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ES2 valves

Submitted by paul_gooch on Fri, 23/08/2013
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I wonder if anyone can help with a bit of a technical question.

I have recently purchased two new valves for my 1955 ES2, part number V37 on the owners club site and also on RGM motors site.

The valves appear to be around 2mm longer than the valves in the head, and 1mm longer than the dimensions quoted on George Cohen's site. He gives dimensions as between 4 and 5/32 inches and 4 and 5/16 inches, (around 105 and 109 mm respectively) My new ones are 111mm long.

All other dimensions appear OK but the diameter is a little larger than the old valves.

So....does anyone know if I have purchased dodgy repro valves, or is this difference acceptable?

Any advice gratefully received

Paul

Submitted by andy_marks on Sun, 25/08/2013

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The dimensions I have for them are:

Head Diameter: 1.725 inchs (43.8mm) Stem Diameter: 0.3715 inchs (8.1mm) Length: 4.315 inchs (109.6mm)

My understanding is that the main two issue with fitting longer valves are the tension in the spring (a longer valve would mean less tension and there for more chance of the valve bouncing), and the angle that the rocker hits the valve. You want the rocker hitting the valve square on so its not pushing the top of the valve over and increasing wear.

With a difference in length of 2mmI would have thought that would all be academic and the difference is unlikely to be noticable. But someone more knowlegeable will most likely be able to shed some more light on the subject.

Submitted by michael_sullivan on Sun, 25/08/2013

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Paul:

With the two valves standing side-by-side, where is the extra length?

Is the collet/keeper groove at the same height? Or is the groove at the same height and the extra length from the groove to the top?

Mike

Submitted by paul_gooch on Mon, 26/08/2013

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Mike, there are two mm extra between the valve seat and the collet retaining groove. The height of the top potion of the stem being the same on both valves (resulting in the new one being 2mm longer overall)

I appreciate that this will result in less tension in the valve springs when fully closed, obviously the compressed spring stages, through opening, will be within the range experienced on the shorter valve anyway. I, like Andy, was of the opinion that the extra 2mm will not significantly effect the spring rating, but wanted to seek other opinions before cutting the valve seat to accept the new valves.

I am also concered about the angle of valve clout, but again I am not convinced that 2mm overall will make a huge difference to valve wear, as the extra clearance needed is witin the range allowed for by pushrod adjustment.

I did consider taking 2mm off the end of the stem in the lathe, but was concerned this would affect the hardness of the valve stem tip.

It's easy when parts correct, and extremely annoying when they are not. I don't understand why someone going to the trouble of having new valves made up, would get the measurements wrong. Grrr

?????

Submitted by simon_amos on Tue, 01/10/2013

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Previously andy_marks wrote:

The dimensions I have for them are:

Head Diameter: 1.725 inchs (43.8mm)Stem Diameter: 0.3715 inchs (8.1mm)Length: 4.315 inchs (109.6mm)

My understanding is that the main two issue with fitting longer valves are the tension in the spring (a longer valve would mean less tension and there for more chance of the valve bouncing), and the angle that the rocker hits the valve. You want the rocker hitting the valve square on so its not pushing the top of the valve over and increasing wear.

With a difference in length of 2mmI would have thought that would all be academic and the difference is unlikely to be noticable. But someone more knowlegeable will most likely be able to shed some more light on the subject.

Hi Andy,

I think you are mixing up 3/8 and 5/16 nominal diameters:

3/8 nominally is 9.53 mm

5/16 is nominally 7.95mm

Give or take a bit.

So : Stem Diameter: 0.3715 inchs would be 9.43mm not 8.1mm

I am not trying to be smart - I am in engineering and I am doing the same thing often when converting in my head so am not imune to the mistake- but it is worth pointing out just to avoid confusion for those who are not well versed in measurement.

Submitted by neil_wyatt on Tue, 01/10/2013

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I was just about to say not to confuse the 5/16 with the 3/8 but Paul beat me to it. But while on the topic, don't forget to make sure your exhaust valve is non magnetic, unless you want to replace it at a regular interval. I got mine from G&S valves' or something like that from memory, many years ago and are made to perfection in stainless.

Submitted by andy_marks on Wed, 02/10/2013

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Hi

Sorry about that. Not sure how I managed to get them mixed up, must have been a long day! I've ordered some new valves for my ES2 that should be here any day now. I'll have a measure up of them and make sure I double check my info before posting :)

Submitted by andy_marks on Wed, 02/10/2013

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0.3175 is 8.1mm. Looks like I got the 1 and the 7 the wrong way round when I typed it into the calculator.

The valve stem should be 0.3715, which as you said is 9.43mm. This gives 0.0035 clearance between the valve and the 0.375 bore guide.

Must double check my maths next time!

 


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