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KC Saayman
Frequent User
Username: kc_saayman

Post Number: 94
Registered: 10-2004
Posted on Tuesday, 18 August, 2009 - 02:50 am:   Edit PostDelete PostView Post/Check IP

Hello!

I am busy refurbishing my newly acquired Bentley S1 B527EK, and while I have the tappet cover off for painting, Id like to have a go at setting the tappet clearances. I have previously managed to do this successfully on my six-cylinder 1970 Land Rover, but that workshop manual is a lot more descriptive than the S1 workshop manual, which tells you to do it, not HOW to do it.

Please assist me with the following questions (I have already tried doing a search, but did not find the answers);

1. In what sequence must the adjustments be made? Firing order perhaps? On the Land Rover you have to for example open valve no.1 fully, and then adjust tappet no.6, then open 2, and adjust tappet no.5 etc. Does something like this apply to the Bentley engine?

2. At what point must the adjustment be made? I was told top-dead-centre. What exactly does this mean? Is it when the valve is fully open, or fully closed?

When I did my search I did stumble upon some very valuable information about the tappet heads wearing which then makes accurate adjustment impossible. I will watch out for this.

Kind regards

KC
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Richard Treacy
Grand Master
Username: richard_treacy

Post Number: 1883
Registered: 4-2003
Posted on Tuesday, 18 August, 2009 - 06:36 am:   Edit PostDelete PostView Post/Check IP

Adjust the tappets statically.

Inlet tappet clearance cold: 0.006"
Exhaust tappet clearance cold: 0.012"

If your tappets are noisy, you may go down to 0.004"/0.0010" respectively as a bare minimum.

Like with almost every straight 6-cylinder engine, the sequence is not critical, but easiest to remember is if you do 1-2-3-4-5-6.

Turn the crankshaft as follows:

Open valve No. 6 fully, and set No. 1
Open valve No. 5 fully, and set No. 2
Open valve No. 4 fully, and set No. 3
Open valve No. 3 fully, and set No. 4
Open valve No. 2 fully, and set No. 5
Open valve No. 1 fully, and set No. 6

This applies to inlet and exhaust tappets alike. That way, the tappet is exactly on the back of the cam.

Finally, turn the motor over a few times to rotate the tappets and then recheck in case there is unlikely uneven tappet face wear. If there is any variation on a worn motor, set the minimum to 0.004"/0.0010" respectively.

As the back of the cam is almost impossible to suffer wear, this method is as accurate as you will find. Of course, if the tappets are badly scuffed, unevenly worn or pitted, they may be noisy, but tightening the clearance excessively may quieten them at the expense of burned valves.

RT.
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KC Saayman
Frequent User
Username: kc_saayman

Post Number: 95
Registered: 10-2004
Posted on Tuesday, 18 August, 2009 - 01:34 pm:   Edit PostDelete PostView Post/Check IP

Thank you very much Richard, I appreciate your detailed response.

Just to clarify, valve six is at the rear of the engine, and valve one at the front, or is it the other way round?

Regards

KC
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Richard Treacy
Grand Master
Username: richard_treacy

Post Number: 1884
Registered: 4-2003
Posted on Tuesday, 18 August, 2009 - 01:47 pm:   Edit PostDelete PostView Post/Check IP

6 is closest to your heart as a driver. 1 is at the pointy end nearest the mascot. Just as you stated.
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KC Saayman
Frequent User
Username: kc_saayman

Post Number: 96
Registered: 10-2004
Posted on Tuesday, 18 August, 2009 - 02:29 pm:   Edit PostDelete PostView Post/Check IP

Thank you very much Richard. Much appreciated. I look forward to the weekend so that I can put this into practice!

Regards

KC
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Richard Treacy
Grand Master
Username: richard_treacy

Post Number: 1885
Registered: 4-2003
Posted on Tuesday, 18 August, 2009 - 03:15 pm:   Edit PostDelete PostView Post/Check IP

No problem, and of course remove the spark plugs. That way, and only then, it is safe to turn the crankshaft by turning the fan gently without bending it, clockwise looking from the radiator end.

RHT.

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