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MG TD TF 1500 - Vavke Timing

The Manual says that for engines No 24116 onwards the valve timing should be:-

inlet opens 5deg btdc
inlet closes 45deg atdc

ex opens 45deg bbdc
ex closes 5deg atdc

My cylinder head is off and I can attach the plunger of my DTI directly to the tappets. Does "valve opens" mean as soon as I see the DTI registering a lift of the tappet i.e when the valve starts to open or when I see the lift at its maximum i.e. the point at which the valve is fully open. Similarly does "valve closes" mean the point when it starts to close or the point when it eventually snaps shut.

I am presently measuring mine and the critical points appear to be so far out I must be doing something wrong.

Cheers


Jan T

J Targosz

I would say 'inlet starts to open' etc..

I think you have to take in account that normally you would have valve clearance to overcome, but I don't know how many degrees that would take.
Willem van der Veer

Starts to open
W. A. Chasser

I agree with "starts to open"

However, the manual settings ONLY apply if you have the stock camshaft. Any change to a camshaft grind will alter the valve timing specs. So go by the specs of your current camshaft, not by what was written by a camshaft that might have been in the engine 50 plus years ago.
Lew3

So can I work through this logically. I set my pulley protractor to zero at TDC firing stroke for cylinder #1 i.e both valves closed and zero my DTI on #1 exhaust tappet. I turn the engine over as though #1 has just fired. At 45deg before BDC i.e 135dg ATDC the DTI should show the exhaust tappet rising. This will continue rising, reach a peak and then start to fall. At his point the protractor will show 5deg ATDC. OR SHOULD I CONTINUE TURNING UNTIL THE DTI HAS BOTTOMED i.e. THE EXHAUST VALVE HAS SHUT AND THE PROTRACTOR SHOW 5deg ATDC.
Similarly should I see the inlet tappet just starting to rise at 5deg BTDC or should it be fully open at that stage. Should it start to open at 45deg ATDC or should this be the fully open point.

I have made up a pulley protractor with two lines crossing at 90degs. I have marked one side of one of the straight lines as TDC and the other side (180deg) as BDC. If this line is horizontal and matches a mark on the engine when #1 is at TDC firing, with TDC being at 9 o'clock and BDC being at 3 o'clock, 45deg BTDC would be at 10.30, 5deg BTDC just after 8 o'clock, 45deg BBDC at 4.30 and 5deg BBDC at about 2 o'clock.

Now come on guys this a better brain teaser than any suduco and at lot more useful- comments please.


Cheers

Jan T



J Targosz

The angles relate to 'starts to open' and 'finally closes'. You need to set the valve clearances to zero to check the open/close angles - probably easier to use a thin sheet of paper as a feeler gauge.
Perhaps a TC or an AEG122 cam has been fitted.
R A WILSON

.021" is the checking clearance for cam timing for both cams.
From Dave Braun
Len Fanelli

All you need to set is the "starting to open" on #1 cylinder. All other settings are fixed by the cam grind and cannot be changed.
Lew3

This thread was discussed between 28/08/2016 and 29/08/2016

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