1 out of 4 Spark Plugs Looks Odd. Ideas?

[Bill_qaz]

The tappet screw is listed as 9/32 26 uns, so 26 threads per inch.
1 full revolution would be 0.038 so 1/3 turn would give you your 12thou clearance ( 0.0126 )
So you could bottom the screw, so zero lash, you should be able to turn the pushrod but no clearance, now count how many clicks on your new tool is 1/3 of a turn back out and use that as your setting, ruling out the feeler gauge.

[philthehill]

If the threads in the rocker need to be cleared a 1/4" x 26 TPI BSCY cycle thread tap can be used. It does not remove metal as the thread profile is the same but it does remove the crud.

[StillGotMy1stCar]

The tappet screw is listed as 9/32 26 uns, so 26 threads per inch.
1 full revolution would be 0.038 so 1/3 turn would give you your 12thou clearance ( 0.0126 )
So you could bottom the screw, so zero lash, you should be able to turn the pushrod but no clearance, now count how many clicks on your new tool is 1/3 of a turn back out and use that as your setting, ruling out the feeler gauge.

Correct me if I’m wrong, but I think Bill’s calculation only works with an equal Rocker ratio.
I made some notes a while ago, if your adjuster tool has 30 clicks per revolution as the original design, 1 click equals approximately 1.5 Thou, so 8 clicks equals 12 Thou and 10 clicks equals 15 Thou.
I say approximately because I can’t remember if it is dead on or very very close.

Regards John.

[Bill_qaz]

The tappet screw is listed as 9/32 26 uns, so 26 threads per inch.
1 full revolution would be 0.038 so 1/3 turn would give you your 12thou clearance ( 0.0126 )
So you could bottom the screw, so zero lash, you should be able to turn the pushrod but no clearance, now count how many clicks on your new tool is 1/3 of a turn back out and use that as your setting, ruling out the feeler gauge.

Correct me if I’m wrong, but I think Bill’s calculation only works with an equal Rocker ratio.
I made some notes a while ago, if your adjuster tool has 30 clicks per revolution as the original design, 1 click equals approximately 1.5 Thou, so 8 clicks equals 12 Thou and 10 clicks equals 15 Thou.
I say approximately because I can’t remember if it is dead on or very very close.

Regards John.

Is your number of clicks based from a minor engine? If 30 clicks is one revolution of the tool, the tpi of the screw and rocker ratio would determine the clearance. On the screw of this pitch one revolution would be 0.0384. So one click would be 0.0012
You have a point if rocker ratio is unequal it would change the actual valve stem to rocker clearance per click.Do you know the rocker ratio?

[StillGotMy1stCar]

That’s my point, the rocker ratio is 1.25 to 1.

[panky]

The SPQR tools usually comes with a chart showing the number of clicks for different engines.

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[Bill_qaz]

Yes so that makes sense 1 click equals 0.0012 thread x 1.25 rocker ratio = 0.0015 × 8 clicks on your spq chart 8 x 0.0015 = 0.012".
If Stephen tool is 30 clicks per revolution as per yours then the 8 clicks would work.Or if you know the clicks per revolution it can be worked out.
In his post it suggested to set one with feeler to set number of clicks required by the tool but if his rocker arm faces are worn it no more accurate that the feeler gauge. I was trying to give him a method to eliminate the feeler guage.
( see instruction he posted with Gunson tool )
Thanks for the rocker ratio info.

[svenedin]

Thank you for the posts about the Clickadjust tool.

Yes 30 clicks = 1 revolution of the tool, the same as the earlier SPQR tool.

I did wonder how the tool could be more accurate for worn rocker arm faces if it is first set up with feeler gauges on the worn parts. However, the instructions for working out the number of clicks DO make sense. The instructions say to put a 10 thou feeler gauge in between the valve stem and rocker and then screw the tool down to eliminate all clearance. Then back the tool off and count the clicks until the desired feeler gauge (in this case 12 thou) can be fitted in as well as the 10 thou gauge. That is the number of clicks for 12 thou BUT it isn't the right valve clearance for that valve which would need to be done again after this initial calculation. The only thing the 10 thou feeler gauge is for is to provide a level surface to work out the clicks. From then on, feeler gauges are not used.

I did get confused and had to read the instructions several times...........

The 8 clicks as calculated mathematically is also correct and the click settings are supplied with the earlier versions of the tool but not this new one.

I should have time tomorrow afternoon to have a go. I have been too busy with work and I was away at the weekend bellringing around Cheltenham.

Stephen

[svenedin]

I still have not tried the tool out. I realised today that I do not have a 7/16" socket with 1/2" drive......A suitable socket is on order.

[svenedin]

Just to confirm that with the Gunson version of this tool, no special socket is required. A ball holds the socket in place so an ordinary 7/16" socket is secure and will not fall off. A deep socket is not suitable as the screwdriver bit would not have sufficient forward movement.

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[svenedin]

An update of this:

As mentioned earlier in this thread, I found the inlet manifold nuts to be loose and torqued them to the workshop manual spec torque. Immediately having done this the mixture seemed rich to me (exhaust smelled of petrol). I didn't change anything else. Took the car for a few runs and then inspected the plugs. They looked like this (mixture too rich but consistent across the 4):

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My thinking is that the inlet manifold was leaking air in, weakening the mixture. Once tightened up the leak stopped and the mixture became too rich.

I got out my trusty Gunson Colortune and found (not at all to my surprise) that the flame was yellow and the mixture too rich. I adjusted the carburettor mixture screw by about 5 flats leaner and the engine started to run sweeter. The flame changed to the desired Bunsen Blue.

On the valve clearance front, I had a play with the Clickadjust. It worked very nicely on some of the valves (and checking with a feeler gauge showed close agreement which suggests there is NOT severe wear) but not well at all on other valves. On the valves that played up, backing off the tool by the required (8) clicks seemed to provide no clearance at all. It seems as if something was sticking so that the adjustment had no effect. Those valves I had to adjust the standard way with ring spanner and screw driver.

So it would seem the problem was down to a leaking inlet manifold. Road tests to follow (too wet at the moment). I will also do compression tests.

Stephen

[Bill_qaz]

Great you found the solution.
You have to be careful that when you screw the tool in to get the zero check that you can still rotate the pushrod, if not you are starting to open the valve without realising. The when you back off the 8 clicks part of the clearance is lost as the valve fully closes.

[svenedin]

Great you found the solution.
You have to be careful that when you screw the tool in to get the zero check that you can still rotate the pushrod, if not you are starting to open the valve without realising. The when you back off the 8 clicks part of the clearance is lost as the valve fully closes.

Yes I think that is what happened. I will have another go with the tool when the next adjustment is due.

[Bill_qaz]

Good that you have it running better, be interesting to see what plugs look like next time you check.