Header clamp gap

V

Vince

Hero member
I seem to remember for the finned header clamps to work at there best they need a small gap from the head,other than not bottoming the fixing nuts what's the reason behind this heat wise?
 
Hi Vince if you haven't got a gap between the head and the clamps you may not get the header to seal against the gasket in the port.
Quite often the thickness of that copper ring gasket determines the gap between the clamp and the head!!
 
I thought I had read Phil Tod saying having the finned clamp hard up against the head had a bad effect on removing heat away from the port. At the time I would have thought the opposite, yes I get the seal pressure bit.
It's the heat extraction comment, not good for no gap bit I was wanting a clarification on. I would have though having all that finned surface area in contact with the head would be a good thing heat removal wise.
 
I suppose you could argue that the greater solid mass (if the header clamps touched the head) might retain heat longer, whereas with an air gap there is more opportunity for air flowing past and around to wick away more heat.
I suppose the question is what is the primary purpose of the header clamp, to remove heat directly from the head or from the downpipe? (as well as fc the downpipe to the head natch)
 
Apart from sealing issues, I'd guess the reason for the gap is to keep the heat of the exhaust gas away from the head as best as possible, going mainly into the exhaust tube. If the gap between clamps and head is closed up, there will be a short circuit for the heat going via the contact surface of the clamp into the head. With a gap maintained, heat from the clamp will be only transfered via the stud bolts, which is way less than the amount of heat that would be transfered by a clamp being in full contact to the head. The fins on the clamp are probaly there to provide some cooling to the clamp itself.



 
mauricejota7604 said:
Hi Vince if you haven't got a gap between the head and the clamps you may not get the header to seal against the gasket in the port.
Quite often the thickness of that copper ring gasket determines the gap between the clamp and the head!!
Click to expand...
Well they did when it left here last or have you been playing with your bike again Vince hmmmm ??

Interesting take on what the header clamps are for and here was me thinking that they were to hold the headers in place and to provide an airtight seal and the reason for the fins was one of simple aesthetics...........cant see them doing much in the way of cooling those ultra hot exhaust gasses though...........otherwise they would use finned one in hi output racing engines I would have thought.

 
No a discussion on another site re the advantages of Ceramic coating with heat dissipation being one of these. I thought I would add the bit I remember about how the gap helping with this,I was surprised when I read it the first time. I would have though having the clamp with all those fins touching the head aid cooling,but I seem to remember the gap between the finned clamp and head  was better but not why. And typically when I write something I usually get challenged  for talking BS, like I am defying some set in concrete fact written by GOD.I am always happy to learn something new,and wanted some info re this.
Its also good to stir up some interesting debate here,it's been getting too quiet lately,we need some more input re posting stuff.
 
Vince no worries ...........say I can attest to the Ceramic coating keeping the heat in the exhaust ........ it does make the outside of the pipes cool............never burnt myself on your pipes love em they are great.

If it on another site then tell em something like this.

" that you have spent many years researching this exact same question and your conclusion gleened over years of researching and also  from trial and error has concluded the ideal gap is in fact an even 20 thou all round, not 15 and certainly not as much as 25 thou between their finned clamps and the head and that the gaskets should be a mixture of copper and ceramic fiber based material, which when torqued correctly will provide a perfect seal however this must be used in conjunction with ceramic coated haeders and zinc plated exhaust clamps at the header ... this will achieve a drop of 5.7 degrees C when using hi octane fuel and running the engine at a steady 4200 RPM over a period of 42 minutes... :-X

That will get them thinking... stay safe and hope you are well over your illness now.. so we will see you at next weeks club meeting ?

And in case anyone asks why 42 minutes well according to Authur Dent and Ford Prefect the answer is 42.
 
Sounds like great info, BTW that would go down well on that site,they had a thread about Towel Day last week. Seems its a world wide day to remember how important a towel is to Hitchhikers. Well over whatever I had wrong, got a rear tyre coming for The Snowy Run. I wanted one of those T30 Bridgestone Radials in 140,they're new but not imported ti OZ. I talked the importer into bringing that size in but they won't arrive till March,
so It another sports demon till then.


 
G'day Vince. If it makes it any easier to follow Gravelroad's argument - the exhaust clamps run hotter than the head, because they're in direct contact with the exhaust header. If they are in contact with the head they'll conduct heat back into the head.

I think we're only talking about a marginal effect. I don't reckon it would be a catastrophe if they were in contact with the head. But every little bit of cooling helps.

Ceramic coating doesn't aid heat dissipation, it acts as an insulator keeping the exhaust gases hotter. Like the header pipe wrapping favoured by hipsters. I suppose in an ideal world the clamps should be made out of something non-conductive. Problem is that most non-conductive materials aren't structurally suitable for such applications.
 
They don't do a 140 in the active. The T30 Bridgestone is now called a T30 Evo ,supposed to be stickier than the T30.
 
and there was me thinking we need to wrap our sorts so up in cotton tapes to keep heat IN😅Maybe that only applies if you wear a lumberjack shirt and sport a need Kelly beard?
 
I think the primary purpose of the header clamps is to keep the headers from falling off...  :D

I reckon the finning is purely cosmetic.  Lots of air-cooled engines with plain fixing rings/clamps.

piet
 
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