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Fleabit peanut monkey
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911SC ehaust leak
81SC Slight putt putt backfire at idle. Found an exhaust leak where the drivers side exchanger flange meets the new Fabspeed cat bypass pipe. All other flange connections ok as well as heat exchanger to head connections.
It leaks pressurized air (hose duct taped into tailpipe - 20 psi) from two of the three sides but not at the bolts. I used the new Fabspeed copper gaskets but have a new original type gasket bought from PP. Questions: Can the heat exchanger be warped at the flange? If so - am I buying another? Disassembled the entire system and replaced all gaskets and hardware last year. Is there an order of assembly that I did not follow that could cause the parts to be out of alignment? Are copper gaskets less flexible than the factory type? Meaning, can the asbestos type material fill in the imperfections? The original gasket is really tough stuff. I am doubting this. Can I double up on gaskets? Thanks for your insight. Bob |
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03-16-2010, 04:19 PM
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grateful user
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I had probs. with the copper leaking with my thin flange ssi, swapped to the 74 down gasket, and no probs. since. They do seal better i think.
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fully disassembled, blasted, customized and restored 75 targa with factory hard top, 993 style turbo ft fenders, steel flares, C2 bumpers and rockers, 82 3.0 sc 9.5/1 engine with PMS flywheel, 964 cams, flowed heads, ssi's short geared 915 w/lsd, polybronze, bilstein,working lambda, modified and highly tuned cis, tensioners, pop valve, backdated exhaust and heater, 2300 lbs. no bolt left untouched. 1970 911E. Nice car but needs a re-do. |
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03-16-2010, 04:38 PM
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Registered
Join Date: Oct 2003
Location: Michigan
Posts: 14,093
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I used a thin layer of muffler cement when I put mine back together. I used the asbestos gaskets as I have always had bad luck with copper/metal gaskets on any exhaust I've had.
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1981 911SC ROW SOLD - JULY 2015 Pacific Blue Wayne |
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03-16-2010, 04:45 PM
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Fleabit peanut monkey
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Thank you! Just used the original type gasket and some muffler "repair" goop that was in my tool box. No leaks. Found popping was related to over rich CO.
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03-19-2010, 12:29 PM
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Fleabit peanut monkey
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Follow-up note. Popping was not related to CO adjustment OR exhaust leaks. CO adjustment just changed the symptoms of the problem. Used starting fluid to find two air leaks. One was an injector that had pulled out of the intake runner and the other was the number 4 intake runner with only one nut tightened down.
The loose injector caused the engine to bog down with the starting fluid and the intake runner leak caused the engine to increase rpm. The intake runner leak cured the popping problem instantly. I was never convinced the starting fluid/carb cleaner test worked, but now I am sold - perhaps because I had never found a leak till now. Funny how that changes your perspective. I took maybe 5/8 of turn to lean to dial in the CO to the 45 degree range with the dwell meter test. |
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05-02-2010, 11:59 AM
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1981 Porsche 911 SC Targa
75 Porsche 911
bike
1970 porsche E
