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What size inserts are usually placed in a case with 8mm head studs?

FM Former Member
A couple of hours ago I ended up with an AS41 case cut for 94mm cylinders that looks pretty good. Blasted and cleaned, welded and seemingly ready to go, but it has REALLY small inserts in the holes for the head studs.

It came through with 8mm head studs stock, which have been pulled and inserts installed. Nicely done, peened on the inside, the hole chamfered on the face, but the hole diameter is barely bigger than the tiny bolt that holds the tin on the engine or the coil bracket to the shroud.

I mean they're teeny, tiny, teensy, weensy.

Are there heads studs made THAT small that I'm unaware of? I would imagine that they must be Chromoly if they exist at all. Anyone ever run into this kinda thing before?

I'm stumped here. Maybe just trade the case away or scrap it for weight since it's only around $20 a cut to have a case opened locally and if the small studs don't exist, it'll run well over a hundred to have the inserts pulled and 16 hole drilled and tapped for 10mm studs and new inserts installed.

Any help?
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FM Former Member
A couple of hours ago I ended up with an AS41 case cut for 94mm cylinders that looks pretty good. Blasted and cleaned, welded and seemingly ready to go, but it has REALLY small inserts in the holes for the head studs.

It came through with 8mm head studs stock, which have been pulled and inserts installed. Nicely done, peened on the inside, the hole chamfered on the face, but the hole diameter is barely bigger than the tiny bolt that holds the tin on the engine or the coil bracket to the shroud.

I mean they're teeny, tiny, teensy, weensy.

Are there heads studs made THAT small that I'm unaware of? I would imagine that they must be Chromoly if they exist at all. Anyone ever run into this kinda thing before?

I'm stumped here. Maybe just trade the case away or scrap it for weight since it's only around $20 a cut to have a case opened locally and if the small studs don't exist, it'll run well over a hundred to have the inserts pulled and 16 hole drilled and tapped for 10mm studs and new inserts installed.

Any help?
FM Former Member
That's what I was afraid of. I'm going to bring the case halves into the machine shop tomorrow afternoon and have them take a look, see if they can square it away without costing me a ton.

Each bore seems to have a step in it as well which prevents the barrel from bottoming out against the case surface, there's almost an eighth inch of barrel skirt showing. Do they make long and short skirted barrels or am I gonna have to open up the lower part of the cut to remove the step?

Anyone know? Kinda interested, but this case might not be worth the effort or expense to make it right.

Any help at all? Thanks ! !

FM Former Member
"IMHO there is no need for 10mm, they are overkill, unless you are running a turbo."

Didn't the vast majority of VW engines come stock with 10mm studs?

Or maybe just the ones that I've pulled apart over the years.


"I always went straight down,no step . . . "

Yup, that's how my other cases were done. The step looks strange in there. I was hoping that, since it's so far down in the case bore, that I might just clean it out by hand as best I can and the rest of the cut will hold the barrel in place. It's just the last 1/8 that needs to be removed.

Or trim 1/8 from the bottom of the barrel.

OOOOOORRRRRRR . . . . . . . . trash the case and spend a hundred.
FM Former Member
I TOTALLY had my thread sizes wrong, so I can understand.

Luckily the machine shop knew what was going on. Dropped the case off yesterday, went through the problems with it and it'll be ready next Saturday. Cleaned and tested, line bored if necessary, but ONLY if ABSOLUTELY necessary, replace the inserts with 8mm, done.

I guess that the step at the bottom of the bore is OK for regular 94 barrels, I was using a long barrel (longer skirt) to check the bore size, which are meant for a larger stroker crank.

So, thanks everyone. I thought that I'd be pitching the case in the July 4th bonfire, now it's gonna get built up stuffed into the little Fiat for a first test run or two.

I think that I'll try out my "new" side-draft 40DCOE Weber on it; kind of a REALLY strange intake with an uncommon Italian carburetor . . . fitting for such a weird little Italian ride.
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