G3L G3LS head identification

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Honest Harry
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Joined: Mon Aug 07, 2017 8:36 pm
Location: NORTH YORKSHIRE UK

G3L G3LS head identification

Post by Honest Harry »

I have just bought a couple of Matchless 350s from a deceased estate (one is a mixture of late '40s, early 50's and the other a mixture of '50s in a 61 chassis but with a 61 engine number) plus a load of spares.

I am wanting a bit of advice regarding identifying some of the spares. Both of the bikes have a valve lifter yet among the spares are 5 rocker boxes which seem the same as the ones on the bikes but none have a valve lifter. Was the valve lifter only fitted on certain years or models.
Cylinder heads. 4 cylinder heads which all match re stud holes, valve and port sizes etc but with one main differance. 2 of the heads are the same as the 2 on the bikes as in the push rod tubes meet the head 3 fins up but on the other 2 heads the push rod tubes meet the head at the mating face.
Any clues as to years for the 2 differant heads? Are they still G3 heads and would these be a straight swap for the others assuming shorter pushrod tubes were used?

Regarding the bike with the late '40s frame. I presume this would have had an iron head and rear mag when built. It now has an alumiium head and front mounted mag. It also has an advance and retard bulge on the timing cover but an advance and retard lever. Bit of a puzzle there until I take the cover off to see if an a/r unit is actually fitted.
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Rob Harknett
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Location: ESSEX UK

Re: G3L G3LS head identification

Post by Rob Harknett »

The bulge timing cover for 350 is 1955 onwards with SR1 mag which had auto advance. You should easily see if the mag is SR1, if it is not SR1 it will be an older type requiring AR lever. You should also see where the cable fits the mag, which is absent on an SR1 mag. So no need to remove the timing cover to see if it has auto advance and needs an AR lever. It will need a similar air lever what ever mag is fitted.
Honest Harry
Posts: 2
Joined: Mon Aug 07, 2017 8:36 pm
Location: NORTH YORKSHIRE UK

Re: G3L G3LS head identification

Post by Honest Harry »

Hi Rob. Thanks for that but it doesn't really tell me anything new. The main query was the cylinder heads.
The 1961 model has had a mag retrifitted and this is an SR1 with auto advance The earlier model has manual a/r but still the bulge in the timing case. As this is the wrong timing case it is probably just a matter of someone fitting what was available. All of that I had already either figured out , surmised or knew.
Any advice on the heads and rocker boxes would be welcome though
SPRIDDLER
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Location: WEST SUSSEX UK

Re: G3L G3LS head identification

Post by SPRIDDLER »

Harry.
Have a read of this article which discusses the development and (reasons for) changes to the Heavyweight 350/500 engine, including the cyl head material and relocation of the valve lifter from crankcase to rocker box when the alloy head was introduced.

http://archives.jampot.dk/editorial/Roa ... _Baker.pdf

The illustrated Spares Lists for all models will help you identify parts/years and can be found here:

http://archives.jampot.dk/book/Spares_lists/
'There is a tide in the affairs of men
Which taken at the flood............'
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