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3 restos WIP = psycho
 
kenikh's Avatar
 
Join Date: Feb 2005
Location: North of Exit 17
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A question about engine noises (on road trip now)...

Just picked up my new 911 this weekend and am driving it back to Seattle on Monday. I love the car, but as I don't know it very well, have some questions. I am getting a slight 'pop' occasionally in the exhaust note and can hear a slight 'chuff' or puffing sounds from the right side bank of carbs (no MFI yet). There is a subsequent tiny drop in revs when it happens. It is intermittent so I can't figure it out. The exhaust pop doesn't happen at idle, but the carb noise and rev drop does. My guess is slighty leaky gasket in the carb, but my diesel mechanic cousin said it reminds him of a sticky valve. I wasn't worried until his 'expert' opinion mentioned the valve train. The car runs cool and happy, has fresh oil and passed its PPI with flying colors (125 psi and <8% leak at all 6). Any thoughts?
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Old 04-30-2005, 09:48 PM
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A bent valve will have this symptom, but before you worry, and overly lean carb will do this as well. Does it mainly happen at idle?
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Old 05-01-2005, 04:22 PM
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Sounds like the carbs need a good cleaning and balance. The pop is likely from unburned fuel in some cylinders. Its running rich and the heat of the exhaust will cause it to ignite. Note: an exhaust leak will also cause this. the 'chuff' is a lean pop through the carb stack. It is usually muffled by the butterflies at idle.

best of luck with the new car and its road trip home. Sounds like fun. I can't wait to see pics of the car and trip.
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Old 05-02-2005, 06:31 AM
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3 restos WIP = psycho
 
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I think they are a tad lean (which was my original assessment). The PO said it started after the least time he had the carbs adjusted. Thanks to all!
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- 1965 911
- 1969 911S
- 1980 911SC Targa
- 1979 930
Old 05-03-2005, 06:23 PM
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