Chevy 305 drill / tap question

[SMLEshooter]

I have a running Chevy 305 out of a 1977 Impala that I'm transplanting into another vehicle.

The passenger side head only has one accessory bolt hole, but the alternator bracket from the serpentine system I'm installing has the newer three hole design.

Anybody have experience or advice on tapping two new holes in the cast iron head? My reading seems to indicate I may breach the cooling jacket if I go too deep.

Also looking for any tips or tricks on getting the two new holes in the right spot for proper tensioning...

 

[Plt dinger]

https://www.chevytalk.org/fusionbb/showtopic.php?tid/89525

 

[Cadcom]

Might be easier to pick up a set of heads from a junkyard with the holes already there

 

[Pond Scum]

Make sure to use a tap handle. Not a wrench
Plenty lubricant (WD 40 is fine)
Use a"bottom tap" Flat on the bottom,will help from break thru.
Quality tap. Not HF or Auto Zone
Cut a few threads, clean with compressed air.Repeat
Pretty simple

 

[SMLEshooter]

Got it done. Had to slightly enlarge the holes in the bracket, as I was not perfectly square when I drilled, but it's on.

Thanks for the advice.

 

[harrycalahan]

Got it done. Had to slightly enlarge the holes in the bracket, as I was not perfectly square when I drilled, but it's on.

Thanks for the advice.

Quick tip. Get a thick wall bushing/sleeve that has a slip fit over the tap. Slide it over the tap and put the tap in the hole. Push the sleeve square against the face of the hole and allow it to align the tap as you being tapping. Glad you got it remedied.