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 Post subject: Need some weber help
PostPosted: Tue Oct 29, 2013 8:37 am 
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Joined: Wed May 21, 2008 2:16 pm
Posts: 869
Location: Oklahoma City
Okay, I need some help from the black wizards of weber. I am trying to get my weber 45 DCOE tuned right, before I go all crazy from it. Right now, specs are as follows. Stock 20R with 118K or so, long tube 4 to 1 header, single 45 DCOE; venturis(chokes) 34; Main Jets 145; Air Corrector 150; Emulsion Tube F16; Idle Jets F855. Problems are; Horrible fuel econ, I know I will not get incredible MPGs, but I should get better than 8MPG. Bogging off idle, power dies about 3000-3500 rpm. Running terribly rich, idle mixture screws are all the way in. My thoughts are bigger chokes, more like 38 rather than the 34s that are in there. Bigger mains 150 or so. Way bigger air correctors 200 to 205 and smaller idle jets. Does any of this sound right to anyone? I have been doing a ton of research and everything tells me that the carb is set up completely wrong for the car Any help, advice or insight would be appreciated. Eventually, I will be switching to an R1 setup, but I would really like to get the weber running right so I can eventually sell it when the R1s are ready to go.

1976 RA29 project car, now a driver!!!!!
1985 MX72 soon to be...

 Post subject: Re: Need some weber help
PostPosted: Thu Oct 31, 2013 1:14 pm 
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Joined: Thu Apr 15, 2010 3:00 pm
Posts: 51
Location: St. Augrida, FL
I think your thinking is about right, this is tuning data i found for mikuni dcoe carbs, but the jet sizes and progression should be fundamentally similar. http://www.mikunipower.com/PHH01.htm scroll down to the Mikuni PHH Carburetor Service and Tuning Manual. Page 19-20. The pilot jets are the ones that effect the first 20% of throttle opening. I think that is where your bogging is. Unfortunately i lost my notes on this. This is a recommended jetting chart again for mikuni applications like 20r http://www.mikunipower.com/PHHCarbs/PHHcatalog29.jpg . Hope this helps.

 Post subject: Re: Need some weber help
PostPosted: Fri Nov 01, 2013 11:55 pm 

Joined: Wed May 26, 2010 7:38 pm
Posts: 80
Location: St. Marys Ga
Before you go changing jets what is the history on this carb. Has it been sitting on a self, was it on any other car, if so what engine size. Running rich on a dcoe can be from leaking floats floats, incorrect float level adjustments. Bogging off idle can be caused by blocked progression holes. bogging at 3000 can also because float adjustments or a stuck needle valve. If the carb has not been rebuilt in some time I recommend that you do this first. I can get you a copy of rebuild instructions if you need them.

For tuning jets this is a good start:http://www.racetep.com/webjettune.html

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