Hey, I've got a 91 Tercel and am doing a head gasket on it. Does anyone know what size and type of tool is used on that head bolt? It uses some sort of triple square or 12 point internal drive but nothing seems to fit. 10 mm 12pt is too big, 8mm spins uselessly and I do not see anyone listing a 9mm. What have you used?

Could you just confirm with me that you've tried a 9mm ?

I can't seem to find anyone making a 9mm to try. I only find even sizes. I called the maker of the headbolts who didn't seem to know either. They called a local Toyota dealer who suposedly said 9mm but it seemed like they were just repeating my guess. Is "triple square" and "XZN" the same thing?

That's very odd. 9mm is available to purchase everywhere up here in Canada. Any tool store.

You could use a vernier or caliper to find the size and do the same at the tooling store to match them.

I don't know anything about tools "triple square" and "XZN".

Well, mystery solved. It uses an 8mm Tercel/Paseo specialty driver. I bought an OTC 6022 for $35. (after waiting 3 weeks on back order). It fit just perfectly and said 8mm but apparently different fron other 8 mm. Runs great now.