Weber IDF Main jet help Options

[tornik550]

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]

I would suggest that for optimizing a carb setup to do it the following way. I learned this the hard (very hard) way when I tried messing with the race car when I went from a 2.2L four to a 2.8L four and then into a 2.2L six.
1. Start at the front, I.E. make sure the tank is clean and rust and junk free.
2. Install a fuel filter at pump suction.
3. Make sure you have the correct fuel pump, those little Facet "cube" shakers are bad for the float settings due to pulses.
4. Make sure fuel lines are large enough, 1/2 inch are great.
5. In the engine compt. do not let the fuel lines touch anything that generates heat and even covering them with fire sleeve is a good idea.
6. Add a pressure gauge just before the carbs so you will know what pressure is acting on the needle and seats.
7. Try to either add an O2 sensor/meter in your exhaust or borrow a meter so the car can be tuned to correct mixture.
8. Make sure to use the insulating spacers under the intake runners to keep heat away from the carbs.
9. Set float heights to the middle to start with and adjust as necessary if needed. Make sure to have the Weber repair books handy and refer to then often.
10. If the jet sizes seem a bit too far out of what normal should be, look for something wrong with the engine setup such as wrong venturi size, weak spark, etc.
11. When starting out, make sure ALL other items are in like new shape such as plugs, points (if used), valve adjustment, etc is not going to have a negative and masking effect on the carb tuning.
12. Do not ever try to sync the carbs by ear, use one of the professional synchrometers and make sure they are sync'd when starting.
13. Run the car ofter, especially in CA where the gas is crap and will let lots of junk settle into the bottom of the carbs.

Hope this helps some.

[ME733]

I would suggest that for optimizing a carb setup to do it the following way. I learned this the hard (very hard) way when I tried messing with the race car when I went from a 2.2L four to a 2.8L four and then into a 2.2L six.
1. Start at the front, I.E. make sure the tank is clean and rust and junk free.
2. Install a fuel filter at pump suction.
3. Make sure you have the correct fuel pump, those little Facet "cube" shakers are bad for the float settings due to pulses.
4. Make sure fuel lines are large enough, 1/2 inch are great.
5. In the engine compt. do not let the fuel lines touch anything that generates heat and even covering them with fire sleeve is a good idea.
6. Add a pressure gauge just before the carbs so you will know what pressure is acting on the needle and seats.
7. Try to either add an O2 sensor/meter in your exhaust or borrow a meter so the car can be tuned to correct mixture.
8. Make sure to use the insulating spacers under the intake runners to keep heat away from the carbs.
9. Set float heights to the middle to start with and adjust as necessary if needed. Make sure to have the Weber repair books handy and refer to then often.
10. If the jet sizes seem a bit too far out of what normal should be, look for something wrong with the engine setup such as wrong venturi size, weak spark, etc.
11. When starting out, make sure ALL other items are in like new shape such as plugs, points (if used), valve adjustment, etc is not going to have a negative and masking effect on the carb tuning.
12. Do not ever try to sync the carbs by ear, use one of the professional synchrometers and make sure they are sync'd when starting.
13. Run the car ofter, especially in CA where the gas is crap and will let lots of junk settle into the bottom of the carbs.

Hope this helps some.

....................I would make the following observation and comment on your recommendations......add( 1A.) always add and install a seperate fuel pump cut off switch....this will allow you to run the engine,and shut off fuel supply, which empties the float boals. Then you can transport the race car without fear of flooding it,causing a hydrolic-lockup,...naturally this assumes you installed the fuel lines in such a manner as to NOT have a syphon effect going on...Your # (3) facet pumps generally are not used on race cars as most racers want a higher level of quality, fuel pump. They are fine for street cars.the pulsation effect is absorbed in the fuel line and pressure regulator. the float needles are bouncing anyway and are not going to be affected by the pump...Your # (4) 1/2/inch fuel lines is just nuts., unless you have a fuel/blown /dragster. that rediculious large size is just a larger heat sink,far more difficult to install in a protected manner,the fuel pumps and regulators do not have that inlet/or outlet size threads.(unless your going to specially made ultra high volume drag racer stuff)...Your #5...covering the fuel lines with "fire sleeve"... will just trap and hold heat against the fuel lines, obscure any ABRASIONS/or cuts that might occur and is a VERY BAD idea...Your #7... an o2 meter is ok, except that for almost the same money an EXHAUST gas temperature guage is far more accurate, and useful. (and it,s what you see in race cars not an o2 guage.)......hope this helps.