glassbowtie77
Well-known member
I was driving along today steadily at 65 mph, when I let off the gas coming to a red light I noticed a pop pop pop noise coming out of my left sidepipe. Anyone know what causes this?
Your popping is typically a symptom of a lean condition. When running lean, you get a lean misfire when you let off the gas, and unburned fuel enters the exhaust. Richen up the carb.
You'll start getting popping in the exhaust in the mid-15 range if you slam the throttle closed and the rear wheels are pulling the engine over.
DPFI does not respond the way a carb does to having the throttles slammed closed - no comparison. The IAC does not immediately seat upon throttle closure to create the sudden closure possible with a carb, giving the DPFI time to enrichen and correct the induced lean condition without popping. California-emission carbs had a dashpot on the throttle lever to prevent the sudden closure, and this would reduce the tendency to get the lean misfire popping: emissions are very high when the lean misfire popping occurs.
You won't get exhaust popping in the high 13's - that mixture will produce a very smooth and well-sounding deceleration idle. One of the problems we're seeing is that most fuel around the country now has ethanol additives (about 15%), and this causes a lean condition. If you have 15% ethanol, you cannot run mixtures any leaner than about 14.2:1 without getting popping. If I know a carb is going to be used with ethanol additive fuel, I usually set it up in the high 13 range to assure no popping.
Your popping is typically a symptom of a lean condition. When running lean, you get a lean misfire when you let off the gas, and unburned fuel enters the exhaust. Richen up the carb.
The popping noise is still there. Upon further inspection the header gasket is blown out by cylinder #1 from the bolts coming loose. I am ordering a set of Stage 8 locking header bolts from Summit along with a new set of header gaskets. Any suggestions as to which are the best gaskets to buy? I am looking at a set of soft aluminum gaskets from Percy Performance. They are supposed to seal the best and they claim they are burn out and blow out proof. I am also looking at a set of Mr. Gasket Copperseal gaskets, any opinions on these or is there something else that I should be looking at?