What size tap to chase 11mm head bolt threads?

58custom · Post by **58custom** » Sat Feb 03, 2007 4:16 pm

I gotta buy one and do the job I should have done when I first screwed this mill together.

Not gonna buy a turbo diesel after all. I rebuilt this engine, I'm gonna run it.

But first I gotta replace the head gasket.

Anybody make head studs for 11mm blocks?

bscutt · Post by **bscutt** » Sat Feb 03, 2007 6:31 pm

The tap is 11mm X 1.5 I just bought one for my '81 project motor and my son's Corrado head swap.

I'm going for the stock bolts, they are more expensive than the 12mm ones (used on my 82) but I haven't seen stud kits. Im sure they're available but probably costly in the 11mm version.

58custom · Post by **58custom** » Sun Feb 04, 2007 12:27 pm

bscutt wrote:The tap is 11mm X 1.5 I just bought one for my '81 project motor and my son's Corrado head swap.

I'm going for the stock bolts, they are more expensive than the 12mm ones (used on my 82) but I haven't seen stud kits. Im sure they're available but probably costly in the 11mm version.

Thanks for the info. I could feel when retorqing the bolts that they were not clamping evenly and sure enough the gasket started to leak and pressurize the cooling system. It was slow at first, I had to add water every few days, but last monday the leak got larger. Chase those threads, folks.

bscutt · Post by **bscutt** » Sun Feb 04, 2007 7:36 pm

I also use anti-seize compound on the threads, just a light coating. I never used to tap out holes or use anti-seize on my old American V8 and inline 6 rebuilds, but there's a noticeable difference when you do. Just proves I'm not too old to learn new wrenching techniques! Now that's standard operating procedure for me.

VWCaddy · Post by **VWCaddy** » Sun Feb 04, 2007 8:53 pm

In place of a tap, you can take one of the old studs and file/grind a groove across the threads and then use that to clean out the threads. It works quite well and will not remove any metal from the existing threads. The groove helps collect the debris that gets scraped off.

Post by **Fatmobile** » Tue Mar 04, 2008 3:05 am

bumpin' it up from the last page

woodrat · Post by **woodrat** » Tue Mar 04, 2008 11:32 am

I couldn't get a tap here locally, you start talking VW and metric at the local parts house and their eyes sort of glaze over. What I did was scrub all the bolt holes out with a wire brush and then cleaned the holes out with q tips, paper towels and rags until they came out pretty clean. I hope that is adequate!

82vdub · Post by **82vdub** » Tue Mar 04, 2008 11:45 am

VWCaddy wrote:In place of a tap, you can take one of the old studs and file/grind a groove across the threads and then use that to clean out the threads. It works quite well and will not remove any metal from the existing threads. The groove helps collect the debris that gets scraped off.

The problem with using a standard tap is that the tap is designed to cut new threads into an otherwise non-threaded hole. If you run a regular tap through your old threads, you will remove more thread material leaving less to grip the new bolts. There are companies that make thread chasting taps specifically to clean existing threaded holes, but don't cut new threads into the opening. However, I have no clue if these are made in the metric size, or the size specifically needed for this job.

woodrat · Post by **woodrat** » Tue Mar 04, 2008 11:55 am

I thought about making one with one of the old bolts, but figured I could get them clean enough with the wire brush and whatnot.

I hope I was right!

surfcam · Post by **surfcam** » Tue Mar 04, 2008 12:11 pm

You can also ask for a bottoming tap. Just gives you another option. Its used to cut thread right to the bottom of a blind hole. In a pinch I have taken an extra bolt and ground three flutes into it. Sort of making a thread chaser. You almost need a die to run over it so there's no burrs. You might be able to clean it up with a small set of thread files. Its one of the tricks I do 60 miles from no where and costumers screaming for their compressor.