Carbide bits are very hard, but also very brittle. Any force off center may cause them to break. The warnings about watching the drilling process is very good. If you wander off center with a carbide bit and try to bend it back into position, the bit may break.
Drill bushings are available from machine shop supply houses. The bushing would fit down in the hole in the timing cover and hold the carbide bit on center. The trick is to get the correct size drill bushing. You need to take into consderation both the outside diameter (has to be a snug fit in the timing cover) and the inside diameter (has to hold the carbide bit on center).
The following is a source for drill bits and drill bushings.
Here’s the parts list for the broken water pump bolts. Not cheap, but it will get you fixed and back on the road…
A word about the links, if they don’t work, do a search on the part number (P/N). MSC updates their catalog regularly, and the pages may change, but the part numbers don’t. You will need the Adobe Acrobat viewer which is also a free download –
http://www.adobe.com/products/acrobat/readstep2.html
Carbide drill bits
http://www1.mscdirect.com/ see catalog pages 119-134. Hint" 5/32" is .156 inches, closest number size is 22, which is .157" Generally the spriral flute bits are longer and more expensive. The straight flute bits are shorter and less expensive. Too short a bit and you run out of room to use the drill bushing to center the drill bit in the timing cover.
Drill bushings - you may need a different size, but this is the place to start.
http://www1.mscdirect.com/ Use drill bushing 5/16” OD, 5/32” ID, ¾” long, P/N 07010457, price $8.57 This centers the drill bit in the housing bolt hole so you don’t get off center and damage the water pump, timing cover housing or engine block. Leave the timing cover in place to hold the drill bushing.
A long shank tap should be used to chase the leftover metal out of the original threads. Also recommended to clean the corrosion and dirt out of the threads before you reassemble everything. Cleaning the threads will help prevent the bolts from seizing next time (yes, there will be a next time).
Long shank 5/16” taps
http://www1.mscdirect.com/ 5/16” pulley tap, 6” shank P/N 04801189 price is about $20
See
http://totallystainless.net/totally.html for the bolts. Last time I checked, they didn't have the studs. Nice folks, very into cars of all types. They have all kinds of stainless fasteners for almost every car. The prices are very reasonable, less the $8 for the water pump kit without the studs.
The studs are a Motormite item available at your local Advance Discount auto Parts store.
Motormite Water Pump Stud Kits for Ford, Lincoln and Mercury cars and trucks w/3.8L, 4.6L, 5.0L, 5.8L.
