carburetor guru's????
06-25-2003 | 10:52 AM
#1
Thread Starter
Instructor
Joined: Jun 2003
Posts: 164
Likes: 0
From: Ottawa, Canada
carburetor guru's????
I have a 72 911E motor with 40mm webbers.
the motor is fresh (<20000km's) and the webbers are as tuned as they can be
The PO left the stock air cleaners on the car as he used it in all weather conditions, where I only use this car on sunny dry days.
I have a constant backfiring issue under deceleration and was wondering if anyone had any suggestions? It's quite embarrasing and is beating the crap out of my exhaust.
I'm using 94 octane fuel. I was contimplating an open elemenet air cleaner to lean the car out a bit but wonder if this will effect the jetting of the carbs too drastically.
I'm new to this whole carb thing, so please excuse my ignorance.
thanks in advance if you can help.
the motor is fresh (<20000km's) and the webbers are as tuned as they can be
The PO left the stock air cleaners on the car as he used it in all weather conditions, where I only use this car on sunny dry days.
I have a constant backfiring issue under deceleration and was wondering if anyone had any suggestions? It's quite embarrasing and is beating the crap out of my exhaust.
I'm using 94 octane fuel. I was contimplating an open elemenet air cleaner to lean the car out a bit but wonder if this will effect the jetting of the carbs too drastically.
I'm new to this whole carb thing, so please excuse my ignorance.
thanks in advance if you can help.
06-25-2003 | 01:57 PM
#2
RL Technical Advisor
Joined: May 2001
Posts: 11,871
Likes: 65
From: Portland Oregon
Hi David:
Well sir, installing open aircleaners will affect the jetting so proceed accordingly.
Backfiring on deacceleration can be caused by several things:
1) Mixture too rich
2) Mixture too lean
3) Late ignition timing
4) Heat exchanger and/or muffler leaks
The first two on the list are big variables due to how the carbs are jetted and how well they have been setup; fuel pressure, float level, etc.
Its easy to check the timing with a light and ensure that the advance mechanism in the distributor is functioning correctly.
Any exhaust leaks or pin holes in the muffler will cause the backfiring.
Hope this helps,
Well sir, installing open aircleaners will affect the jetting so proceed accordingly.
Backfiring on deacceleration can be caused by several things:
1) Mixture too rich
2) Mixture too lean
3) Late ignition timing
4) Heat exchanger and/or muffler leaks
The first two on the list are big variables due to how the carbs are jetted and how well they have been setup; fuel pressure, float level, etc.
Its easy to check the timing with a light and ensure that the advance mechanism in the distributor is functioning correctly.
Any exhaust leaks or pin holes in the muffler will cause the backfiring.
Hope this helps,
06-26-2003 | 01:55 PM
#3
Thread Starter
Instructor
Joined: Jun 2003
Posts: 164
Likes: 0
From: Ottawa, Canada
lol...
I noticed the 2 copper gaskets were non existant on the heat exchanger to the muffler, so I replaced them.
I even went as far as to die grind the surfaces clean and smooth before mating the gasket back in.
Backfire gone......
but
now my exhaust leak is more annoying than when there was no gasket left in there at all
Now.... anyone have any suggestions as to what to use with/instead of the copper gaskets? They have been torqued down properly and still leak.
hmpf.
That's the life of a Porsche owner
I noticed the 2 copper gaskets were non existant on the heat exchanger to the muffler, so I replaced them.
I even went as far as to die grind the surfaces clean and smooth before mating the gasket back in.
Backfire gone......
but
now my exhaust leak is more annoying than when there was no gasket left in there at all
Now.... anyone have any suggestions as to what to use with/instead of the copper gaskets? They have been torqued down properly and still leak.
hmpf.
That's the life of a Porsche owner
06-26-2003 | 03:00 PM
#5
RL Technical Advisor
Joined: May 2001
Posts: 11,871
Likes: 65
From: Portland Oregon
Hi David:
LOL,...You are most welcome, Sir.
Those factory copper sandwich gaskets are pretty darned good IF,.................If the flanges are not warped from being overtightened. I would true the flanges with a flat file and make sure that they are indeed,...............flat.
Nothing better in the gasket dept.
LOL,...You are most welcome, Sir.
Those factory copper sandwich gaskets are pretty darned good IF,.................If the flanges are not warped from being overtightened. I would true the flanges with a flat file and make sure that they are indeed,...............flat.
Nothing better in the gasket dept.
