Recognising inlet valves

[Nickol]

Within the Forum it is suggested that the exhaust valves when doing the rocker adjustment are set to 0,015" when using unleaded fuel. I assume that the inlet valves are set to the Standard (cold) Setting of 0,012 " as before.

But how do you recognise which is the inlet and which the exhaust valve? Presumably 1,3,5 etc are inlet,,,,or is it 2, 4, 6 etc ??

[les]

From the thermostat housing number 1-4-5-8 are exhausts 2-3-6-7 are inlets

[oliver90owner]

You can simply look at where the exhaust and inlet manifolds attach to be certain, as they will not cross each other! Another method is to turn the engine in its normal direction and note which valve does what within the 4 cycles.

Works for any engine and can also be a means of determining firing order, if not known.

Other post is right for this engine (like most others of similar design).

Edited to add that the historical convention of numbering, for these engines, is that number one is at the timing end of the engine - whether pistons, valves or spark plugs.

[philthehill]

The 'A' Series always ran better with 0.015" valve clearance even when using leaded fuel but could be noisy.
The 'B' series engine ran with 0.015" valve clearance without any problems.
The 0.015" valve clearance is recommended when using unleaded fuel as the valves run hotter which results in the valves expanding lengthwise so reducing the working clearance.

[Nickol]

From what you say Phil, I should be Setting both inlet and outlet to the larger 0,015", not just outlet. Is that what you mean?

[philthehill]

I always found that the 'A' Series ran better with 0.015" valve clearances for both inlet and exhaust. The only down side is that the valve operating noise can be louder.
The 'B' Series engine was better at absorbing the valve operating noise as the volume of the head for both metal and coolant was larger.
Valve clearance is also dependent on the cam profile. The cam fitted to my Minor requires 0.019" valve clearances.

[Bela]

The 'A' Series always ran better with 0.015" valve clearance even when using leaded fuel but could be noisy.
The 'B' series engine ran with 0.015" valve clearance without any problems.
The 0.015" valve clearance is recommended when using unleaded fuel as the valves run hotter which results in the valves expanding lengthwise so reducing the working clearance.

It was time to adjust the rockers. The WSM says it must be set to 0,012". I found more clearance on all rockers except one. The engine is 1098ccm.

Will 0,015" the better choice?

[Bela]

The 'A' Series always ran better with 0.015" valve clearance even when using leaded fuel but could be noisy.
The 'B' series engine ran with 0.015" valve clearance without any problems.
The 0.015" valve clearance is recommended when using unleaded fuel as the valves run hotter which results in the valves expanding lengthwise so reducing the working clearance.

It is time to adjust the rockers. The WSM says it must be set to 0,012". I found more clearance on all rockers except one. The engine is 1098ccm.

Will 0,015"be the better choice? If so - only for exhaust?

[philthehill]

The workshop manual was written before unleaded fuel became the norm so unleaded fuel would not have been a consideration.

The clearance you found was that determined with feeler gauges or by other means?

It has to be remembered that the top of the valve wears into the pad of the rocker arm and that makes the actual clearance more than can be determined by using feeler gauges.

0.015" is perfectly ok for the 'A' Series engine. It is only 0.003" more in real terms and I suspect that the majority of 'A' Series engines have at least 0.003" wear pockets on the rocker arm pad.

You can get a valve clearance tool that actually measured the real clearance and takes into account the wear pocket.

https://www.ebay.co.uk/itm/Click-Adjust ... 98920eff97

[IslipMinor]

Like Phil, the cam (Calver RC13-OT) I have recently fitted needs 0.016" clearance for standard rockers, so 0.019" for 1.5:1 ratio rockers. The previous cam was a Piper 270 that had 0.012" for standard rockers, and 0.016" for 1.5. In addition I set exhausts to 0.019", so was expecting a real racket from the valve gear, with 0.019" for inlet and 0.022" for exhaust, but was very pleasantly surprised how quiet they are.

[Banned User]

When you take into account the fact that five people will measure 15thou to be five different amounts, 15thou will probably be fine for most cams/engines/etc/etc and how many 15thou feeler gauges are actually 15thou? Even someone with a mic to measure them will probably get a slightly different result to the next person, even if they use the same mic and feeler gauge.

Ergo, don’t get hung up on it imo.

[philthehill]

Poolguy
You are right about the human ability to measure the same valve clearance gap time and time again and get the same result - only using a mechanical means can the same measurement be determined time after time.

On a standard engine the 0.012" plus any wear pit could be classed as satisfactory and acceptable but as regards my own engine the 0.019" valve clearance was determined after extensive dyno testing and so if not set to 0.019" would result in a lower power output on the dyno.

I use a full roller 1.5 rocker assy to maximise valve opening and power output. Having the roller tip to the rocker arm ensures that there is no sideloading/drag on the valve stem and so no wear to the rocker pad.

Even before unleaded fuel I used to run 0.015" valve clearances on my modified 998cc 'A' Series and the engine pick up was much improved.

Rocker clearances are horses for courses but 0.015" including wear pit for a standard 'A' Series is my preference.

Phil

[Banned User]

IMO it’s more important to get the valves all timed the same by varying the clearances than it is to get the clearances all the same, if you’re after optimum power. I assume from what you’ve said that you don’t measure the starting point of the valve opening for each individual cylinder?

[Bowie69]

If you want to be accurate, why not measure them with a DTI ;)

[geoberni]

If you want to be accurate, why not measure them with a DTI ;)

And use it how?
Measure the rise and fall of the actual rocker compared to being both surfaces touching?
I suppose it might work, but probably a faff.

[philthehill]

The starting point of opening and the finish point of closing is set by the profile of the camshaft lobe - nothing else.

I only use Kent Cams billet camshaft not re-ground so they are always spot on but I do have variable vernier timing gears so that the timing can be set absolutely accurately. With the 'A' Series you cannot time each individual cam lobe. If the valve train is set correctly and not worn there is little point in trying to set each individual valve by adjusting the valve rocker gaps.

When setting the start point I do use two DTI gauges - one on the piston and one on the top of the push rod plus the timing disc on the crankshaft to measure the lift at any particular angle of the crank.

Timing the cam 1.jpg (370.07 KiB) Viewed 3130 times

[Bowie69]

If you want to be accurate, why not measure them with a DTI ;)

And use it how?
Measure the rise and fall of the actual rocker compared to being both surfaces touching?
I suppose it might work, but probably a faff.

Precisely, not much of a faff with a magnetic base, just rotate so follower on base of the cam lobe and rock the rocker up and down with the pointer on top of it.

[Banned User]

Phil, the cams may be spot on but the rockers, pushrods and even the followers can vary slightly.

I do have to admit to being slightly over fussy with engine stuff, but that comes from my racing days, most of it isn’t relevant to road engines, but old habits die hard.

[newagetraveller]

This is the tappet adjusting tool.
https://www.amazon.co.uk/Gunson-G4094-C ... B002WT4S1Y

[King Kenny]

I have used one of those tools made by SPQR for thirty years. 8 clicks and the job is done.