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Question on Exhaust Header Air Injection

My '89 Ford 460 engine was recently diagnosed with low compression on a couple of cylinders and found to be burned valves. The mechanic who I'm helping, pointed out to me that the air pumps that inject air into the exhaust headers, as part of a pollution control system, were not working as the pulley belt had been removed. To my knowledge, the vehicle has been driven about 12,000 miles without the air pumps working. The question that is raised is, does the injected air into the exhaust headers, which enters at about two inches along the header from the engine block, serve to cool the valves in any way? In other words, would the air pumps not working have caused the burned exhaust valves?

Thanks; Barry

Reply to
B.G.
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"B.G." wrote in news: snipped-for-privacy@uni-berlin.de:

In a word, No. KB

Reply to
Kevin Bottorff

No. Exhaust valves are cooled by the short intermittent contact with the valves and the valve seats. Having the valves too tight can burn them, as the contact needed to cool is not enough. Also, hotter than normal combustion temps can burn valves. IE: constant pinging, EGR not working, etc, etc... All the lack of the air system will do is cause you to flunk the smog tests big time. The air helps burn unburned fuel as it comes out the exhaust. Some systems also need the air supply to the cat converter. You should hook it back up. It doesn't hurt performance, or rob power to any large degree, and your car will be much cleaner burning. If you have to have smog tests, as we do here, lack of the air system will usually cause the car to bomb the test. Too high a hydrocarbon level...Even if the cat can clean it up, it harms the cat by running way too hot. Unhooking smog gear is usually a bad idea. It can hurt you in many ways that many don't consider. IE: Many newer cars are very critical as to the back pressure of the exhaust. Some slap new low backpressure exhaust systems on, and wonder why all of a sudden performance went

*down* instead of up. The new low backpressure confuses the puter, and also some EGR valves are backpressure sensitive. MK
Reply to
Mark Keith

Interesting I have been told that 460 never burn valves. I am not sure why but I would expect there is something that is not right. I.E. like valve springs that have lost there compression thus not setting the valve right. I have a smog pump on a 1983 460 that I have disconnected because all it does is heat up the exhaust manifolds. Yes I need to hook it up when I go to emission tests put then the belt comes back off. If I had a cat convertor I would be leaving it on but don't so can not see any reason other than maybe a little less pollution to leave it on. It is run off of the alt. on this year so added extra wear to the alt. when it is hooked up.

I will be interesting to know why the valves burnt.

Ron in PHX AZ

B.G. wrote:

Reply to
Ron

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