Weber help needed!
10-15-2002, 01:10 AM
#1
Three Wheelin'
Thread Starter
Weber help needed!
Recently picked up a 69 912 with a 2.4L (bored 2.0L) 914 flat-4 under the rear lid. It's equipped with dual Weber carbs and I haven't the faintest idea how to tune these things.
The car had been running fairly well until an "expert" fiddled with them and now the car is a real dog. It sounds like it's running on 2 cylinders when idling and pops and backfires while cruising at part throttle. At full throttle, it gets along rather well but anything up to that point is just a symphony of pops, farts and raspberries. Any suggestions on the steps I need to take to get these carbs running in sync and in tune again? Be as detailed as you need to be as, being an aircraft mechanic by trade, I'm somewhat mechanically inclined and not easily scared by technical jargon. I just have no experience with Weber carbs.
The car had been running fairly well until an "expert" fiddled with them and now the car is a real dog. It sounds like it's running on 2 cylinders when idling and pops and backfires while cruising at part throttle. At full throttle, it gets along rather well but anything up to that point is just a symphony of pops, farts and raspberries. Any suggestions on the steps I need to take to get these carbs running in sync and in tune again? Be as detailed as you need to be as, being an aircraft mechanic by trade, I'm somewhat mechanically inclined and not easily scared by technical jargon. I just have no experience with Weber carbs.
10-24-2002, 08:58 AM
#2
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I suggest that you get in touch with PMO in Santa Monica (310) 393-5423, they are a leading authority on Webers and make their own version of the 40, 46 and 50 triples. They will have all the spares you will ever need available and also have a useful little set up guide that they sell with new carbs, I'm sure they will fax you one if you ask nicely.
10-25-2002, 09:52 PM
#3
Although you have Weber 2 barrel carbs, the operating principal of all Webers is about the same. Here's a general overview.
Make sure all circuits are operational, i.e. not blocked. This means partially disassembling them if necessary and probe each circuit with air or carb cleaner spray. Jet sizes are usually marked (don't necessarily assume they weren't drilled though). Get the proper tool to check float level. Older carbs may have some wear at the throttle shaft bore which will upset any attempts to adjust the idle. Check for excessive play in this area.
After you know the carbs are clean and healthy with the correct jets, make sure the carbs are setup the same, then make equal idle adjustments on both sides. Use a tool to measure side-to-side carb balance (Syncrometer or Unisyn). A CO meter will help determine proper idle mixture.
I also suggest getting one of several books on the subject (I like Pat Braden's book) for background info. There's probably tons of material in the archives as well.
Regards,
Sherwood Lee
<a href="http://members.rennlist.org/911pcars" target="_blank">http://members.rennlist.org/911pcars</a>
Make sure all circuits are operational, i.e. not blocked. This means partially disassembling them if necessary and probe each circuit with air or carb cleaner spray. Jet sizes are usually marked (don't necessarily assume they weren't drilled though). Get the proper tool to check float level. Older carbs may have some wear at the throttle shaft bore which will upset any attempts to adjust the idle. Check for excessive play in this area.
After you know the carbs are clean and healthy with the correct jets, make sure the carbs are setup the same, then make equal idle adjustments on both sides. Use a tool to measure side-to-side carb balance (Syncrometer or Unisyn). A CO meter will help determine proper idle mixture.
I also suggest getting one of several books on the subject (I like Pat Braden's book) for background info. There's probably tons of material in the archives as well.
Regards,
Sherwood Lee
<a href="http://members.rennlist.org/911pcars" target="_blank">http://members.rennlist.org/911pcars</a>
10-29-2002, 11:12 PM
#5
PMO recommends setting the fuel level between the upper two lines.
Hope this helps,
Sherwood Lee
<a href="http://members.rennlist.org/911cars" target="_blank">http://members.rennlist.org/911cars</a>
Hope this helps,
Sherwood Lee
<a href="http://members.rennlist.org/911cars" target="_blank">http://members.rennlist.org/911cars</a>
