My car had a small backfire this morning and I'm pretty sure I blew the power valve. Any idea what size I should replace it with. I have a pretty much stock 305 L69. I've never replaced one before, what is the procedure?

Thanks

 

If you have an automatice, get the car upto operating temp, put it in gear then have a buddy take a vacuum reading and see what you come up with. Off the hip for s tock type motor you'll "generally" be in the 16" of vaccum. A common PV for a stock motor is the 6.5. Basically and in a nutshell the PV rating should be half of what your total vacumm reading is.

Changing it is simple, get a old pop bottle and cut off all but the butt 2" or so, use this as a catch can. Remove 1 of the bottom bowl bolts and allow the fuel to drain into the pop bottle you cut off. Once the fual stops running out, remove the remaining 3 bolts and take the bowl off-careful not to rip the gasket. Once the bowl is off, carefully remove the metering block and the PV will be on the back side of the metering block and take a 1" wrench to remove it. If it's a newer carb, the PV is probably fine since they all come with anti blow out protection, but as cheap as they are it's cheaper to replace it than buy the tool to check it.