Roll out the barrel

thomthom · Post by **thomthom** » Sun Jan 13, 2008 4:18 pm

I have just removed the cylinder heads and barrels from my 1960 G12 DL, all part of an overhaul not due to any noted problem.
The barrels have a short spigot on the top where they enter their cyl. head and a long spigot on the bottom which enters into the cranckcases.

The approx. spigot dia sizes in mm are as follows:-
,,,,,,,,,Upper,,,,Lower
RH,,,,,,,77.7,,,,,79.2
LH,,,,,,,76.2,,,,,79.2

Both pistons are “plus30”. There is no evidence of any ‘blowby’ on the head gasket and both L&R gaskets were a tight fit around the spigot when they were removed. Both cyl. hds. are the same size iwo the barrelsand a snug fit on the larger spigot.

Where the cylinder barrels and gaskets made in different sizes for the same capacity engines.

TommoT · Post by **TommoT** » Sun Jan 13, 2008 5:04 pm

What is the question

thomthom · Post by **thomthom** » Sun Jan 13, 2008 5:11 pm

Sorry can't rite inglish

Where Were the cylinder barrels spigots and gaskets made in different sizes for the same capacity engines ?.

Eric · Post by **Eric** » Sun Jan 13, 2008 5:11 pm

1960 onward the twin engines were only made as 500 cc and 650 cc with different pistons and heads to those of earlier years. Looks as though the bore sizes remained the same throughout the years with different sizes for 500, 600, and 650 the barrels were also longer for the longer strokes used on 600 & 650. Later still the securing studs changed from 5/16" to 3/8" dia and even later the Norton engine was used.

Don Madden · Post by **Don Madden** » Sun Jan 13, 2008 5:13 pm

1959 8 fin barrels for the 650cc had an upper spigot diameter of 3.00in, (76.2mm), same as the 600cc barrels.

1960-up 650cc barrels have a diameter of 3.060in, (77.7mm). Looks like you have one of each. Check the height of the cylinders carefully to be sure they match, as I've seen some that didn't.

Cheers, Don.

thomthom · Post by **thomthom** » Sun Jan 13, 2008 5:28 pm

Don,

thanks

Just been out to the garage in the wind and rain to check.

8 Fins each, the LH is 76.6 & the RH is 76.7 in height from the landing face of the barrel to crankcase to the upper face for the cylinder head.

Do you know what the difference in the heights of 59/60 wereEdited by - thomthom on 13 Jan 2008 5:39:08 PM

Biscuit · Post by **Biscuit** » Sun Jan 13, 2008 5:52 pm

Just to inject my two pennorth, 500's and 600's shared the same stroke, the bores were different.

If your 77.6 and 77.7 are those stupid millimetres, then unless my calculations are wrong .1mm equates 4 thou. What's the problem?

thomthom · Post by **thomthom** » Sun Jan 13, 2008 6:25 pm

The height was not an issue, I gave those dimensions for clarity in reference to Don's caution wrt variations in height. The upper spigot outside diameter was the original question and I think that it has been answered.

wrt “those stupid millimetres”. I guess your comment was tongue in cheek. I started my career and education with the imperial system and gradually moved towards the metric system. Most of the equipment that I worked with initially was made in GB but latterly it mostly came from Europe/Japan and any that still came from GB was dimensioned in the metric system. Albeit often converted from imperial design sizes. I still use both systems and they both have their place in engineering. AMC often referred to the metric system when pistons, barrels and capacity were concerned, you even mention 500’s and 600’s yourself.

itma · Post by **itma** » Sun Jan 13, 2008 7:13 pm

For myself I have no problem with either metric or imperial measurements, I am equally confused and inaccurate with both systems.

Biscuit · Post by **Biscuit** » Sun Jan 13, 2008 7:37 pm

By common usage bore, stroke and capacity, plus sparking plug threads have always been expressed in metric dimensions. I freely admit I am an anachronism, to me the metric system is cumbersome, but 12" to 1 foot may be cumbersome to others.