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Post by tommydp on Dec 23, 2012 9:35:04 GMT
A follow up on previously discussed timing chain slack..
I just got a new old stock "Moprod" (70s I think) 1800 timing chain (duplex). I put it on a spare block and it has virtually no slack, just like I remember from when I changed one years ago when I was a kid.. The timing marks line up perfectly at TDC for both cylinder 1 and 4 firing and the full lift of cylinder 1 inlet valve is 110 degrees spot on, so should be perfectly timed?
As mentioned before, the chains I have tried recently on the troubled engine have had lots of slack when installed, using the same timing gears and I've had trouble lining up the timing marks..
I'll upload a video later, showing the differences in slack.
Tommy
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Post by kelsham on Dec 24, 2012 9:26:57 GMT
Tommy, reading the post on timing chains made me recall a problem I once had with a Mini.
It refused to run correctly. Eventually I identified the fact that the previous owner had carried out some amateur tuning on it.
Upon deciding to sell it on he removed the special manifold and carb, including the gas flowed head he had fitted and replaced them with the parts he had removed earlier.
Because it was difficult to get at, he left the modified camshaft in place. This was the problem.
What camshaft did you end up with in your troublesome engine?
Regards Kels.
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Post by dave1800 on Dec 24, 2012 13:21:22 GMT
Kels You shouldn't mention the Cxxsxxxt word you will upset Tommy at Christmas! T Because it was difficult to get at, he left the modified camshaft in place. This was the problem. What camshaft did you end up with in your troublesome engine? Regards Kels. |
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Post by tommydp on Jan 2, 2013 23:08:37 GMT
Hi everyone, and a Happy New Year to all of you! Not that cold at the moment, so spent some time with the cars this evening. Here are two videos showing the difference in slack between the NOS, 1970s Moprod chain and a Rolon chain, which I understand is made in India these days. The Rolon chain has been used for a short while in the current engine, but very few miles. I also felt it had too much slack when installing it. The same goes for the one I'm running at the moment, which is of the same brand. Seems far to slack, and when the tensioner takes up the slack it seems to turn the cam, so the dimples get out of alignment. With the Moprod chain, the dimples and crank and cam centres are perfectly aligned all the time. Yes, I know I use different sprockets in the videos, but the results are the same when using the same sprockets. None of the sprockets seem too worn to use. Well, perhaps it's time to get into the timing gears again! I'm quite sure the camshaft can be ruled out... It's a standard cam in good condition, or at least it was last time I checked.. First video shows the old stock Moprod chain, which seems fine to me.  Then the chain I find far too slack..  Regards, Tommy |
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Post by Penguin45 on Jan 3, 2013 1:27:07 GMT
First one looks good, although the top pulley looks like its got some horribly worn teeth on it.
Second one looks really slack...
I take it you took the tensioner off for the filming?
I'd consider doing something about that top pulley wheel.
Chris.
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Post by dave1800 on Jan 3, 2013 5:04:59 GMT
Agree with Chris about the cam pulley - if the teeth are sharp that's also a good indicator of too much wear. The slack on the second chain is unbelievable much much worse than on a chain I had with >200k miles on it - now I see what some MGB owners have been complaining about. David First one looks good, although the top pulley looks like its got some horribly worn teeth on it. Second one looks really slack... I take it you took the tensioner off for the filming? I'd consider doing something about that top pulley wheel. Chris. |
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Post by tommydp on Jan 3, 2013 7:33:24 GMT
Thanks for the replies! Seems to match reports on various MG forums on aftermarket chains. One had very similiar symptoms, such as varying valve clearances, rough idle, noisier than usual valves, unstable timing marks etc etc.. I suppose such a slack chain will have to cause some trouble..
The tensioner is off for the video, in fact I just put the timing gears on a spare engine to show the slack.
I will have to get new sprockets wheels, if I'm going into the timing gears again. But where to find quality items?! I'm not buying a damn thing anymore that's not original or really old stock, or a known quality item!
Hope this is useful to someone! As someone pointed out on an MGB forum: "Restoring and maintaining an MGB these days is like walking through a minefield of bad reproduction parts"
I agree and steer well of those things in the future..
T
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Post by aussietony on Jan 3, 2013 13:19:23 GMT
Hi Guy's,
You should be able to buy Reynolds chain by the meter, I know I can here in Australia it is quality chain and will last as long as the OEM one and it should be inexpensive as you would be buying it from an agricultural supplier.
Tony
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Post by tommydp on Jan 5, 2013 16:41:35 GMT
Oh yes, genuine NOS BMC cam and crank sprockets are on their way:-)
Regarding the chain, I'll use the old stock one shown in the first video. I guess the slack will be even less with new sprocket wheels.
As I'm now about to get the white one ready for the MOT, I'll get into the blue one and the timing chain later. Perhaps a spring/ summer project. I'm thinking of getting a cylinder head rebuilt by Burgess to fit at the same time. And I will get someone to help me checking the cam timing. I hope I will have no more strange issues when installing quality timing gears.
Regards, Tommy
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Post by Penguin45 on Jan 5, 2013 19:49:35 GMT
Come on, tell! Where'd you get them from?
Chris.
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Post by tommydp on Jan 5, 2013 21:00:59 GMT
;D I'll make a quiz, a difficult one..  |
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Post by Penguin45 on Jan 8, 2013 1:14:06 GMT
I was talking to my friend Adrian on Sunday evening over a few beers, and we got round to chains. This was more of a linky conversation, rather than a kinky one! Ady is a classic motor bike racer and goes absurdly fast on a Yamaha RD350. He expects a drive chain to be worn out in 300 miles.........
With regard to our timing chains, he made several very valid points. Worn teeth "snatch" the chain, rather than letting it roll round the teeth as you would expect. Chains have an excellent service life if running under constant tension; snatching causes "bouncing" in a ripple effect along the chain and will wear it out very quickly.
Quick check on a chain is to lay it out flat along a work bench, then hang as much as is practical over the edge and see how far the chain droops. I wouldn't mind betting that the stretched chain shown in the video bends or droops far more than the other one.
We need to understand what a chain actually is. Each link is really two bearings. The pin is the holding device and the centre tube in each link is the running bearing. When new, each one is packed with grease. This disperses with load and faster if the chain isn't running properly. Hence slack and play can appear very quickly if the chain is jolting or snatching.
That said, Ady explained that a new chain (ANY new chain) will stretch slightly almost immediately, BUT, should then settle down for a decent period.
His description of doing 120mph down the straight at Cadwell Park and realising that he could actually hear the drive chain rattling was both funny and rather scary. Had it jumped the sprocket it would have trashed a very fine race engine and probably thrown him clean off the bike.
Chris.
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Post by tommydp on Jan 10, 2013 12:03:40 GMT
Very interesting, Chris! I'll certainly think of this when getting into the timing gears again, which I hope will be the last time for many years..
So, how to make sure the chain is running correctly from the start?
All new cam and crank sprockets are an advantage, I suppose. Then the sprockets will have to be in line. The manuals say you should be able to put a steel ruler across the teeth of the two sprockets to make sure they are in a straight line. Adjustments here are done by the shims behind the crankshaft sprocket.
Then, I guess I'll have to check the camshaft endfloat. As I understand, this is only given by the camshaft locating plate, so trying another plate is the only way to alter the endfloat if it's not within specifications.
Finally, you need a good tensioner that also allows correct lubrication of the chain.
Am I missing something?
I'm really doing this for the last time in a while now, and don't want to ruin my precious BMC parts, which I btw got in Sweden:-)
Regards, Tommy
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