Valve Seat Inserts

the 'normal suppliers' don't have them, as it is unlikely anyone outside of a professional concern would have the equipment to change them. 

I suggest you contact someone like SRM in Wales who were one of the first to offer 'unleaded seats' for bikes and have a very good reputation in the BSA world and do a lot of Norton stuff too.

https://www.srmclassicbikes.com/engineering Not used them myself and have no connections.

Alternatively, have you asked the shops if they can do it or just looked at the websites? If they can't do it, I'm sure they would advise you on where the good places to go are (and more importantly may well know where to avoid!)

Good Luck!

George

I have no idea how good of a job SRM do, but they seem to have a certain way of doing business, I sent a late dommy head to them for new exhaust valve seats to be fitted.They quoted me just short of  £500 which included  new inlet seats, and new valves and guides all round. I contacted them and pointed out that I only wanted new exhaust seats fitting, that the inlet ones were ok anyway, and that I could do the rest myself, to which their reply was, more or less "We don't do that, this is how we do it, take it or leave it", so I said leave it and had to pay  quite a sum to have my head sent back not done, and found another one with good seats for less than £100.

So if you go to SRM be prepared to have the lot done.

The Atlas seats looked pocketed  ,but checking the rocker action accross the valve tip. . all looked good. Its clear that the action from new was not the best ,but it seemed that it had fixed itself !. I got my local engineer to unmask the valves with his cutters and  it all looks ok.  Runs fine too. Later motors got longer valves to improve the action ,so AMC  knew something was not the best.

With  the Atlas valves now set further into the head I did not consider that  the valve spring pre-load is a bit reduced. But knowing how the bike is used,  tractor fashion ,high revs is never going to happen and the cam will be happy with its easy life in old age.

Hi Steve,

I spent my working life developing and calibrating car engines, so I have a fair understanding of what is required here.

Personally I wouldn't touch them. Worst case scenario is head gets damaged such that pockets need enlarging deeper or bigger diameter which could/will weaken the head. Please talk to the machine shop you wish to use as to whether this will save you a fortune or make their job harder first!

Of course, it is your head. If you do want to get them out, I suggest you mill out as much of the seat as you can and you might just be lucky that they will crack and fall out. (they  are austenitic cast iron if the original seats.) 

You never know, you may just find that they aren't as bad as they look and not need changing? Are you looking for that last 1-2 bhp? I remember finding out years ago that the valves and seats will 'pit' quite quickly - certainly within a couple of hours running! 

Best Regards,

George 

If the seats are badly pocketed then there are 2 cheap fixes worth trying before having the seat renewed.

1. Bigger valves, these will sit further up on the unworn part of the seat and then cut on the bigger diameter.

3. Use a set of 3 angle seat cutters and first cut away on the shallow angle to unshield the valve followed by light cuts and the remaining 2 angles. 

My PO inserted seats himself. I have no idea now what material he used, but valve grinding paste has no effect whatsoever on them.

I remember he said he heated the head and chilled the seats. But now they are together it must be difficult to heat or cool one without the other. But it might be possible to heat the head as if for valve guide changing, and push a bag of ice...or, better  'dry ice'...in the aperture and see if they just fall out.  Where to get dry ice? Pipe freezing kit maybe?

The norton head print states the seats are shunk fit.... not cast inI have done several seat changes. The head is oven heated to around 400f and the seat AND the inserting tool are chilled in dry ice (CO2). Using the old guide to guide the insertion tool, you have two rapid hits with the hammer and it better be "home". or take it out and start over.

This is what I do to remove the old seats....

Grind the head of an old valve until it just slides down inside the valve seat. Weld a bead around the inside of the seat. Let cool and then tap the valve stem until it comes out."  Steve

The original alloy is excellent even for eventual no lead fuel. I buy mine from machine shop supply houses. But you buy them in a box of 10. I had gotten the big seats and 1.6 valves from Norvil a long time ago. These industrial supply places are not usually interested in sales to hobbyists.

For my own Lotus elan head I will have to buy +10 and grind them down to +5 my self as they sell standard over sizes only.

I had the very recessed (85,000 miles) valve seats on my 650SS head changed for unleaded versions 35 years ago. After running the bike for a month the head gasket blew and needed replacing. The head had warped due to the extreme heat used in swopping the seats. This was skimmed to correct but at the same that time the bent head was being sorted it was very obvious that the valve heads were picking up on the new seats and leaving serious craters. The valves were changed for some that had more Chrome in them but these, in turn, took out the valve guides.  These were replaced for Colisbro versions and all has well since.

It would be handy if somebody, versed in Metallog,y could list the best combinations of materials for the cylinder head valves, guides and seats to use with unleaded,  Ethanol loaded fuel.

1. alloy is RR53B

2. If you heat the head enough to have the seats "drop out" then I would certainly expect the head to twist up.

3. I have yet to need to mill/skim a NHT head. I do check them all, with machinist dye and burnished on my surface plate.

My first combat head was turned over for a valve job to a profe$$ional shop. They of course knew nothing of nortons and promptly ruined the exhaust seats. They happily turned the head back over to me unfinished.

Out of that came one of my sayings...Why pay someone to ruin my stuff when "I" can ruin it for "free".

So after 30 years with thousands of dollars of tools and equipment and a lot of experience on norton heads of my own and club friends I have almost paid off all my equipment and gotten a darn good education.

Here in the US there are still a few (very few) sources for NO-E fuel but for the most part all machine work and parts is done to be E-10 capable.

Only the model 7 iron heads are needing special work.

Interesting about the alloy.  The tensile strength as cast is relatively low, and it's easy to machine.  It's much stronger after heat treatment (artificial aging) but they would surely not have heat treated after machining.  But the kind of temperatures people talk about here might well have done the job. You'd end up with a stronger cylinder head, but its crystal structure and thus shape changes....

Valve seat room temp 1.505 

seat and tool @ dry ice/ -78.5C    1.5025

head room temp 1.4995   @ oven 400f  1.506

seat @ 400f  1.5072

I remember many years ago when leaded fuel was being phased out that they said alloy heads (with hardened valve seat inserts) didn't need replacing.  This was particularly for car engines like my Jaguars, which have a lot of valves and seats!   It may well depend on mileage where seat recession could become a nuisance, but that would be for high mileage (20k+ per year) business and commuter use.

They are unleaded proof out the box but if worn or damaged they do need replacing.

So these sound like they do

The seats are pretty bad