View Full Version : What are these screws on the carb

09-16-2004, 06:03 PM
I have a 70 gt6 with stromberg 150cd carbs. I found that i have a model with adjustable needles or are spring loaded. But I have read the haynes manual and still lost.

I no what the idle screw is. But on the other side I have two other screws.
The bypass screw and the idle mix screw.

What do they do and were should I set them to start. Do I also need to adjust the needle and if I pull it up what does it do compared to going futher down.

Lost Sorry for any of you who is going to try and explain this. Thanks for the help. Tom

09-17-2004, 12:29 AM

Rick O.
09-17-2004, 11:46 AM
If the 150's are similar to the 175's, the idle screw is on the left side of the carb and mates with a lever attached to the throttle shaft. For an initial adjustment (with the folded linkage couplings loose), just turn that screw until is contacts the lever, then one more turn. When done, tighten the folded couplings.

An initial setting for the adjustable needles is 2 turns CCW from full rich. Full rich is obtained by turning the needle CW until the needle bottoms-out (can't turn anymore).

Good luck.

09-17-2004, 12:10 PM
Hey Tom, a Bentley Manual would be of great help in your repair efforts. The Bentley for your specific GT6 model has highly detailed schematic drawings and suggestions for tuning your Stroms.

Get one, you'll be glad you did.

09-17-2004, 06:56 PM
My factory book says that no difference in running will be noted by ear whether the idle trim screws are all the way in, or all the way out. They are to set the exhaust CO content by using a gas analyzer. Go figure.