Head bolt size for 7 bolt?

[tommiman]

My head bolt size seems to be 13mm 12 point??? I did a search on the forum but everyone either has 10mm hex or a 12mm. I tried with a 13mm 6 point but it slipped.

Does anyone else have 13mm 12 point head bolts?

 

[project_tsi]

My head bolt size seems to be 13mm 12 point??? I did a search on the forum but everyone either has 10mm hex or a 12mm. I tried with a 13mm 6 point but it slipped.

Does anyone else have 13mm 12 point head bolts?

All stock OEM head BOLTS have a 10mm hex head. 6 bolt ARP head STUDS are 12mm diamater, 14mm 12 point head nuts. 7 bolt ARP head STUDS use 11mm diamaters, 13mm 12 point head nuts.

Make sense? It should.

 

[tommiman]

All stock OEM head BOLTS have a 10mm hex head. 6 bolt ARP head STUDS are 12mm diamater, 14mm 12 point head nuts. 7 bolt ARP head STUDS use 11mm diamaters, 13mm 12 point head nuts.

Make sense? It should.

So what you are saying is that I have ARP head studs?

 

[project_tsi]

Yes if you have 13mm 12 point head nuts then you have ARP head studs. Nice little surprise!

 

[tommiman]

Yes if you have 13mm 12 point head nuts then you have ARP head studs. Nice little surprise!

Really? I still can't believe it... I didn't think it would be modified.

Have a look at the pics below to be sure.

Do these look like ARP studs?

 

[project_tsi]

I can't be 100% sure from those pics but they do look like ARP studs. If a 10mm allen head socket drive wont fit in it but a 13mm 12 point socket will fit over it, then yes you have ARP head studs.

 

[tommiman]

I can't be 100% sure from those pics but they do look like ARP studs. If a 10mm allen head socket drive wont fit in it but a 13mm 12 point socket will fit over it, then yes you have ARP head studs.

There is no hole in the centre of the bolts to stick an allen key into. I have to buy a 13mm 12 pt. to be certain but a 13mm 6 pt. fits snug...

Are you certain this is an ARP stud??

 

[project_tsi]

Are you certain this is an ARP stud??

There's only one way to find out! Go out, spend $5 and get a 13mm 12point Deepwell socket, I'd suggest getting it in 1/2in drive also and using it with a breaker bar. If a 6 point fits snug and then pops off, you only risk damaging the nut, do it right, do it once.

 

[tommiman]

There's only one way to find out! Go out, spend $5 and get a 13mm 12point Deepwell socket, I'd suggest getting it in 1/2in drive also and using it with a breaker bar. If a 6 point fits snug and then pops off, you only risk damaging the nut, do it right, do it once.

So I ended up getting the 13mm 12pt and it was too big. Went back and got a 12mm 12pt and it was a perfect fit. I took the head bolts off, but how does that may any sense now?

A 12mm 12pt on a 7 bolt??? The t/b tensioner is from a 2g so it's gotta be from a 7 bolt, but now the head has me confused...???

 

[99gst_racer]

tommiman - Are those studs or bolts?

Judging from those pictures, those look more like bolts than studs. And ARP does not offer a bolt kit for the 4G63 - only a stud kit.

 

[99gst_racer]

So I ended up getting the 13mm 12pt and it was too big. Went back and got a 12mm 12pt and it was a perfect fit. I took the head bolts off, but how does that may any sense now?

A 12mm 12pt on a 7 bolt??? The t/b tensioner is from a 2g so it's gotta be from a 7 bolt, but now the head has me confused...???

That's odd. I was always under the impression that 1G's used the 12mm studs and the 2G's used the 11mm studs. Are you sure your engine is original?

 

[project_tsi]

Hell I dunno. Maybe 2g 7 bolts use 12mm bolts OEM. I've never ripped into a 2g 7 bolt, or looked up the info myself so I guess its possible 2g 7 bolt oem are 12mm bolts.

 

[99gst_racer]

Hell I dunno. Maybe 2g 7 bolts use 12mm bolts OEM. I've never ripped into a 2g 7 bolt, or looked up the info myself so I guess its possible 2g 7 bolt oem are 12mm bolts.

I just physically checked my ARP stock. It is a generation difference, not a 6-7 bolt difference.

The 1G studs are larger in diameter, as well as roughly 1/4" shorter. And the 2G studs are smaller diameter and obviously a little longer.

 

[tommiman]

Here you go guys have a look. I have no idea what the original owner did to this engine but the head bolts are 12mm 12pt. I am the second owner. Have a look at the pics:

 

[wolf20043]

That is a stock 2g stud, the 11mm. The HEAD of it does take a 12mm 12 pt socket, but the threads are 11mm. I have a whole pile in the garage.
Mike

 

[project_tsi]

Thank you Mike for the correct info. I was wrong.

 

[99gst_racer]

^^^ Mike is 100% correct. ^^^

 

[tommiman]

That is a stock 2g stud, the 11mm. The HEAD of it does take a 12mm 12 pt socket, but the threads are 11mm. I have a whole pile in the garage.
Mike

I'm not sure it's a 11mm. I just tried to stick a 11mm 6pt over one of the bolts and it didn't fit. The 12mm 12pt is the only one that fits.

 

[wolf20043]

The 12mm socket is the correct one.
Mike

 

[project_tsi]

I'm not sure it's a 11mm. I just tried to stick a 11mm 6pt over one of the bolts and it didn't fit. The 12mm 12pt is the only one that fits.

No no. The diamater of the bolt is 11mm, and a 12mm 12pt socket fits the head.

 

[wolf20043]

No no. The diamater of the bolt is 11mm, and a 12mm 12pt socket fits the head.

Exactly. Thats what I was trying to say.
Mike

 

[92awddsm]

6 bolt engines have a 12mm headbolt with a 10mm hex in the top of it for an allen bit. 7 bolt engines have an 11mm headbolt with a 12pt 12mm head. This is true for 1g and 2g 7 bolt engines. The 1g 7 bolt uses the exact same bolt as a 2g. The change was made in may of 1992 when they went from the 6 bolt crank flange to a 7 bolt crank flange.

Long story short, you need 11mm head studs.

 

[tommiman]

No no. The diamater of the bolt is 11mm, and a 12mm 12pt socket fits the head.

Oh ok... I'm glad to know that everything is stock here... Suprisingly, the head lifted from the exhaust side with little effot... something is holding it down on the intake side... I'm thinking the A/C compressor... I've already taken all the vac. hoses and elec. connectors off of the intake side...

Any suggestions?