Can you adjust a tial blow off and and if so how it doesn't work as well as it did with higher vacume engine only has about 10 hg at idle now

 

You cannot adjust the tial blow off valve, they have preset springs inside the body of the valve. I had a problem with mine opening on my race car, since I have larger cams, and was not getting good vacuum. I ordered the 18in vac spring and it works perfect now. I dont know how low of springs they make. I would call and ask.

Jeff