SS head combustion chamber radius

[t ingermanson]

Anyone know if the radius on the SS head's combustion chamber is constant, and if so, what the radius might be?

 

[Burgs]

Anyone know if the radius on the SS head's combustion chamber is constant, and if so, what the radius might be?

Hi not sure, but I think it would be a constant radius in that era for a Norton, Jim S has some drawings he may be able to confirm?
On a production engine at that time for Norton to produce something economically like a varying radius would be a bit of a challenge, tooling cost would in my opinion kill it at that time.
Burgs

 

[dynodave]

I see no reason that the 650 head combustion chambers are different than the original NHT. In the end they used the same 06-0380 casting and likely on the same machining center as 750's.
Currently comparing to the dunstall big valve treatement pix from a 750 head.

From an email I sent in November to a guy in France along wiht a pix of my head

The dunstall machining is the full 74mm combustion chamber but cut on a spherical 46mm radius shown in aluminum color.
The original smaller combustion diameter of 67mm and is a sphere of 42mm radius, the original combustion chamber shown in green.
4 different numbers...
The spheres do not intersect because the dunstall machining is centered on the 74mm 750 desaxe bore region and the green sphere is from the center of the original 500/600/650 combustion chamber.
This is my best guess and measurements.
dunstall head pix Attach:
big valve

 

[t ingermanson]

Thanks, fellas.

That gives me a starting place to find out. I'll report back if I find anything definitive.

One of the SS heads I have has some damage from something getting pounded into the head, inside the chamber. It'll need some filling and remachining. It's not ideal but the intakes are unmolested and all the threads are good.

 

[dynodave]

Good Luck-I have an 850 head that got beat up something fierce. it's shown on my web site...I will try a big valve conversion to use on a 74 bottom end. I have two sets of 1.650 intakes and seats. I'll try it with a 920 kit that has been on the shelf for ages...
The head has already been welded up and my friend ran a ball end mill on his CNC to clean it back up to a sphere.
A bit off topic but I also have a cracked RH4 I am going to try a 1"(or more) aluminum plug to put a new 1/2" guide in for a fix.

 

[t ingermanson]

Good Luck-I have an 850 head that got beat up something fierce. it's shown on my web site...I will try a big valve conversion to use on a 74 bottom end. I have two sets of 1.650 intakes and seats. I'll try it with a 920 kit that has been on the shelf for ages...
The head has already been welded up and my friend ran a ball end mill on his CNC to clean it back up to a sphere.
A bit off topic but I also have a cracked RH4 I am going to try a 1"(or more) aluminum plug to put a new 1/2" guide in for a fix.

When I got the head, it had a cubic-ish lump of steel wedged under the intake valve. Matches the shape and size of the divots in the head, so I reckon that's what was bouncing around.

What alu weld rod was used on that head of yours?

 

[dynodave]

RR53B is the head - It is also on the print Jim gave us
I did this welding at work - I've been retired almost 8 years and my buddy Al the welder did the head and he retired a few years before me. rod alloy ???
maybe this will help
https://www.accessnorton.com/NortonCommando/head-750-850-alloy-rr-53b.8833/

Hiduminium - Wikipedia

en.wikipedia.org