How much does it cost to make sure head isn't warped?

 

Prices range from free if you remove the head and take it to someone. It's an easy check once off the vehicle. You can check yourself if you have a straight piece of glass or steel. Close enough to know at least.

Or $200-300 to have someone pull the head and check it. Getting it back together will cost a similar amount on the higher side of that estimate, plus whatever else needs to be done.

Don't quote me.

 

If pulling the head, just take it to the machine shop and let them send it over for a quick shave. If it has been even once overheated, it will have some slight warpage and the straight 6 heads are known because of their length. If I pull a head, regardless of miles, I make sure its straight by dropping it off for someone to run through for a new shaved, straight mating surface.