Disassembling LT1 down to the timing cover

In another recent thread, someone asked how to get the fan pulley off. I wrote this a couple of years ago and posted it on another board (now slightly updated), but thought it might be of use to someone here too:


There are a great number of tutorials on you-tube and various forums detailing the procedure with photos and video. The Buick varies only in that it may have the mechanical fan to complicate matters (tow pack cars with HD cooling option). But in short, here it is (assuming mechanical fan):

drain the radiator
remove home plate
Unclip sensor wire and vacuum tube from air intake elbow
remove air intake elbow from MAF and TB.
remove fan shroud.
unbolt fan and remove
slack off adjuster and remove fan belt, fan pulley
unbolt 3 long waterpump bolts that also secure fanbelt adjuster bracket.
remove bracket complete with adjuster.
remove nut from waterpump stud securing the air pump bracket.
remove 3 bolts that secure air pump to bracket
disconnect air pump hoses from air box and pipe.
Disconnect wires from bottom of air pump
remove air pump
slack off accessory belt adjuster and release belt from alternator (note: you don't have to remove this belt completely, just get it loose)
disconnect temperature sensor wire from waterpump
disconnect 2 large and 2 heater hoses from waterpump
remove remaining 2 bolts from waterpump
remove waterpump.
remove waterpump spline drive coupler before you lose it.
remove 3 small diameter bolts from harmonic balancer.
Dislodge stamped metal fan pulley. NOTE: it's a press fit. You may need to go below the car and hit the hell out of it with a block of wood. Personally, I heated the hub up a bit with an Oxy-acetylene torch and tapped it off from above.
Remove the 3 large diameter bolts from harmonic balancer.
Remove harmonic balancer.

NOTE: Those last 3 words are so easy to type, but again: it's a press fit. If you do not have the mechanical fan then you may or may not have the three 3/8" tapped holes that the stamped fan belt pulley was bolted to. If you do, then you can use a conventional puller to remove the balancer from the hub. If you don't, then you can choose to get underneath the car with a piece of 2x4 and a big hammer or you can choose to remove the balancer complete with the hub with a puller. If you go that route, then you need to remove the centre bolt from the hub, remove the thick washer, reinstall the bolt 4 or 5 turns into the crankshaft for the puller to push against. You will need a puller with three 7/16" NCT bolts, that thread into the holes where the large bolts where. The puller should have a flat centre. If it's pointed, then touch the centre of the factory bolt head with a drill bit to make a dimple to keep the point centred.

Also, if you have a 96, there may be some extra steps at this point. The 96 has a crankshaft position sensor in there somewhere. I don't so I don't know what extra steps are involved there.

You will need a strap wrench large enough to wrap around the harmonic balancer to keep the engine from rotating while you draw it off. It will gradually get easier and easier and then suddenly harder when it hits the bolt inside. STOP. You now have enough room to remove the Opti. Continue only if you are changing the seal. Remove the puller and retaining bolt. You may have to tap gently with a hammer or find a long 3/8" bolt to finish the job. The 3/8" bolt won't thread into the crankshaft (it's tapped 7/16" NFT)

If you remove the hub, you should replace the seal. If you replace that seal, you may as well do the others too. You will need a special protector to install the infamous waterpump drive seal over the splined shaft. You will need a seal puller to remove the opti drive and crankshaft seals. The seals and waterpump gaskets all come in the Felpro timing cover gasket kit for $9 from Rock Auto. They might not leak today, but it is a lot of work to get to this stage again in the future if they should start seeping next week. OTOH: if you have never replaced seals before, these large diameter ones are probably not the best learning tool. Your call. Anyway: where were we? Oh yeah...

unplug the opti sensor connector.
unplug the opti coil wire
unplug the 4 ignition wires on each side
remove the 2 rubber vent lines from the cap and the body
unbolt the opti 3 mounting bolts
remove opti complete with cap.

NOTE: if you are just changing the cap and rotor, it might be possible to do that in situ. But it's a lot easier on the work bench. There's tiny screws and loose plates sandwiched together, and it's all horizontal at arm's length -- a recipe for disaster, IMHO.

Reassembly is the reverse of the above.

The opti drive seal is a teflon seal (at least, in the Felpro timing cover gasket kit). Teflon seals should be installed dry or they may start leaking. So, lubricate the waterpump seal and the crankshaft seal with a smear of engine oil, but do NOT lubricate the opti drive seal.


Be very careful to orient the opti pin drive correctly. I rotated the engine with the crank (install hub bolt to turn crank) until the pin was at 12 o'clock as the easiest method of pre-setting the opti end of the coupling. The pin engages the larger square hole in the opti. BE VERY SURE YOU HAVE THIS RIGHT. Incorrect assembly could cause permanent damage when the bolts are tightened down. You should not need any substantial force to get the opti mounting points to mate up.

You will draw the hub back on to the crank with the factory bolt -- start without the washer to ensure maximum thread engagement at the start. 1/2 way or so remove the bolt and install the thick washer. Unless you have a 96, it is not keyed in place. On OBD I cars, the optispark takes care of all timing issues so there's no need to orient the harmonic balancer to a specific position.

At this point, you can temporarily reinstall the intake plumbing, reconnect all sensors (including the coolant temperature sensor) and start the car to verify all is OK. Don't run it long without the waterpump and coolant, but you can start it.

Don't forget to install the waterpump drive coupler when you get to that stage. Clean the old gasket material off both the block and the pump and install new gaskets. I used a bit of smurf snot (aka ultra-blue RTV) to help hold the gaskets to the waterpump for assembly, as well as pre-installing the top bolt on each side to keep the gasket in position. If the waterpump doesn't want to slide all the way in place, you may need to turn the coupler slightly to engage the splines.

You will need a special tool to install the waterpump drive seal. It protects the seal from damage as you slide it over the splines.

Here's one for $25 on eBay:
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Here's the official Kent-Moore version (J-39087) for $65:
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Buffman occasionally offers them for $10 on the Impala forum.

A Grade 10 shop class student could whip one up in a lunch hour. Here's the one I made out of a scrap tie-rod end when I changed my opti:

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1.9" long, Minor diameter: 0.550", Major diameter 0.698", Bore .525" x .900"

Some people have even used the cap off a Sharpie marker. You just need something to protect the seal lip when sliding it over the shaft.

Here is a good youtube video of how to use the tool:

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