Adjusting Valve Clearances: Do I Need To Do It Again?

[Stanpartmanpartwolf]

Everyone- try and find some knowledge elsewhere, perhaps?

What a fatuous thread this has become, so typical of the half-baked confusion between fact & opinion that dominates the web nowadays.

TR engines: no inclined valves, single cam OHV pushrod, "equal" about the centreline. Just obey the ancient rules!

And don't check lash on a running engine. That's just an old joke designed, as Mick implies, to spatter shirts & spectacles alike.

Anyone got an old SPQR tappet adjuster?

[Guest ntc]

I agree Jon,you worked on a inclined valve crossflow Kent lump?

[Stanpartmanpartwolf]

Neil-

no, thank goodness; I've never had the slightest interest in Dagenham Dustbins....

But...I suppose there are still chaps looking for firing order info here.

The real point is: if you're unsure about stuff this fundamental- don't attempt to do the job based on well-meaning guesswork. Find an alternative.

None intended-

XSPMPW

[Motorsport Mickey]

SPQR -Yeah, it languishes in the bottom of my toolbox, never had success with it, probably me.

On the other hand I've used the 9 rule with complete success and saved hours of my life trying to justify a PBI (partly baked idea)of setting the tappets because I'd ballsed setting them up, lol.

Mick Richards

[peejay4A]

Notwithstanding SPMPW's request to end this fatuous thread I'd like a blow by blow description of using a dial gauge to set valve clearances please if someone would be so kind.

[ians]

Rule of 9 rules OK,

 

Remove plugs first to make it much easier.

[AlanT]

These gauges have a spung plunger whose every tiny movement is visible on a dial.

Its easy to see 0.5 thou movement.

 

If you put one on a valve you can watch and record its exact motion as you rotate the cam through one rev.

You will see the exact point of maximum opening.

 

You then put it on the rocker you wish to set and "rock it". You will then see the exact gap between the end of the valve and the rocker tip.

[peejay4A]

Is that all? I'd expected it to be much more esoteric than that. Surely when it's rocking you're on a wide part of the base circle of the one you're going to adjust so does it really make any difference over observing the open valve by sight for the point of rocking? I think I'll experiment.

 

I can see the point of using it to check the measurement on the one you're adjusting but having not tried it I wonder how easy it is to find a point on the rocker exactly above the valve stem that will allow the dial indicator point to rest securely.

Edited October 14, 2013 by peejay4A

[bigmalcy]

Sorry to add one more post to this 'fatuous' thread, and rest assured that I do so only in the interest of sharing my observations:

 

Having 'done' the clearances at TDC on the compression stroke for each cylinder 2 weeks ago, this past weekend I went through the rule of 9 and found that I didn't have to adjust a single clearance.

 

Not sure what that proves (if anything), but either way, I'm as sure as I can be (touching fingers and crossing wood and all that) that the clearances are as they should be.

[TR Mitch]

I understand the point of getting the cam positioned correctly before adjusting but given that you're adjusting when the valve is closed (ie on the heel of the cam), the majority of standard cams have (what looks like) plenty of "null". I've only ever done it by eye & rocking the opposite (9, 13 whatever) valve so it appears fully open. Looking at the shape of the cam heel, I reckon the valve you're adjusting has the same clearance for a good number of degrees of rotation but I would be interested to see what variation you guys get around the heel side rotation.

 

I decided to buy myself a dial gauge and put this to the test as I particularly like Alan's suggestion of using the dial gauge to actually measure the actual gap given the surfaces are not likely to be flat and therefore less suitable for a feeler gauge.

Edited October 14, 2013 by TR Mitch

[RogerH]

This thread has grown a great deal but not actually progressed far.

 

The idea of a DTI to set them spot on tickles my engineering bits and pieces - I like DTI's.

However it could be fun getting the plunger to sit on the rocker arm - not a lot of flat areas - but could still be done.

Also the rocker arm runs in an arc - you will lose an N^th of a thou to this.

 

Apart from very special racing engines do our TRiumph lumps warrant this accuracy.

I did a silly thing a while ago. I didn't misread my feeler gauge I picked the wrong one up. The feeler that said '10' wasn't 10 thou (0.010") but 0.1mm (0.004")

The engine ran faultlessly for a couple of years with no ill effects - and sounded sooooo smooth.

 

SPQR - isn't that a Roman football team.

 

The mark one eyeball is very accurate in perceiving movement (that's why we are all still alive). There is a fair bit of room on the heal of the lobe.

 

The biggest area for error is tightening the locknut on the rocker arm - this can often make the adjuster screw move a little.

The feeler gauge can go from sloppy, tightish to jammed with very little adjustment - how tight is tightish.

 

Do them the way you are happy with. If it works, smile. You will soon find out if it's wrong.

 

Is a committee runnning this thread

 

Roger

[AlanT]

There are actually two types of clock. The plunger type and the Verdict type:

 

http://www.ebay.co.uk/itm/VERDICT-DIAL-GAUGE-/171149125474?pt=LH_DefaultDomain_3&hash=item27d9486762

 

This will work just fine on the end of a rocker. They have only a small range compared to the plunger type, the business end just wiggles a bit rather than sliding up and down

 

The point about having loads of heel is probably right. After you have clocked it you will know this for SURE!

 

You can plot the cam profile, on every lobe if you feel like it, in an hour or so.

 

Years back you would have been into a few hundred quid to set up with these. Imagine me paying £4 for a micrometer in 1966!

But now there is a glut of second hand stuff from closed precision engineering shops as well as all the far-east imports.

 

Since the 1966 mike has no battery it is still as useful now as then.

 

 

 

 

[Stanpartmanpartwolf]

If you think you have a VC issue caused by rocker wear, then...at least you know where the issue stems from. So, if "precision" is the watchword, why the heck prat about buying DTIs and so on; reface/rebush your rockers, fit a nice new tuftrided shaft & use feelers as nature intended.

DTIs are fine for setting up camshafts anew, but surprisingly poor for accurate VC adjustment.

Rule of 9 -QED

[Andy Moltu]

If you want to use a dial gauge to measure valve clearances you have to make sure the gauge is aligned on the tip of the rocker over the mid point of the valve when the valve is closed (back to your rule of 9) and gently move the rocker to take up the slack one way then the other (gentle finger pressure pressing the tip onto the valve and then gentle finger pressure on the push rod end - the difference between the two measurements is your valve clearance.

Much easier to use feeler gauges for this job. If the tips of your rockers are so worn that you feel the feeler gauges are not taking a correct measurement then you are better off refurbing your rocker gear if you want to gain performance.

 

Dial gauges have their uses but this isn't really one of them.

Their role in relation to valves is more for identifying tdc and point of maximum valve lift when timing a camshaft.

[peejay4A]

I tried a little experiment today. On one valve I set the gap using rule of 9. I then used the Macy's technique on the same valve and the gap measured at least 1 thou larger. Empirical but there it is.

[john.r.davies]

To be brutally honest, peejay, if you can really adjust to +/- 1 thou, you're a better man than I am.

Tightening the locking nut almost always introduces a slight turn of the adjusting screw.

Macy's method is not different from Rule of 9/13

 

John

[peejay4A]

I didn't change the adjustment between methods John. I felt significant difference in drag on the feeler gauge and was able to use a fatter gauge using the Macy technique after setting it first using rule of nine.

[john.r.davies]

I don't doubt you, peejay!

 

But the base circle of the cam occupies more than 180 degrees. Almost anywhere on the back will be on the base circle, and Rule of 9/13 ensures that the valve to be adjusted is somewhere within that angle.

 

I suspect that in my own hands, it is difficult to ensure that the adjuster screw doesn't move at all when the lock nut is tightened, which could make that much difference. I'd not be surpised if I went back and found that much difeference, not because the cam was in the wrong place - very difficult with Ro9/13! - but because of observer error.

 

Macy says, "When the intake valve starts to close, adjust the exhaust valve for that cylinder. There’s no way that the exhaust valve is still open toward the end of the intake stroke" and vice versa for the inlet. But get it vice versa wrongly, and there can be a big error - much bigger than the 1 thou you found.

 

John