Weber IDF Main jet help |
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Weber IDF Main jet help |
tornik550 |
Aug 11 2010, 07:29 PM
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#1
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Senior Member Group: Members Posts: 1,248 Joined: 29-January 07 From: Ohio Member No.: 7,486 Region Association: None |
I am in the process of tuning my car after a rebuild. I have dual weber 40's. My engine is a 2.27L. Everything is going pretty well. I am slowly getting the jetting closer and closer. I was driving around at about 60mph yesterday. The head were hotter than I like (325 degrees). I checked the spark plugs and they were bone white. The main jets were at 160. I increased them to 170 (above 160 I only have increments of 10). With the increase to 170, the car is running very well and the temp at around 60mph cruising is around 275. I sped home, tuned off the car and took out the plugs- bone white. I was quite surprised.
The main jet size sounds high too me. Does it sound high to everyone else? Is it possible that I am needing a high main jet size because of the float level? I have my floats set at 10.5 with the gasket. Any opinions would be greatly appreciated |
john rogers |
Aug 12 2010, 11:08 AM
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#2
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Senior Member Group: Members Posts: 1,525 Joined: 4-March 03 From: Chula Vista CA Member No.: 391 |
The rule of thumb I learned when racing which should also apply to street use is that with Webers set the starting fuel pressure at 4# and if you need to make a quick change at the track then changing pressure by 0.5# is the same as changing jet size by a full step I.E. drop pressure to 3.5# and it is like going from 160 to 150 in jet size. The BMW racers also used this and the folks at the Weber repair shop in Gilroy CA agreed. With your pump at that pressure you might be running out of fuel so I would suggest doing a capacity check to see what the flow rate is and why pressure can not get any higher and then solve the jet issues. Also as I mentioned earlier I would really think about installing an O2 sensor to watch things. Good luck with this.
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