as frustrated. I'm sure we've all been there, I have! Let's analyse the position. (a) In your earlier post you noted you had the distributor drive in the 2 o'clock 8 o' clock position and measured the cam at 5-45-40-10 (correct) by following the pushrod when it was disengaged from the rocker. Therefore the camshaft valve timing is correctly set up, the cam profile is correct and the tappets are free. So the problem is elsewhere. (b) The fact that when the pushrod is engaged the inlet valve stays open for another 10 degrees can only be due to the rocker shaft flexing and pushing down on the pushrod even though the valve is actually closed / or it is badly worn and sticking. To prove this, disconnect pushrods that are putting load on the shaft, and repeat the testing (eg as inlet 1 closes, inlet 3 is opening, so engage pushrod inlet 1, disengage pushrod inlet 3 and see if inlet 1 now closes at 45 degrees without the load from inlet 3. - disengage other pushrods as appropriate) (c) I suggest you go back to the camshaft that gave you the above correct measurements with the distributor drive in the right position and run the engine. There may be a need to change the rocker shaft, but this can be done later and won't involve you taking out the radiator again! Here is another video (of a MGA OHV engine but very similar) showing wear on the rocker shafts and also just how tolerant these engines are to unbelievable levels of a worn out cam, among other things - as long as the cam timing is right! It may make you feel better. universitymotorsltd.com/videos-display.php?id=144If anyone else has some ideas please comment, it is difficult trying to diagnose from 6,000 miles away! Regards David Hi Dave! Thanks a lot! Yes, I'm getting really frustrated:-) I agree the rockers could be an issue, as there seems to be a difference between measuring pushrod vs rocker and watching pushrod alone. I'm having trouble finding exact timing for the pushrods alone, but it seems the inlet closes to late, 55, then too. Yes I managed to get what looked like reasonable readings as well as drive gear setting, watching the pushrod alone, so I'll try to get back to that setting. Can't believe why it's suddenly impossible to get this setting again.. I've switched between different chains and sprockets, so could perhaps be an issue here. I still find the chains to have lots of slack when installed, before the tensioner is activated. Not sure if this is critical. The rocker shaft is new. It's from a MGB supplier, however the part number of the shaft was same as 1800. The rockers have a different number though. I've checked number one inlet when all other pushrods and followers were removed too. Readings remain the same when pushrod just contacts and just releases.. Regards, Tommy:-) |
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Post by dave1800 on Aug 13, 2011 12:29:06 GMT
Just try the permutations in a controlled manner and keep a written record so you don't get confused. It may be a good idea to mark all of the sprockets and chains. I assume you are back with the cam with which you got the right readings a few days ago? Pay special attention to the relationship of the sprocket key ways to the teeth to see if any are different - offset.
If the chain is a bit slack before the tensioner engages try using a shorter one. I would advise sticking to the duplex arrangement.
There can only be a limited number of permutations; hope you get lucky early. I think the critical things to get right are the inlet valve opening at 5 degrees plus or minus 2-3 degrees AND the distributor drive in the 2-8 position.
Good luck
David
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Post by tommydp on Aug 13, 2011 16:32:13 GMT
If the chain is a bit slack before the tensioner engages try using a shorter one. I would advise sticking to the duplex arrangement. The current chain (duplex) has more than 1 cm of slack when installed without the thensioner. Seems a bit to much in my opinion. Unfortunately they all seem to be the same length. Some of them have hardly been used. As far as I can see all sprockets have the marks in the exact same spot in relation to teeth and sprockets' keyways. Goes for both simplex and duplex. Simplex crank sprockets have a triangular arrow like mark instead of a dot, that's the only difference as far as I can see:-) Regards, Tommy:-) |
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Post by Penguin45 on Aug 13, 2011 21:25:18 GMT
I've been following this with some fascination; Dave and Tommy seem to have the patience of saints. Not sure that I can add anything on the purely technical level, but the following observation springs to mind. It's a tuned engine and logically there would only be one issue to cause poor running. As Tommy seems to have a limitless supply of parts (You lucky chap  ), I would suggest stepping back and getting the engine back to "standard" tune as nearly as possible. Standard cam, standard head, etc. From there, change one component at a time and see what happens. If it's fine, swap it back out again and fit the next component until it starts playing up. It's a process of elimination. I suppose it is possible to just push the tuning too far and she just won't have it - apparently this is a common problem for VW "boy racers" - I do hope not. Duplex chain is the same as the "A" series engine and is as cheap as chips, so don't mess about, buy a new one. Fingers crossed for you, Chris. |
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), I would suggest stepping back and getting the engine back to "standard" tune as nearly as possible. Standard cam, standard head, etc. From there, change one component at a time and see what happens. If it's fine, swap it back out again and fit the next component until it starts playing up. It's a process of elimination.