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1G 1g 7bolt cylinder head


15+ Year Contributor
Oct 11, 2006
Fairbanks, Alaska

I bought a '91 TSI AWD three months ago. It came with a motor that had no compression on #3 cylinder. The car came with a lot of goodies and I couldn't let it go for the price. The reason for no compression was a couple of bent valves.

The engine has been taken apart. It's a 6 bolt block . The block has been bored/honed/cleaned. The crank has been mic'd and polished. The block already had the balance shafts removed. The car came with a spare head (one of the goodies). After doing some research I have determined that this spare head is a 1g 7bolt head.

After doing some research on here I have determined that the head bolt stud with the teardrop might need to be opened up. I am able to put a 1/2" drillbit half way through every head bolt hole (It stops half way through). The head bolts can go through all the way. The teardrop hole will receive the oil port mod, but I have read that I should also open up this hole so that the 1/2" drill bit goes all the way through. Is this correct? I can fit a 1/2" drillbit from the gasket side, but it stops when it hits the little ridge inside the oil port. Reaming this bolt hole, is it just reaming past that oil galley hole inside the bolt hole? Here is the link to the mod, but I am just making sure before I proceed with this.

NOTE: I am not planning on using head studs. Just the stock head bolts. I measured them and bellow the base of the head they measure 11.84mm(.466") and at the middle of the shank 11.08mm (.437"). Do I still have to ream/drill out the oil feed hole?

Thank you for all your help!
Last edited:


Proven Member
Jul 9, 2013
Anchorage, Alaska
The teardrop hole on a 6 bolt head is 13.95mm or close to that. I highly recommend picking up a set of calipers. It a cheap way to know the exact size of the hole. I currently have a 1g 7 bolt head that has been used on multiple 6 bolt blocks with no signs of oil starvation. The teardrop hole on mine measured 13.43mm (I have no clue if it has been drilled out or not).

Here's a link to a thread where I asked almost the same question.
Hope that helps :thumb:


Proven Member
Jul 1, 2009
Pensacola, Florida
Barza, Its not going to hurt a thing to open up that one hole to .500/13mm
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