Removing cylinder spigots

Previously malcolm_begg wrote:

Is their any problems in removing cylinder spigots as they were cracked,I've had the head skimmed, do I need a special gasket?

Thanks

why did you have the head skimmed , and why have the spigot cracked , some one most of over bored the barrel to get cracked spigots, Norton had spigots in place for a reason and this was to stop the cylinder head from blowing gaskets so now you need and composite gasket and Stag wellseal . good luck as you need it, yours anna j

Previously malcolm_begg wrote:

Is their any problems in removing cylinder spigots as they were cracked,i've had the head skimmed, do I need a special gasket?

Thanks

RGM's head gasket for non spiggoted barrels Part No. 067920

Previously anna jeannette Dixon wrote:

Norton had spigots in place for a reason and this was to stop the cylinder head from blowing gaskets so now you need and composite gasket and Stag wellseal . good luck as you need it, yours anna j

Norton themselves done away with the spigots on all later engines as apparently they had a tendancy to crack on the 750's & they realised they were un-necessary. According to the 1996 NOC year book, from engine number 114870. For heads that had been machined to accept the spigot, they provided ally rings to fill the gap, thus keeping compression ratio's the same, on later heads they didn't machine the recess. You need a gasket with a flame ring or a solid copper item & if you don't have the rings you will simply drop the compression ratio a bit, but having had it skimmed, you will gain a bit of that back. I've seen more than one engine with no rings fitted & still running & performing quite happily. (I took one engine appart & found a ring in one cylinder, but not the other & it had been running like that for years!) If you have to resort to Wellseal to stop it leaking, something is wrong!

Regards, Tim

The spigots on the big twin motors are quite fragile and it is common for them to fail once a barrel has been rebored to 40 thou or beyond. As others have pointed out, if removed, they will cause a slight loss of compression due to missing metal.

On the Atlas engine, after the spigots were removed, factory gaskets had more meat in the bore area to compensate. I don't recall this happening on the 650 engines though some specialist Norton parts suppliers did offer such gaskets for a short while.

I am always a little worried when owners mention skimmed cylinder heads. People forget that if a lot of metal is removed then you are going to bring the valve heads much closer to the piston tops. Tap Tap Tap!!!

Tap, tap, tap: Makes me wonder if this is the problem with my 650? Big end is still favourite but will let you know on the appropriate thread before the end of summer. (God Willing)

Hi all,

Interesting thread! I have a Norton Mercury 650 which has no spigot, but it has the recess in the head. Though it was easy to kick-over! Compression is probably down on what it should be. Does anybody know whether the alloy rings that Tim mentioned are still available?

Best regards,

Chas

Previously anna jeannette Dixon wrote:

Norton had spigots in place for a reason and this was to stop the cylinder head from blowing gaskets so now you need and composite gasket and Stag wellseal . good luck as you need it, yours anna j

Norton themselves done away with the spigots on all later engines as apparently they had a tendancy to crack on the 750's & they realised they were un-necessary. According to the 1996 NOC year book, from engine number 114870. For heads that had been machined to accept the spigot, they provided ally rings to fill the gap, thus keeping compression ratio's the same, on later heads they didn't machine the recess. You need a gasket with a flame ring or a solid copper item & if you don't have the rings you will simply drop the compression ratio a bit, but having had it skimmed, you will gain a bit of that back. I've seen more than one engine with no rings fitted & still running & performing quite happily. (I took one engine appart & found a ring in one cylinder, but not the other & it had been running like that for years!) If you have to resort to Wellseal to stop it leaking, something is wrong!

Regards, Tim

cyl .head rings. Norvil part no.990613 [for 600/650] but be sure to loctite them in and shield them with RGM's head gasket Pt No.067920 otherwise they'll be blown to bits in no time!

Hi all,

Interesting thread! I have a Norton Mercury 650 which has no spigot, but it has the recess in the head. Though it was easy to kick-over! Compression is probably down on what it should be. Does anybody know whether the alloy rings that Tim mentioned are still available?

Best regards,

Chas

Previously anna jeannette Dixon wrote:

Norton had spigots in place for a reason and this was to stop the cylinder head from blowing gaskets so now you need and composite gasket and Stag wellseal . good luck as you need it, yours anna j

Norton themselves done away with the spigots on all later engines as apparently they had a tendancy to crack on the 750's & they realised they were un-necessary. According to the 1996 NOC year book, from engine number 114870. For heads that had been machined to accept the spigot, they provided ally rings to fill the gap, thus keeping compression ratio's the same, on later heads they didn't machine the recess. You need a gasket with a flame ring or a solid copper item & if you don't have the rings you will simply drop the compression ratio a bit, but having had it skimmed, you will gain a bit of that back. I've seen more than one engine with no rings fitted & still running & performing quite happily. (I took one engine appart & found a ring in one cylinder, but not the other & it had been running like that for years!) If you have to resort to Wellseal to stop it leaking, something is wrong!

Regards, Tim

When the subject of cylinder spigots came up, John Hudson always used to shake his head and say "I'll never know why Woolwich did away with them. Bracebridge Street would never have done such a thing..."

To be honest though, he used to say that quite a lot about AMC..

Thanks for info Terence, will order parts ready for next strip down.

Best regards,

Chas:

cyl .head rings. Norvil part no.990613 [for 600/650] but be sure to loctite them in and shield them with RGM's head gasket Pt No.067920 otherwise they'll be blown to bits in no time!

Hi all,

Interesting thread! I have a Norton Mercury 650 which has no spigot, but it has the recess in the head. Though it was easy to kick-over! Compression is probably down on what it should be. Does anybody know whether the alloy rings that Tim mentioned are still available?

Best regards,

Chas

Previously anna jeannette Dixon wrote:

Norton had spigots in place for a reason and this was to stop the cylinder head from blowing gaskets so now you need and composite gasket and Stag wellseal . good luck as you need it, yours anna j

Norton themselves done away with the spigots on all later engines as apparently they had a tendancy to crack on the 750's & they realised they were un-necessary. According to the 1996 NOC year book, from engine number 114870. For heads that had been machined to accept the spigot, they provided ally rings to fill the gap, thus keeping compression ratio's the same, on later heads they didn't machine the recess. You need a gasket with a flame ring or a solid copper item & if you don't have the rings you will simply drop the compression ratio a bit, but having had it skimmed, you will gain a bit of that back. I've seen more than one engine with no rings fitted & still running & performing quite happily. (I took one engine appart & found a ring in one cylinder, but not the other & it had been running like that for years!) If you have to resort to Wellseal to stop it leaking, something is wrong!

Regards, Tim

Previously richard_payne wrote:

When the subject of cylinder spigots came up, John Hudson always used to shake his head and say "I'll never know why Woolwich did away with them. Bracebridge Street would never have done such a thing..."

To be honest though, he used to say that quite a lot about AMC..

Thats interesting, as in the same NOC year book that I took the engine number info from, John Hudson is quoted as saying that when he was testing at Birmingham, they tested 88 & 99 models with spigotless barrels & found them to be perfectly satisfactory, with no problems but despite this, the designers felt it better engineering practice to retain them.

Funny old world

Regards, Tim

It must be my memory then Tim. I usually came across John at NOC rallies and events where alcohol was widely available. I was probably really drunk at the time...