Re: straight pipe burns valves??????

Posted by Mike (MI) on July 02, 2003 at 05:21:58 from (207.16.136.22):

In Reply to: straight pipe burns valves?????? posted by rustywallace2 on July 01, 2003 at 11:58:37:

I have to jump in here once more regarding "warped" valves because of cold air getting to them. That is also a "wive's tale". Consider what happens when it's 0 degrees out, and you fire the engine up. The exhaust valves goes from being almost 0 degrees, to a few hundred degrees in just a few seconds. That doesn't warp it. After the engine has been run and is warm, there's no way you could get cold air to the valve anyway. I supposed it's possible that the engine could stop in the narrow window where the intake and exhaust valves are both slightly open, somehow allowing air to flow back through the carburator - but very unlikely. After the engine is warmed up, there's enough hot mass there to heat up any air that might somehow make it near the valve. Also, think of this condition in current fuel injected automotive engines: The fuel injector sprays fuel on the back of the intake valve because its hot and will vaporize fuel quickly. There's combustion tempratures on one side of the valve, and cold fuel being sprayed on the other side. Trust me - cold air isn't going to warp the exhaust valve. I work in a R&D engine dynamometer lab for Eaton Corp, who produces 80% of the poppet valves used world wide - we have never had a valve fail due to cold air. I will say, however, that it is hard on exhaust valves to go to full speed and load as soon as a cold engine fires up. The valve has to go from ambient temp. to around 1500 degrees F in just a few seconds. The thermal stess created will actually make the valve crack over many of these thermal cycles. Hope I haven't offended anyone. I'm just hoping everyone will dismiss the "warped valve" story as myth. I'll get off my soap box now.

Follow Ups:

• Re: Re: straight pipe burns valves?????? Terry 08:55:49 07/03/03 (0)
• Re: Re: straight pipe burns valves?????? Steve - IN 09:31:13 07/02/03 (3)
  • Re: Re: Re: straight pipe burns valves?????? Mike (MI) 10:47:08 07/02/03 (1)
    • Re: Re: Re: Re: straight pipe burns valves?????? Steve - IN 11:04:34 07/02/03 (0)
  • Re: Re: Re: straight pipe burns valves?????? Dr.EVIL 10:26:04 07/02/03 (0)

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