Spigott barrel warped

J

Jan Huss

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I am trying to locate an oil leak on my 650SS and found that the upper barrel sealing surface (barrel-to-head) is warped. It is concave and in the pushrod tunnel area a 0,05mm feeler gauge fits under a straightedge placed across the surface. Additionally, the sealing surface looks quite rough, as if made with a rough file. The head surface, in contrast, is perfectly straight and smooth. Simply grinding down the barrel surface on a flat surface is not possible because of the protruding spigots. I researched the internet on that issue and found that other people apparently also found concave barrel surfaces on their Nortons, however I could not find any conclusions on this matter. Hopefully someone has experience with this situation and can answer my questions:
1. Is a concave barrel sealing surface a common issue? It´s hard to imagine that a cast iron cylinder block will distort that way- what happened? Or did it leave the factory like this?
2. does a composite gasket (maybe with additional sealant) seal a 0,05mm gap?
3. what can be done to straighten the sealing surface? Maybe filing or scraping around the spigots?

thanks for any advice

Jan
 
Maybe take it to someone with a mill to machine the top surface, until it is "clean" and parallel with the base?
I hand-scraped the base of my 650ss barrel to reduce the gaps from .006" to .001" so as to not need a base gasket.
Hand scraping is hard yakka, with lots of blueing in between!

BTW - how good is your base?
Cheers
 
Jan Huss said:
I am trying to locate an oil leak on my 650SS and found that the upper barrel sealing surface (barrel-to-head) is warped. It is concave and in the pushrod tunnel area a 0,05mm feeler gauge fits under a straightedge placed across the surface. Additionally, the sealing surface looks quite rough, as if made with a rough file. The head surface, in contrast, is perfectly straight and smooth. Simply grinding down the barrel surface on a flat surface is not possible because of the protruding spigots. I researched the internet on that issue and found that other people apparently also found concave barrel surfaces on their Nortons, however I could not find any conclusions on this matter. Hopefully someone has experience with this situation and can answer my questions:
1. Is a concave barrel sealing surface a common issue? It´s hard to imagine that a cast iron cylinder block will distort that way- what happened? Or did it leave the factory like this?
2. does a composite gasket (maybe with additional sealant) seal a 0,05mm gap?
3. what can be done to straighten the sealing surface? Maybe filing or scraping around the spigots?

thanks for any advice

Jan
Click to expand...
A good engineer with a decent mill could sort that for you
Or get the spigots machined off and the top of the barrel resurfaced
 
My N15 came with rings to take the place of the spigots. I believe the factory use them so heads that had been machined to use on spigot barrels now could be used on the non-spigot barrels. These sit in the head. They are factory parts and I had seen them listed before, but now I can't find them, at Andover Norton at least.
 
Last edited:
Do they even make a composite gasket for a spigot head?

You cou could try pilobond glue and thin copper wire.
I'd try that before anything else.
It has been written about on here before.
 
Last edited:
robs ss said:
Maybe take it to someone with a mill to machine the top surface, until it is "clean" and parallel with the base?
I hand-scraped the base of my 650ss barrel to reduce the gaps from .006" to .001" so as to not need a base gasket.
Hand scraping is hard yakka, with lots of blueing in between!

BTW - how good is your base?
Cheers
Click to expand...
the base flange is good, no problems there. I need to find someone who can mill around the spigots, not just an ordinary job...
 
elefantrider said:
Do they even make a composite gasket for a spigot head?

You cou could try pilobond glue and thin copper wire.
I'd try that before anything else.
It has been written about on here before.
Click to expand...
yes, I read about this method and I will definitely try this before milling the spigots off. Question is, up to which size gap will it seal? I think I just have to try.
 
franko said:
rings are shown in post number six of this thread.
The rings from the same thread
www.rgmnorton.co.uk

ALLOY RECESS RING FOR CONVERTING SPIGOTED CYLINDER HEAD TO NON SPIGOTED

ALLOY RECESS RING FOR CONVERTING SPIGOTED CYLINDER HEAD TO NON SPIGOTED OUTSIDE DIAMETER: 3 1/8" (79.4MM)INSIDE DIAMETER: 2.924" (74.25MM) DEPTH:
www.rgmnorton.co.uk
Click to expand...
I think this is an option as a "last resort" , and I know that later 650s and 750s came without spigots anyway. But I would prefer to leave the spigots in place...
 
The copper wire is available in different thicknesses, and you do both the head and the barrel sides.
I have a theory the spigots were done to help sealing before good head gaskets. I do not know for sure.
Have both types.
 
I am curious as to whether the purpose of the spigots was for sealing or was it for registration of cylinder head . I have a set of barrels for a dynamo Model 99 that has a chip out of one of the top spigots and don’t know how this will affect operation.
 
Good luck finding someone to do that on a machine. I'd just try sealant and copper wire. You're really only sealing up for oil leaks. With the spigots, I think you have better protection against a blown head gasket, so it is less important to have a flat surface. WIll post some links.
 
elefantrider said:
Good luck finding someone to do that on a machine.
Click to expand...
This is an operation well within the skill of any local manual machine shop and requires the skills of an average apprentice. A Bridgeport, a rotary table, a 1/2" end mill, a handful of 123 blocks, a couple hours, and done. It certainly doesn't need to be a Norton specialist, nor does it require special tools.

I would try and talk myself into NEEDing a Kearney and Trecker 2D rotary head mill, but I've been trying to convince myself of that for decades, but it's a hard sell.

Perfect is the enemy of good enough, but putting an aluminum head through (hopefully) infinite heat cycles while tightly clamped to a banana shaped barrel is not optimal. Who knows what you're transferring to the guides/valves/seats, rocker spindles, etc. It's the "foundation of your house", and adds or removes a lot of complicating factors.

Just my dos centavos.
 
t ingermanson said:
This is an operation well within the skill of any local manual machine shop and requires the skills of an average apprentice. A Bridgeport, a rotary table, a 1/2" end mill, a handful of 123 blocks, a couple hours, and done. It certainly doesn't need to be a Norton specialist, nor does it require special tools.

I would try and talk myself into NEEDing a Kearney and Trecker 2D rotary head mill, but I've been trying to convince myself of that for decades, but it's a hard sell.

Perfect is the enemy of good enough, but putting an aluminum head through (hopefully) infinite heat cycles while tightly clamped to a banana shaped barrel is not optimal. Who knows what you're transferring to the guides/valves/seats, rocker spindles, etc. It's the "foundation of your house", and adds or removes a lot of complicating factors.

Just my dos centavos.
Click to expand...
you are right, an even sealing surface is of course the best option. And luckily I just found someone who is willing to do the machining and has the right equipment!!! So, this will be the way to go.

Thanks,

Jan
 
Richard Tool said:
I am curious as to whether the purpose of the spigots was for sealing or was it for registration of cylinder head . I have a set of barrels for a dynamo Model 99 that has a chip out of one of the top spigots and don’t know how this will affect operation.
Click to expand...
I don't know on the twins but on singles the spigot is the seal, from memory it is about 2 thou taller than the head recess and bruises into it when the head is torqued down. Others may know whether that is how twins worked as well?
 
ntst8 said:
I don't know on the twins but on singles the spigot is the seal, from memory it is about 2 thou taller than the head recess and bruises into it when the head is torqued down. Others may know whether that is how twins worked as well?
Click to expand...
I also have single engines with spigots. This was (is?) quite common for example on 2-stroke offroad bikes. On my '83 Husqvarna I could lap the cylinder head on the spigot by rotating the head back and forth with grinding paste. It sealed perfectly, no gasket needed.

On a twin you can´t rotate the head on the spigots for lapping, so I can´t think of a way to get a proper seal there. Also, there might be insufficient pressure on the gasket once the spigots are bottoming out in the recesses. I think on a twin the spigot has to be shorter than the depth of the recess so that when you are torqueing down the head the gasket receives the correct pressure.

...or am I wrong???
 
Jan Huss said:
I think on a twin the spigot has to be shorter than the depth of the recess so that when you are torqueing down the head the gasket receives the correct pressure.

...or am I wrong???
Click to expand...
You are right. The compression sealing shoud be at the top deck of the barrel and the corresponding surface of the cylinder head. If the head's surface has been trued, the spigot recess needs to be machined as well for a small clarance to the spigot when bolted up.

- Knut
 
mdt-son said:
You are right. The compression sealing shoud be at the top deck of the barrel and the corresponding surface of the cylinder head. If the head's surface has been trued, the spigot recess needs to be machined as well for a small clarance to the spigot when bolted up.

- Knut
Click to expand...
So the primary purpose of the spigots on twins is for registration?
Or is it to take some of the load off the head gasket by putting up a wall ?
 

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