Author Topic: using 11mm bolt heads on 12mm blocks (Read 3556 times)

ilikevwdiesel · « **on:** February 13, 2009, 08:04:21 am »

anyone ever done it? I wonder if ARP or any other companies make a 12mm stud kit that would work if you drilled out the holes on an 11mm head to the appropriate diameter.

zukgod1 · « **Reply #1 on:** February 13, 2009, 11:02:22 am »

I don't see any reason you couldn't do it.

There is the one hole on the front of the head that the oil travels through that would need to be the correct dia so you didn't starve the head from oil.

ilikevwdiesel · « **Reply #2 on:** February 13, 2009, 11:49:34 am »

Quote from: "zukgod1"

I don't see any reason you couldn't do it.

There is the one hole on the front of the head that the oil travels through that would need to be the correct dia so you didn't starve the head from oil.

you mean the drainback hole in the front center? The 11mm head I have is from a 1.6 it has the large drain hole. The only ones I've seen with a small hole come from a 1.5

truckinwagen · « **Reply #3 on:** February 13, 2009, 02:39:28 pm »

he is referring to the oil feed which is actually in the wall of one of the headbolt holes.
oil travels p along the bolt and into the head through a passage in the wall of the bolt hole.

you would need to make sure that oil would still be able to travel along the shaft of the head bolt/stud.

ilikevwdiesel · « **Reply #4 on:** February 13, 2009, 04:23:52 pm »

Quote from: "truckinwagen"

he is referring to the oil feed which is actually in the wall of one of the headbolt holes.
oil travels p along the bolt and into the head through a passage in the wall of the bolt hole.

you would need to make sure that oil would still be able to travel along the shaft of the head bolt/stud.

oh ok yes duh...I would drill the bolt holes the exact dimension of the 12mm bolt holes in the head I was replacing. I was just wondering if anyone has done this and do they know of any specific stud kits for it. An old geezer told me he had used an ARP kit that was made for a Cosworth or something? I dunno. Maybe ARP has tech support for this :?:

truckinwagen · « **Reply #5 on:** February 13, 2009, 07:09:56 pm »

the 12mm head studs I bought were packaged in a box that said ford cosworth.

ilikevwdiesel · « **Reply #6 on:** February 13, 2009, 07:19:46 pm »

Quote from: "truckinwagen"

the 12mm head studs I bought were packaged in a box that said ford cosworth.

where did you get them? any part numbers?

theman53 · « **Reply #7 on:** February 13, 2009, 07:33:48 pm »

Try the FAQ under ARP part #s

truckinwagen · « **Reply #8 on:** February 13, 2009, 07:55:12 pm »

I got them from headbolts.com
they have a section for vw diesels and have bolts and studs for both 11 and 12 mm heads.

VWSmokr · « **Reply #9 on:** February 14, 2009, 05:12:55 am »

Aren't the 12mm head bolts longer than the 11mm bolts. IIRC the word (OK... maybe it was a rumor!) was that something was changed on the actual block casting to allow the drilling of deeper holes for longer (12mm) bolts. I've drilled & re-tapped for 12mm bolts, but always chickened out & shortened the 12mm bolt to the length of an 11mm. It worked.

A few early 1981 1.6L blocks had the small central oil drainback holes. IIRC all those blocks also had the 11mm bolts.

J.R.
SoCal

ilikevwdiesel · « **Reply #10 on:** February 14, 2009, 12:14:41 pm »

Quote from: "VWSmokr"

Aren't the 12mm head bolts longer than the 11mm bolts. IIRC the word (OK... maybe it was a rumor!) was that something was changed on the actual block casting to allow the drilling of deeper holes for longer (12mm) bolts. I've drilled & re-tapped for 12mm bolts, but always chickened out & shortened the 12mm bolt to the length of an 11mm. It worked.

A few early 1981 1.6L blocks had the small central oil drainback holes. IIRC all those blocks also had the 11mm bolts.

J.R.
SoCal

yes they are longer and the head castings are different, on the 12mm heads the pocket for the head bolt and washer is cut deeper into the head. A machine shop could modify the 11mm head to 12mm dimensions but I'd rather have studs than bolts. Seems if you just enlarged the bolt holes on a drill press it would be all set, just have to get the correct length 12mm stud kit. Supposedly the cosworth ones are just right, but I don't know for sure.