dees

any one had this porblem i just put a bbk throttle body 52mm on my 1986 corvette 350 tpi made all the adjausmens car start just fine but with engine runing the thorttle is real hard push. with engine not runing it/s fine

bjankuski

Is the throttle body new? Sounds like the throttle body shaft is sticking to the bearing surfaces when you have high engine vacuum. That is usually a sign of a worn throttle body housing where the throttle body shaft slides threw housing. Spray some WD-40 on the throttle body shaft were it goes threw the throttle body and see if the problem gets better. If it does you have found your issue.

2LZ

I just installed a BBK 52mm on my '96. Yes, the spring is very stiff making it a harder pedal than stock. Apparently, they don't want the throttle to stick open like my Pro Products TB did.
If it gets lighter with use, cool. If not, my foot will adjust.

383vett

If the throttlebody bolts are tightened unevenly or overtightened, some binding can occur and you will have the porblm.

cv67

ahh I see what you did there