cam spec 1966 g80

Information relating to the Matchless G80 or AJS Model 18 500cc Heavyweight.
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cam spec 1966 g80

Postby DickV » Tue Oct 20, 2020 4:48 am

i have motor apart try to decide how to go forward biger carb ?
cam # 030122 intake 030123 exhaust are these touring cam is much difference g80 cs cam in same year i seen some imfo for 56 to 63 not later 65 to 69 and do cylnder head flow same

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Re: cam spec 1966 g80

Postby SPRIDDLER » Tue Oct 20, 2020 12:21 pm

DickV wrote:i have motor apart try to decide how to go forward bigger carb ?

I assume you want to increase the power of the engine.
In order to be clear I have understood your questions in this way.....

Cams # 030122 intake 030123 exhaust.
Are these touring cams much difference from g80 cs cam in same year?
I seen some info for 56 to 63 not later and 65 to 69
Do cylinder head flow same?

I don't know much about cam part numbers but you can usually identify the type by a mark stamped on the cam.

Cam marks (640x364).jpg



Have a look at this article:

http://archives.jampot.dk/technical/Gen ... _types.pdf

and also this article which refers to 'Pepping up a 500'

http://archives.jampot.dk/technical/Gen ... e_Dots.pdf

You may also be able to identify the cam numbers that you quoted by looking at G80 and G80CS models in the Spares Lists here (although there isn't much info on 1966 bikes):

http://archives.jampot.dk/book/Spares_lists/

I'm not sure exactly what you are asking about 'head flow'. :?
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Re: cam spec 1966 g80

Postby DickV » Wed Oct 21, 2020 4:37 am

hi Spriddler, thanks for your reply. I was looking for g80 scrambler cam specs, a scrambler probably has higher lift cam than touring model which I have. I find factory cams are more reliable. The article Pepping Up a 500 says a person can install a 350 lightweight engine rocker. Are these rockers available?

My other question is does a touring cylinder head flow the same amount of air as a cs Scrambler model? thanks, Dick

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Re: cam spec 1966 g80

Postby ajscomboman » Wed Oct 21, 2020 7:21 am

The cams best suited are the SH profile, available from AMC Classic Spares, or they were.

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Re: cam spec 1966 g80

Postby SPRIDDLER » Wed Oct 21, 2020 7:33 am

The scrambler cams are marked SH.

Cams hot.JPG


The only spec'n I can find for scrambler cams is valve timing up to 1962 in this workshop manual. Page 16. Fig 2

http://archives.jampot.dk/book/Workshop ... .NEILL.pdf

Cams Scrambler. Timing..JPG


I haven't checked every manual but you may find more info if you browse through the workshop manuals here:

http://archives.jampot.dk/book/Workshop_manuals/

Lightweight rockers are only available second hand as Rob mentioned and AMC Classic Spares or an auction site may help.
You could put a 'Wanted' ad on this website and the Jampot magazine,. See here:

http://www.jampot.com/Ads_Place.asp
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Last edited by SPRIDDLER on Wed Oct 21, 2020 11:19 am, edited 2 times in total.
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Re: cam spec 1966 g80

Postby SPRIDDLER » Wed Oct 21, 2020 7:59 am

DickV wrote:
My other question is does a touring cylinder head flow the same amount of air as a cs Scrambler model? thanks, Dick


I can't help with that as I've only been involved with competition tuning 2-stroke scramblers (too old to want to go faster these days). Obviously the cam profile (lift and overlap) and carb throat and inlet manifold dia. and valve head size is relevant to volume of fuel/air admitted per stroke. As you probably know the CS barrels were alloy, not that it has any influence on fuel/air flow.
If you want some ultimate nerdy info on engine breathing there's an article on induction port obstructions here:

http://archives.jampot.dk/technical/Gen ... ge_Templin).pdf

Hmm, for some reason the above link doesn't seem to work but you can find the article (Induction port obstructions) here, about halfway down the page:

http://archives.jampot.dk/technical/Gen ... al_topics/
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