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MG TD TF 1500 - Timing chain at TDC

Hello everyone. I hope the covid-19 has not affected anyone. I am checking the engine because it is not going well and I have removed the timing chain cover. I have discovered that the mechanic who made the restoration did not take into account the rule of 13-15 and is at 14-14, but what I do not understand is if this position that I show in the photo of the crankshaft and the camshaft corresponds to TDC for cylinder 1 (The photo is not of my engine but it is the same approximate position). I appreciate the help they can give me.


Gabriel Martínez

Gabriel, has the engine run poorly from the day you first started it after overhaul?

Regards, Tom
tm peterson

1) Both gears have a mark, usually a "T". Most new chains do not have marked links; if yours does not, mark one link with paint or nail polish, count 13 links and put another mark. You will have 13 links on one side and 15 on the other

2) Turn the crank and cam gears so they slip on the crank and cam keyways with 13 links on the tensioner side and 15 links on the other. See the workshop manual to be clear on this - it is harder to explain than look at the picture. If your engine is on the workbench, be sure to turn the WSM picture in the same direction.

Tom Lange
MGT Repair
t lange

T. Peterson, I'm not done, I just started and I'm asking to do it correctly. T. Lange, I have the WSM and I have seen all the posts in BBS on this subject but nowhere is it said how TDC is positioned according to the position of the crankshaft and the camshaft. I think the car has always run slow so I want to repair what is wrong.
Gabriel Martínez

If you have a Blowers WSM (Page 119) there is an excellent photo of the orientation the shows there the cam and crank shaft keyways face for correct timing. The crank key is in line with plane of the engine block’s pan rail. The cam keyway faces up and just slightly to the left of a line between the center lines of the cam and crankshaft. Newer gears sets have been found to not have correct reference marks or none at all. I don’t rely on them. If in doubt use a dial indicator to check the valve cycles and compare to the cams spec sheet.


W A Chasser

If your gears do not have the T marks (I have not seen one with no marks), follow Bill's guidance above to mark the sprockets.

If they ARE marked, the point is not to insert the chain at TDC, but to time the cam and crank correctly in relation to each other. This happens when you fit the sprockets over the cam and crank noses when the T marks and marked chain are properly aligned and spaced. It does not matter where the pistons are sitting when you assemble things, as long as the marks and chain spacing are lined up correctly.


Tom Lange
MGT Repair
t lange

My concern is that trying to improve the engine will break it. I have taken a photo in the same position of Chasser's message. The marks and position of the crankshaft key can be seen. I have mounted the engine of my MGA after machining it and in that case the WSM does mention the TDC, but this engine I did not do and I think that the WSM does not speak of the TDC because it assumes a correct alignment between crankshaft and cams following the marks and position of the chain, but I have no way of detecting if these marks are correct or I don't know how to do it.


Gabriel Martínez

this photo may help with checking the alignment.it shows the relationship of chain to keyway position.I always photo for my own peace of mind when I do an enine
Download the image and expand it
Ray TF 2884

Ray Lee

Have you marked the chain with 13 and 15 links? Even though you have not dropped the sump, you can check if all is aligned. Align the chain mark with the marked cam sprocket, then carefully turn the crankshaft with the crank until you can see the marked crankshaft gear and chain mark. They ought to align.

Your sprockets will either have marks or not; although I have never seen a sprocket without marks, I have never even HEARD of a sprocket that had incorrectly-positioned markings.

Trust what you in front of you.

Tom Lange
MGT Repair
t lange

Tom, I have purchased timing gears with errant markings or no markings which is why I stated it. I have a sprocket that was marked erroneously on the backside which didn’t correlate with the front face when flipped. Rely on the key way positions first and counting links second as a back up measure. If there is any doubt use a dial indicator. It is very easy to get cam timing wrong. I built more than a few of these and even I’ve made mistakes setting up cam timing. I now take the time to verify with a gauge. I don’t enjoy R&Rs to correct camming errors.
W A Chasser

Bill - Cam and crank sprockets are a critical engine part. If they are wrong they are wrong, and only by knowing the source can we avoid them. Please let the forums know.

Tom Lange
MGT Repair
t lange

I can’t tell you the manufacturer or where it was originally sourced. I purchased it from a vendor at a British field meet several years ago. I ended up using it by studying the Blowers pic I posted.
W A Chasser

To answer your original question Gabriel
If the crankshaft is set to 1-4 on tdc then the markings should be like in the pic. you originally posted and also the one Ray posted -BUT it doesn't 'have' to be exactly on tdc to do it , just close

The pic. Bill posted from the Blowers WSM (Page 119) is also correct but misleading as the crank has been turned 90deg clockwise----The timing marks still line up but it's better practice to do it at TDC

With your chain at 14-14 the camshaft timing would have been advanced 17 crank deg, -it'll still go but very sluggish and won't rev out properly, you should have a noticeable improvement with it set up correctly

Any pics of how yours was set up when you pulled the cover off-------

willy
William Revit

I think I am understanding some things with your help. I remember starting the engine after restoration with terrible bangs (from this 10 years ago) and having to delay the distributor as much as possible to avoid them. The marks in the chain are a guide but they are not very necessary, I think that if I do them I will get the configuration pattern repeated every twenty times as the manual says and not every two times as I see it now without taking into account the chain link but the distance between the marks counting links. I'm going to check it. The photo I have put is just as I found it and you can see the marks on the sprockets. The mark that can be seen on the crankshaft is correct, it is opposite to the key. I don't know the camshaft mark, you can't see the position of its key. I will disassemble and observe.
Gabriel Martínez

Taking as reference the photo at the beginning of the topic, in this position my engine is in TDC with rotor pointing at 4. This is repeated every two turns of the crankshaft and marking the links with white paint, they coincide every 8 turns. If someone sees something strange, tell me.
Gabriel Martínez

Gabriel,
If you can remove the camshaft bolt and oil thrower. Turn the crank to TDC and photograph straight on. This will show us if both the keyways are in the same position ie at 12 oclock. Only at TDC will they both be at this position, it is quite obvious when they are not.
Ray TF 2884
Ray Lee

I have installed a chain with the white links in the wrong place(this was in the late 80s). I luckily caught it when installing and timing the dizzy. So yes, count links (or pins x 2) and better yet use a degree wheel. George
George Butz III

Gabriel
Firstly, sorry I missed seeing your later pic. of your own engine
I agree that going by the dots the cam. timing is not lined up properly, it looks to me to be 1 tooth (half a link) out--
You are correct in saying the timing re-aligns every two turns as this is how a 4stroke (induction compression power exhaust) engine works
BUT it is impossible for your chain markings to line up every 8 turns
The crank sprocket has 21 teeth the cam 42 --2:1ratio the chain has 60 pins
Mathematically 8 turns of the crank would be 168 teeth which won't devide by the 60 pins

The first time it can all line up is after 20 turns of the crank --420 teeth--7full rotations of the chain

I notice also that you have a non-standard (maybe Moss)camshaft sprocket, -fully machined steel where the std one isn't machined like that and also has a timing dot instead of an inverted T--- same on your crank sprocket
The only real way to find out if the timing mark on the cam sprocket is correct is going to be running a straight edge through the centre line of the camshaft and key and see where it lines up near your dot and get someone on here with a std. sprocket to do the same on a spare sprocket to compare--unfortunately I don't have one otherwise I'd put a pic. of it on here. I suspect that it will be correct but that chain needs refitting correctly for it to work properly
Does the car have a std. camshaft, and what are you setting the valve clearances to--------
William Revit

I would swear that I have counted eight laps but if it is not relevant I do not care. According to the photo everything is correct in the marks. Valves are properly regulated. What I notice is a lack of power at high revs. I am removing the sump and cannot find information on what to do with these inner oil filter nuts, do they loosen or pull the sump as is?




Gabriel Martínez

I enlarged the photo, I agree with William, it is one tooth out. This will give you the symptoms you describe.
Ray
Ray Lee

Gabriel,

I have pulled out from my old parts box the timing chain and sprockets. I have assembled them on the bench, showing the correct alignment. In the attached picture you can see that there are two vertical "PARALLEL" pencil lines on the background sheet.
These are used as a reference.

The right hand line goes through four points, (from top down):

1/ The upper white link.
2/ The "T" mark on the camshaft sprocket.
3/ The key slot.
4/ The sprocket centre.

The left hand line also goes through four points, (from down up):

1/ The lower white link.
2/ The "T" mark on the crankshaft sprocket.
3/ The crankshaft sprocket centre.
4/ The key slot.

The photo also shows the position of the 13 and 15 links of the chain.

This is all the information you need to align the assembly on your engine.

In one of your photos above, I noticed that your chain looks very slack, it seems to have stretched and should really be replaced.

John




J Scragg

Perfect John
Now Gabriel might realise he's a tooth out
I'm a bit worried that Gabriel has been thrown off course by that extra centrepunch mark that someone has punched into the crank sprocket one tooth around from the keyway--why do people do that

With his timing the one tooth out that I suspect it is, camshaft timing would be advanced approx 17 crankshaft degrees which would absolutely kill power in the top end (if it gets that far)and wouldn't do much for low revs power either
William Revit

Gabriel,

For the sake of completeness I will add the following to my previous comments.

If your sprockets have the markings in a different position relative to the key slot, the above method will not work. Ignore them and re-mark the sprockets to be as shown in the photo.
The camshaft sprocket has the mark at 0° from the key slot.
The crankshaft sprocket has the mark 180° from the key slot.

John
J Scragg

It is already mounted correctly. Everything according to your recommendations. William you were right, it's exactly 20 laps to go back to the original position. I cannot buy another chain but I will change it in the near future.
Gabriel Martínez

Gabriel,
If you compare the John and your photo (24 april) you will see that the second tooth anti clockwise from the crank keyway enters the chain at an outer plate, Johns enters at an inner plate, You are one tooth out which will certainly kill your power.
I printed off both photos and I am sure, also my photo of the 23 april shows the same as Johns.
It is amazing how much time you have in lockdown to amuse yourself.
Ray
Ray Lee

sorry double check and I am wrong
Ray TF 2884
Ray Lee

forget the last post, the false pop mark confused me.
IT IS one tooth out.
Ray
Ray Lee

Errors of this nature reliably occur if the block is upside down when the chain is fitted.
G Evans

All good then Gabriel

So you've got the chain on at 13/15 now-?
If you want us to double check for you, if you do another pic with the crank at 90deg round like the one on --23 April 2020 at 21:13:18 BST
we can check for you if you want--or not
cheers
William Revit

Thank you very much William, fortunately my question was about the position of the crankshaft and the camshaft in TDC, but not for not knowing how to count the links of the chains. If you remember, I started the thread saying that I had found 14-14. Thanks to all for the help, everything is already assembled and I cannot take more photos.
Gabriel Martínez

Gabriel,
Sorry I should have read your first post more carefully and realised you already knew that your timing was wrong.
Now it is corrected you will be able to enjoy your TD again (depending on Spain's lockdown arrangements)
Ray TF 2884
Ray Lee

This thread was discussed between 23/04/2020 and 29/04/2020

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