I am trying to replace my oil pump, and cant get the exhaust off to clear the pan coming down. the bolts are rusted on pretty good, but my problem is a 1/2 is too small, yet a 9/16 is too big. there is nothing in between! i also tried a 13, 14 mm sockets and neither of them worked. so my question is, how can i get these bolts out??????

 

heat, lube cutoff wheel.. you may have to remove your manifolds to replace the studs if they break off..
Its a crappy job. good luck

 

Lots of heat, cherry red hot!

 

13mm is between 1/2" and 9/16". Remember, these GM cars contain alot of metric fasteners. More likely though, the nuts are deteriorated from years of rust and heat. There is a tool that I use in situations like this, often called a turbo socket. You drive the socket onto the worn nut with a hammer. The teeth of the turbo socket will bite into the nut and grip it where a normal socket will slip off. And of course, lots of penetrating oil and maybe a torch.

 

cut them off and install new ones.

 

I've spent more time than I wish to think about drilling out broken exhaust manifold flange studs. Chevys are famous for broken manfold bolts. Believe me. It's easier to remove the nut or even the stud. Even if you have to heat it red hot repeatedly to roll it a quarter turn each time and even if it takes hours. Than it is to drill out and rethread them.

 

I just did mine last night on my 3.1L.... I heated them to cherry (careful not to go past just getting red).. Then, I used a small air impact wrench to get them off... Before taking any cutting tools to them, get a stripped nut remover socket... Harbor Freight sells a set... They look like a socket except they have reverse gripper teeth inside that bite deeper the more you torgue the socket to remove the nut...

 

cool, thanks guys... i didnt have space to heat, as i am doing it with the motor still in the vehicle... (a MAJOR pain in the ***, not highly recommended at all) so i just went ahead and took a sawzall to the bottom of the y pipe that was blocking the oil pan. still never got the pan all the way out, but it dropped down far enough to get the pump replaced. now just gotta figure out how to get the motor mounts lined up again... the motor shifted when i jacked it up... such a royal pain this car is...

 

A pry bar in the right spot will help the alignment process. I can usually get one between the upper and lower mount and shoe horn them together.

 

@ ase doc, that worked, thank you very much