1989 Gt Auto Underdrive Kit And Water Pump Bolts

Under drive pullies spin the water pump slower....not always a good idea for the street.

+1 on a don't do it on the underdrive pulleys if you live down south or in any big city where traffic gets bad.

Take a cardboard box, & turn it upside down. Count the number of bolts that hold the water pump on, don’t forget to count the 4 funny looking studs too. Poke a hole in the box for each bolt/stud. Arrange the holes in a circular formation, and mark the box at the 12:00 point. When you remove a water pump bolt, put it in one of the holes in the box according to where it came out of the water pump. When you are done, all bolts will be arranged it the exact same order and position that you removed them from the water pump. That makes re-installing them easy, no wondering where does this bolt go.

A long shank tap should be used to chase the dirt & corrosion out of the original threads before you reassemble everything. Cleaning the threads will help prevent the bolts from seizing next time (yes, there will be a next time).

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.

Long shank 5/16” taps

http://www1.mscdirect.com/CGI/NNPDFF?PMPAGE=267 5/16” pulley tap, 6” shank P/N 04801189

OR second choice, will not clean all the bottom threads unless you grind the end of the tap.

http://www1.mscdirect.com/CGI/NNPDFF?PMPAGE=266 extension tap, 6” reduced diameter shank P/N 04701181

Use lots of antiseize on the bolts to protect them from corrosion and make them easier to remove next time.

See http://totallystainless.net/totally.html for replacement stainless steel 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 $10 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.



Part Number: 23744

Copied from Noobz347

Water pump bolt sizes
*All bolts are 5/16"-18

Water pump:
4 bolts - 3 1/4"
2 bolts - 4 1/4"
2 bolts - 1 1/4"
1 bolt - 2 1/4"

Additional timing cover bolts:
2 bolts - 2 1/4"
2 bolts - 2 1/2"

These are measure from underneath the head to the end of the bolt and NOT from the top of the head. Just the shank.

Sell the U/D pulleys. They are not worth the 5hp at 4000rpm to deal with the cooling and charging problems. If you want your original pulleys to look nice, hit them with either some VHT gloss black or silver enamel for $5

LISTEN to @jrichker and use LOTS of antisieze on all the bolts and studs! If you use the search, you will find many threads where "there is a broken stud or bolt stuck in the block and WTH to do now?" from changing water pumps. And the aluminum cover can corrode too.

The box bolt organizer is either cheating or a slap yourself in the forehead idea.

March sells overdrive pulleys for the alternator. What I ended up doing is only underdriving the ac, power steering and smog pump. W/P and alt are at stock speed.

I used the water pump pulley for the 93 cobra to overdrive it.

The March number for the Alt overdrive is 226 for aluminum and/or 110-08 for black steel.