Alloy heads and copper gaskets.

[greg brillus]

Hi there all, Does anyone know if the alloy head singles used a copper gasket between the head and barrel..........The TTR I have here had one in place, I tried to set up the head/barrel so it did not need it, but i can't stop the joint leaking........So the copper gasket may have to be annealed and put back again..........Cheers........ Greg.

 

[A Nut]

Hi Greg,
My bike has a bronze head but as it has a shortened barrel I decided to put an annealed copper gasket on it and have had no trouble. I had to have the seats welded up and that caused some distortion in the head so after re machining I then ground the head onto the barrel as per the post war setup.
Cheers
Brian

 

[Marvel]

Hi Greg,
My bike has a bronze head but as it has a shortened barrel I decided to put an annealed copper gasket on it and have had no trouble. I had to have the seats welded up and that caused some distortion in the head so after re machining I then ground the head onto the barrel as per the post war setup.
Cheers
Brian

Hi Brian,
Who did you get to weld your bronze head? I have one on my Comet that needs the same and can't decide whether to weld or put inserts in.
Cheers Neil

 

[greg brillus]

I removed the head off this engine, cleaned it all up, and reinstalled the copper gasket. I annealed it first and coated it in VHT copper gasket spray.........I have since ran it several times and ridden it about 3 times over the last week or so. Despite it having a 46 tooth rear sprocket, the bike goes like a rocket..........Interestingly I put it on the scales and it came in at 160 Kg's wet..........I did make some of the hold down studs longer so i could use hardened washers under the nuts, this made removing/installing the head quite difficult, but the extra stud/thread length was worth it.

 

[A Nut]

Hi Brian,
Who did you get to weld your bronze head? I have one on my Comet that needs the same and can't decide whether to weld or put inserts in.
Cheers Neil

Hi Neil,
Over the years I have had 2 bronze heads welded up but many years ago by a specialist welder near Cirencester. Unfortunately he has long retired. The one on my Comet went quite well but the other on the TT bike not so well. This head had valve seats fitted by a so called specialist but the problem was (and is) that there is hot enough meat there to sink a valve seat in and consequently even with a shallow seat the seats eventually broke through into the ports. This head had to have extensive welding as the seat cavities had to be filled as well. On machining I found that there was not quite enough weld deposited so it had to he rewelded. The heat involved distorted the head and I had to reface it and also rebore and align the valve guide holes. Unfortunately I don't have an answer for you except that I think you may be safer going down the welding route but you will need to find a specialist.
Best of luck
Brian

 

[Nulli Secundus]

Hi Neil,

You could try Exactweld GB Ltd, Unit J, Charlwoods Business Centre, East Grinstead, RH19 2HH for bronze welding.

Tel: 01342 311595

I cannot make a personal recommendation but I have heard many good reorts about them. A VOC friend has used them for welding the bronze head on his Rudge Ulster.

As it happens the same friend is doing an intricate repair on my TTR Rudge crankcase. It was decided, after much thought and deliberation, that the crankcase needing welding to repair the thrust main bearing lock ring thread that is between the two drive side main bearings.

He had the crankcase delivered to Exactweld and it looks like they did a good job. I have only seen a photo of the repair and not seen the repair in the flesh.

Good luck

David

 

[Marvel]

Hi Neil,
Over the years I have had 2 bronze heads welded up but many years ago by a specialist welder near Cirencester. Unfortunately he has long retired. The one on my Comet went quite well but the other on the TT bike not so well. This head had valve seats fitted by a so called specialist but the problem was (and is) that there is hot enough meat there to sink a valve seat in and consequently even with a shallow seat the seats eventually broke through into the ports. This head had to have extensive welding as the seat cavities had to be filled as well. On machining I found that there was not quite enough weld deposited so it had to he rewelded. The heat involved distorted the head and I had to reface it and also rebore and align the valve guide holes. Unfortunately I don't have an answer for you except that I think you may be safer going down the welding route but you will need to find a specialist.
Best of luck
Brian

Hi Brian,
This is what I've always thought about fitting seat inserts, that there isn't enough depth to accommodate them especially on the exhaust port. I recall Dad had inserts fitted in one of the bronze heads one of which fell out and he had the seats welded. I've still got the receipt somewhere but now I need it I can't find it. It was nearly 50 years ago!

Hi David,
Thanks for the link. I will definitely contact them. The head needs some machining first to make the bottom valve guide hole concentric and square to to the top guide hole after the valve guide came loose and wore the hole oversize. Once this is done and the seats welded the seats can be re-machined.

Thanks for your help.

 

[Marvel]

I had the valve seats in my bronze head laser welded by EMP Tooling in Havant. The head was then set-up locating off the top guide and the bottom guide hole machined square and concentric to it. New bottom guides were machined with the bore undersize then finished square and true to the top guide. The valve seats were machined true to the guides. When all the machining was done the excess weld was removed. Hopefully I'll never have to do it again. I read somewhere that unleaded petrol is better for bronze heads. Can anyone confirm this?

 

[oexing]

Yes, Marvel, that seems to be the case with leaded gasoline on bronce heads. I had a report of a Tiger Moth owner who over years had troubles with exhaust seat wear in bronce head from having to use leaded avgas. When these Moths were new, prewar, they had no lead in fuel so no worries. But in last decades he had to tank avgas 100 LL with consequences.
The alternative of getting unleaded fuel for his aircraft had the calamity of the aggressive thinner containing modern fuel acting on hoses and more seriously on the painted cork carb float he would not want to endanger. So he is in a bad situation in either choice, don´t know how he decided.
I think the process of wear on bronce seats is a bit like wear on soldering irons, in fact the copper heads on these, when exposing them to a ton of lead containing soldering wire. That is the reason why the competent brands of soldering irons have the tips coated with iron based or the like for durable protection from copper loss.

Vic

 

[Vincent Brake]

Hi Brian,
Who did you get to weld your bronze head? I have one on my Comet that needs the same and can't decide whether to weld or put inserts in.
Cheers Neil

I would go inserts.
Made from Ampco 45. Or so.
Easy to do with a hunger cutter.