Soft in the Head.

Greetings all,
After a great old catch up and reminisce with an old old mate recently, that still races Classic Motocross,
I thought I should raise this topic........
He recently purchased yet another Norton Wasp Outfit, and was told by the P/O that he was having alsorts of
trouble keeping the head tight.
When I say alsorts of trouble, I mean, he ( the P/O ) replaced Head gaskets, machined the head and barrels etc, but couldn't
keep the thing tight.
Long story short, In the end, the new owner found that the Studs were actually pulling down into the head or,
that the Head was pushing up around the bolt heads, if you like.
Soft Head.
Being a 920, I guess that means that it was originally an 850.
Has any one heard of this before. ?
He has machined around the holes to allow for a larger washer, which at this stage has worked.
AC.

AussieCombat said:

Greetings all,
After a great old catch up and reminisce with an old old mate recently, that still races Classic Motocross,
I thought I should raise this topic........
He recently purchased yet another Norton Wasp Outfit, and was told by the P/O that he was having alsorts of
trouble keeping the head tight.
When I say alsorts of trouble, I mean, he ( the P/O ) replaced Head gaskets, machined the head and barrels etc, but couldn't
keep the thing tight.
Long story short, In the end, the new owner found that the Studs were actually pulling down into the head or,
that the Head was pushing up around the bolt heads, if you like.
Soft Head.
Being a 920, I guess that means that it was originally an 850.
Has any one heard of this before. ?
He has machined around the holes to allow for a larger washer, which at this stage has worked.
AC.

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I have seen that on heads that have been overheated by welding. In fact I have caused that by welding in the chambers. It is very difficult to weld on a head beyond fin repairs without affecting the hardness. Washers will fix it for a while but they are difficult to keep straight after they have been annealed. Jim

Soft in the Head . Ah , the Television Again . :roll:

Wonder if Heat Treatment would be applicable if the Alloys amenible .

Matt Spencer said:

Soft in the Head . Ah , the Television Again . :roll:

Wonder if Heat Treatment would be applicable if the Alloys amenible .

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The aluminum will harden slightly with time and normal heat cycles. Not enough to fix a seriously overheated head.

To actually re-heat treat it would require removing valve seats and guides and heating to around 900 F. followed by a saline quench [pickle]. Then it could be re-hardened. Then everything would have to be re-machined. I have gone through the process one time and never will again. Jim

comnoz said:

To actually re-heat treat it would require removing valve seats and guides and heating to around 900 F. followed by a saline quench [pickle]. Then it could be re-hardened. Then everything would have to be re-machined. I have gone through the process one time and never will again. Jim

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I bought an 850 head a few days ago and plan to play around on that thing a lot for a 9xx. Big valve conversion incl a revised pushrod and rocker geometry, CNC porting, CNC bathtub combustion chamber etc. - so there will be a lot of welding and remachining involved and I was actually planning to grant it a few relaxing hours in the oven after welding. Could you be a little more elaborate on re-heat-treating the casting? I've been trying to find out a bit more about old RR-materials (and were told by a disgusted old caster that he wouldn't touch these "cocktails from hell" .... :mrgreen: ) but so far failed miserably. I'm a bit surprised that it'd need salt quenching - that would render my DIY approach "slightly less feasible". :wink:


Tim

I have had the experience with an Australian Ford Falcon a few years back, as far as the Commando head is concerned, I think we are all lucky a fella from Perth Western Australia has decided to invest in manufacturing a new head for Commando's, better than original too.

Cheers Richard

stockie2 said:

I think we are all lucky a fella from Perth Western Australia has decided to invest in manufacturing a new head for Commando's,

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I think I've heard of that guy before. 8)

better than original too.

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That's the problem. They are waaay to good to even think about playing around with them.


Tim

I bought an 850 head a few days ago and plan to play around on that thing a lot for a 9xx. Big valve conversion incl a revised pushrod and rocker geometry, CNC porting, CNC bathtub combustion chamber etc. - so there will be a lot of welding and remachining involved and I was actually planning to grant it a few relaxing hours in the oven after welding. Could you be a little more elaborate on re-heat-treating the casting? I've been trying to find out a bit more about old RR-materials (and were told by a disgusted old caster that he wouldn't touch these "cocktails from hell" .... :mrgreen: ) but so far failed miserably. I'm a bit surprised that it'd need salt quenching - that would render my DIY approach "slightly less feasible". :wink:


Tim[/quote]

Tim, I agree with the disgusted old caster.
I don't recall the exact formula I got from a specialist some years ago. What I do recall was just over 900 degrees for 8 hours and air cool to about 800 degrees and then quench in a stirred saline solution. This completes the annealing and redistributes the alloys in the metal in preparation for precipitation hardening. The hardening process was 250 hours in an oven cycling between 100 and 370 degrees.
Any thin sections are likely to crack and oversized seats and rocker spindles will need to be fitted. Everything will be crooked.

The way I do it now is I monitor the casting core temperature with a thermocouple when welding. I try to keep it under 500 degrees which means very short welds and a cooling fan. That limits the annealing to the immediate area of the weld. Follow that with a few days in an oven at 350 and you will generally have a usable piece. The weld will be fairly hard, the area next to the weld will be soft but if the core of the casting is not annealed then the head will hold its shape. Jim

comnoz said:

What I do recall was just over 900 degrees for 8 hours and air cool to about 800 degrees and then quench in a stirred saline solution.

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Thanks a lot for the info, that helps alot already. One questionremains: Saline solution in the sense of a aqueous solution with some salt or molten salt quench furnace? Big difference .... :wink:


Tim

Tintin said:

comnoz said:

What I do recall was just over 900 degrees for 8 hours and air cool to about 800 degrees and then quench in a stirred saline solution.

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Thanks a lot for the info, that helps alot already. One questionremains: Saline solution in the sense of a aqueous solution with some salt or molten salt quench furnace? Big difference .... :wink:


Tim

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Just salt water quench. I don' recall the ratio but they wanted it cooled fast. Jim

comnoz said:

Just salt water quench. I don' recall the ratio but they wanted it cooled fast. Jim

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That sounds better .... :wink:


Tim

Man oh man, what a great site. Good stuff.

Tintin said:

comnoz said:

Just salt water quench. I don' recall the ratio but they wanted it cooled fast. Jim

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That sounds better .... :wink:


Tim

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You just need a little unobtainium. And a few hours. Jim

Jim, what do you have there, do tell. And start a new thread with jewls like this around your shop. I need more!!!!

That is a perk. A new casting with no ports. One of a kind- not for sale. Jim

A fullauto perk? cool.

Were the heads hardened during original manufacture or is that something which occurred naturally as part of the casting process ?

79x100 said:

Were the heads hardened during original manufacture or is that something which occurred naturally as part of the casting process ?

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It is normally started in the casting process. They may be precipitation hardened after casting. I don't know how they were originally done however. Jim

comnoz said:

You just need a little unobtainium. And a few hours. Jim

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I know a source for unobtainium.... 8)


Tim

79x100 said:

Were the heads hardened during original manufacture or is that something which occurred naturally as part of the casting process ?

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The heads are cast from Hiduminium R.R.53 B and this obviously should have gotten the full treatment. That means they are cast in sand moulds, they solidify, then the need solution heat treatment to pretty close to their melting temperature to "correct" the insufficient "quenching", then they are rapidly cooled aka quenched to "freeze" the molecular structure and finally they are heat treated at much lower temperatures temperatures to fine tune their properties. That is the theory ..... :wink:

The quenching can be done in cold or hot water, in cold or hot oil, different gases and molten salt - depending on at which temperature you "want to take the picture" of the microstructure. I have a relatively goo HT oven at hand which could do the solution treatment and the ageing - but when Jim mentioned "saline quench" I initially though that would mean a molten salt bath which is slightly beyond my powers. Just slightly..... :mrgreen:


Tim