Cylinder head bolts

This probably a newbie question, but I didn't want to proceed unless I am sure.

I was trying to remove the cylinder head on my P5 today. When I get to the cylinder head bolts, I found these (see attached image). What's shown in the picture was not from my car, it was an image from another thread. But the stud/nut looks similar.

This however looks different from what is shown in the service manual (the service manual shows a inner hex bolt). So do I loosen this with a 12 point socket or a hex key?

I've tried to use a 12mm 12point socket with a regular 3/8 drive ratchet, but it seems to be real tight. The torque spec for the cylinder head bolts are 13-16.5 ft-lbf in the service manual, I thought it shouldn't be this hard to loosen it. Since it is my first time trying to remove the head, I just want to be careful and not force it if I am not suppose to.
 

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It appears someone previously had the engine apart and replaced the head bolts with studs. You should proceed with using a socket to remove the nuts as you'll never get enough torque with an allen wrench.

The factory tightening spec of 13-16.5 ft-lb is only the first step. Another 170*-190* is applied to each through two additional stages. That said, the bolts will be quite tight.
 
Thanks, That's exactly what I needed to know.

I guess I didn't pay attention to the "turning the bolt 85-95 degree twice" part on the next page in the service manual. Thanks for clearing things up.

By the way, now that it uses studs, how would the cylinder head installation procedure be any different? In the manual it talks about measuring the length of the bolts, I guess I don't need to do that anymore?
 
Thanks, That's exactly what I needed to know.

I guess I didn't pay attention to the "turning the bolt 85-95 degree twice" part on the next page in the service manual. Thanks for clearing things up.

By the way, now that it uses studs, how would the cylinder head installation procedure be any different? In the manual it talks about measuring the length of the bolts, I guess I don't need to do that anymore?

Without knowing the details of the actual studs used in your engine, I suggest replacing them with new OE head bolts.
 
They look like ARP studs. You can find torque or stretch information on their web site. They should be better than OE Mazda bolts. That said, most newer cars suggest replacing head bolts when the head is removed and replaced.

http://www.arp-bolts.com/

It's best to use 1/2" drive with a breaker bar for removing head bolts, as mentioned they can be rather tight. If you don't have 1/2" tools get the longest breaker bar you can find for your 3/8" drive tools.

Clifton
 
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