inlet/ehaust valve lenght

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PFN
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inlet/ehaust valve lenght

Post by PFN »

Hi.
I'm about to finaly put my 1941 3GL engine back together. I now realize that the valves have a different overall lenght. the variation is a little more than 1/4".
These are new valves, and I don't remember from when I took it all apart if the ones i pulled out, were of different lenght. Anyone with knowledge about this. Perhaps i doesn't
matter as long as there is room in the rockerbox, and the pushrods is adjustet accordingly.
Cheers Per
SPRIDDLER
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Re: inlet/ehaust valve lenght

Post by SPRIDDLER »

It's possible that the shorter valve needs the hardened end cap.
See the illustrated Spares List. Part No. STD 685.
Here:

http://archives.jampot.dk/book/Spares_l ... st_G3L.pdf

Now renumbered as Part No. 000685 and available from Club Spares.
See here:

http://www.amoc-parts.com/store/comersu ... duct=20835
'There is a tide in the affairs of men
Which taken at the flood............'
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Rob Harknett
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Re: inlet/ehaust valve lenght

Post by Rob Harknett »

The valves were originally pt. no. inlet STD 676 Ex STD 677 new pt, no's 000676 & 000677, if they are the pt. no's of the valves you have, then they will need the caps. Some time ago I picked up a carrier bag full of NOS inlet valves and passed some on to the club spares. They may still have some.
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clive
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Re: inlet/ehaust valve lenght

Post by clive »

PFN wrote:Hi.
I'm about to finaly put my 1941 3GL engine back together. I now realize that the valves have a different overall lenght. the variation is a little more than 1/4".
These are new valves, and I don't remember from when I took it all apart if the ones i pulled out, were of different lenght. Anyone with knowledge about this. Perhaps i doesn't
matter as long as there is room in the rockerbox, and the pushrods is adjustet accordingly.
Cheers Per
if you have the earlier valves they do not have a harden end and anyway you would not get enough adjustment on the pushrods. You will need to use the end cap on the shorter valve.
clive
if it ain't broke don't fix
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Rob Harknett
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Re: inlet/ehaust valve lenght

Post by Rob Harknett »

Much earlier Clive, the 41/G3L used the same valve first introduced on the 1935 G3 & 1936 AJS onwards.
There are some longer valves about. I wonder if some manufacturers made the valves of a length, with hardened ends, to be used without the caps?
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PFN
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Re: inlet/ehaust valve lenght

Post by PFN »

Thank you gentlemen.
I have the hardened caps, that I was going to put on anyway. I quess that the lenght will not affect the traveling of the valve. I take it that the cam dictates how far the valve will open.
cheers Per
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Rob Harknett
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Re: inlet/ehaust valve lenght

Post by Rob Harknett »

I would have thought any difference in valve length will affect the tappet adjustment. So perhaps screw down the tappets if the new valve length + cap is longer than you took out, before tighten everything up. I am sure if the valve is longer, it will open a bit when you tighten up and not bend the pushrod .
PFN
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Re: inlet/ehaust valve lenght

Post by PFN »

Hello again.I have sorted it out, by obtaining two new valves, from the club spares. Equal lenght.
I now have a new problem. I have omitted the compression plate, and on assembly, I am afraid, that there is not enough room for the valves to open without colliding with the piston. I have new valve seat inserten as there were not mush material left to recut the original seats. These new seats, will enable the motor to run without the lead additive. BUT, the actual seat is now level with
The surface of the combustion chamber, and the valve head protrudes a little bit into the chamber. I have never seen a new cylinder head, and therefor have no knowledge of if this is right. With piston on tdc, and the head loosely in place, the exhaust valve have approx 5mm travel before it hits the piston top. Cam lift is measured to approx. 7.1mm, and I surpose these will also be the same where the rocker arm meets the valve stem. Im not a mathematician, but unless the pushrod side of the rockerarm is of a different lenght than the valve side arm, I think this is a fact.
Any thought on where this went wrong, or if I just worry too much.😁 Realy don't want to crash anything before I attempt a start up.
Cheers
Per
pkr87
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Re: inlet/ehaust valve lenght

Post by pkr87 »

HellonPer.One way to check the valve clearance is to assemble the engine with some modelling clay(Plasticine?) on top of the piston and by turning the engine by hand you will find how close the valves come to the top of the piston. The method I use when building race engines with fancy camshafts is to assemble the engine and set the engine with each valve at full lift then press the valves further down with a screwdriver to make sure that there is clearance between piston and valve.You might have to replace the compression plate to get the right clearance.Paul
PFN
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Re: inlet/ehaust valve lenght

Post by PFN »

Thanks Paul
I omitted the compression plate, because i read in Bernal Osborne' maintenance series, that this was a possibility, and that no chances were necessary. The cams were in the engine, when i disassembled it, so no changes there. Just new bronze bushings. If the cam have a lift of x, will the be pressed x from the seat?
I am considering to reinstall the compression plate, but I will try to find out why it wont work, before I do put it back.
I will try your method with modelling clay. Haven't thought of that myself.
Per
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