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Posted by chriscase on Monday, September 29, 2008 at 18:45:30 :
In Reply to: Re: Overheated, now backfires going down hill posted by Robert N on Monday, September 29, 2008 at 18:02:51 :
Gas actually ingnites only over a pretty narrow range of of air/fuel. Otherwise wouldn't need chokes.
So a pcv valve that is stuck open will leak the most under deceleration, when the least mix is getting in-took. I just put a 2bbl on my 230, and had stalling and backfiring until I changed from a /6 pcv to a 318 to match the carb.
Then there is also "fuel puddling" where, on deceleration, the mix stays in the intake too long, and condenses the gas into liquid. Which does not burn, gets pumped into the exhaust, heated and vaporized there, and ignites from the heat.
Gas does not always ignite when you think it would.
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