I need to know large and diameter about screw to make adjustable pressure regulator on my TB.

I out seal weld or lock.

Regards

 

This may help

Tech Article

 

I saw it, but my question is which exactly screw need to install or replace.

regards

 

i beleive it was a 1/4 20, is what i remember reading somewhere but, don't quote me on it....

 

I'm not sure I understand your question, but I think you're wondering about which screw needs to be modified to make it "adjustable". The tech article Shifty posted above is very accurate, but you probably won't understand everything until you take the fuel pressure regulator off your TBI and see for youself, then it will be obvious.

I just finished converting my stock fuel pressure regulator into an adjustable one. To remove the stud from the spring cup, I had to grind the end out with a dremel becasue it was welded or brazed to the cup at the factory. Instead of putting a slot in the screw, I made a new screw out of aluminum. The threads that screw into the spring platform are M6 x .75. This is a fine pitch M6 thread. At the opposite end of the screw (the end the tech article says to grind a slot) I drilled and tapped a M4 x .7 blind hole, which I screwed and loctited in a M4 x .7 socket head cap screw about 1 inch long. The cap screw to sticks out the bottom of the TBI (just above the MAP vacuum port), allowing me to adjust the regulator pressure on the fly without removing anything. Works great.

For simplicity, just follow the tech article. The only drawback is that once you've reinstalled the FPR, you'll have to take a few things back apart to make an adjustment to the fuel pressure later. Only takes a few minutes, so no big deal.