I just spent about 3 hours drilling a bolt I had stuck in the block from when I broke it with the waterpump. I finally got it all drilled out and need to re-thread it. Its the one in the middle on the passenger side of the car. Whats the next size thread to go with?

 

Water pump bolts are 3/8-16. If you are going to use a thread insert repair, you will need to drill it out to the size specified for the insert.

 

Excuse my ignorance shoe box, but would the next tread size be? Im not familiar with the standard system measurements, only metric.

 

You can't just go to the next size, it'll be too 'fat'..
You need a HeliCoil insert[that's what shoebox refers to] which consists of the insert, the SPECIAL tap for that particular insert size, and an install tool..
The tap is matched to the 'insert's' outer threads..
The hole size needs to correspond to the tap size..
Then you tap it with the special tap, then insert the threaded insert[ looks like a spring]
This allows you to use the appropriate standard bolt again, and is as strong as the original threads[ possibly even stronger, it definitely is stronger when used in aluminum..]