Setting Tappet clearances

[F69]

For some time now the annoying sound of "thack thack thack " comes from the top end of my TR6, especially when cold, but not so distinct when hot. Seasoned advice points to the tappets, which I haven't adjusted for 18mths or so, so today off came all the associated gubbins and when I got the feeler guage going I found that some clearances were much tighter than the specified 25mm or 0.010 inches.

Plugs were out so socket on crank nut and away I went. Valves 10 and 12 open adjust 1 and 3 ( or something like that ) and I watched as 10 and 12 opened, but what I couldn't understand was that 12 started to compress well before 10, ( or was it the other way round, cars' downstairs and I'm up here, rats!! ) . I thought they were supposed to move in tandem OR am I right to think that being inlet and exhaust one will open slight before the other.

I know there are many technically minded sixers out there, so can someone give me the definitive on this question.

Many thanks, guys

Edited May 31, 2007 by Richard Goddard

[mikew]

Inlet and exhaust valves on these engines do open at different times, or degrees of revolution, its not like some 4 cylinder engines.

 

To adjust you should use the Rule of 9.

 

To set #1, subtract it from 9 and get 8, therefore #8 must be fully open to set #1 or simply set the tappet which is a mirror image of the closed one.

 

mike

[PJM]

Rule of 13 for a six cylinder, so valve No. 10 & 12 fully open (valves compressed) adjust No. 1 & 3

[jonlar]

Hi Richard, as PJM says above,for 6-cylinder engines, it is Rule of 13 (Rule of 9 for 4-cyls). When no. 12 Fully Depressed, adjust number 1, no. 4 when 9 FD, I'd advise you to only attempt 1 valve at a time (as opposed to 2, if you see what I mean), carefully crank engine around by hand without plugs in. Be aware that if rocker tips have worn and grooved, it is very difficult to set accurately with feeler gauges, there is a "Click-Adjust" (Gunson?) tool, which gives 1/1000" gap per click from its calibrated thread.

Edited May 31, 2007 by jonlar

[Tom Fremont]

am I right to think that being inlet and exhaust one will open slight before the other.

 

This is correct, however the offset is slight enough that the max clearance still exists on both valves to be adjusted.

 

One presumes that the factory had it right when publishing the owner's manuals detailing this method of adjustment . It is possible to adjust them all with ~ 3 turns of the crankshaft this way.

 

For the sceptical, turning the crank another complete turn after the valve's fully open will definitely position the lobe where needed ( upside-down ), but this method will require in excess of (12) turns of the crank

[jonlar]

I thought they were supposed to move in tandem OR am I right to think that being inlet and exhaust one will open slight before the other.

 

Tom is right, this is what is referred to, as "overlap" and depends on the camshaft that's fitted, hotter cams, more overlap. This is done to assist and increase the engines induction - 4-stroke engines, induction - compression - ignition/power stroke and then exhaust stroke, and if you're not totally confused now Richard - I am!

[robgeev]

Main bearing wear.

[F69]

Many thanks for your replies. I shall adjust each one individually, althouth theres' nothing wrong with adjusting 2 valves at a time. Funny thing is that I bought a Click-Adjust from Gunsons, but for the life of me cannot figure out how to set the damn thing up, even with the instructions. ( Better let the wife have a read, I suppose )

[jonlar]

Hi Richard, no, there's nothing wrong at all with doing 2 valves at a time, but I'd make a note of the order and tick them them off, so you know exactly where you are - I had to fit a BN cylinder head to my Pug 405TD April last year, with the one-use H/T head bolts on that, you have to do them up in the correct order to 60 foot lbs or whatever the measurement is (this is to stretch the bolts), then release them in reverse order, then start retorquing to 60 or 80 (can't remember which off the top of my head) then another 220º (which I did with an angular gauge, in increments of 90, 90 and 40) in the correct order - lose your place and have to undo them all and start again!

Edited June 1, 2007 by jonlar

[PJM]

but for the life of me cannot figure out how to set the damn thing up, even with the instructions. ( Better let the wife have a read, I suppose )

 

 

I can send one of my Grandchildren round to decipher them if it helps.........always works with the TV, VCR, DVD etc