Exhaust port reduction

[Lee]

Something for the chemists?
I have a little issue with the size of the exhaust ports on my aluminium cylinder heads - they are too big.
I know I can reduce them by filling with weld, but is there an epoxy type product out there anywhere which will stand the heat?
I would have thought there must be some super new product from the aerospace industry somewhere which could be used for this purpose?
I have heard of products which are OK for inlet ports (Devcon etc) but won't stand the heat in the exhaust port.
Out of interest how hot do exhaust ports get? But I digress - Is there a product suitable for filling exhaust ports? If not, is there a specific technique which needs to be used for filling with weld?
And if I need to go the welding route is there anyone out there - in the UK who can do this for me?

 

[Peter Delaney]

Hi Lee, Judging from the dull red glow we got out of the headers on the dyno at less than 3000rpm under prolonged load, I would be surprised if anything other than metal would be able to withstand the heat. I have seen videos of headers at full load & high revs - the dull red glow becomes just a tad bright !

My simple understanding is that smaller ports/pipes can yield higher torque at lower revs, but larger ports/pipes yield higher hp at higher revs. (A huge generalisation, I know, but one derived from listening to a lot of people who have been there !).

Unless you are trying to get the last ounce of performance out of the car for racing, the port size probably doesn't matter much in a 1000kg car on the road with the sort of power available.

Kind Regards,

Peter D.

 

[StuartB]

Hi Lee,
Try http://www.kap.uk.com/engineering.htm they may be able to help you out. Usual cavets apply /ubbthreads/images/graemlins/grin.gif

 

Try Belzona. Very good stuff, should also be very expensive. Used to rebuild all kinds of stuff. Their website is www.belzona.com

 

[Gary Gibbs]

You could probably buy new heads for the price it will cost getting someone to redo the ports.

 

[Lee]

Thanks for the leads. Can anyone tell me how hot the port is likely to get around the manifold joint? Would it reach 2000F (1093C)? 1000F (540C)? I've found a couple of products which may be suitable.
Thanks

 

[James]

Lee,

I imagine that the heat will just rip out anything you put in, and I imagine you will find it nigh impossible to match what you do from port to port. If you can I would go for a new head, shop around before going for the extreme measure! Good luck. /ubbthreads/images/graemlins/smile.gif

 

[Ron Earp]

I think typical exhaust port temps are 1400-1600F. Not abolsutely sure, but I think this is in the region.

Don't put anything but metal in there. In fact, I'd follow the eariler advice - either get larger headers or different heads. You'll be better off.

R

 

[Gary Gibbs]

I think EGT's on a properly tuned gasoline engine run ~~1300 F.

 

[Kevin M]

You would have to match it with a similar aluminum alloy. If you use anything with different thermal expansion characteristics it will tear itself apart the first time it heat cycles.

Kevin