Timing Chain

My 1996 Roadmaster has 249,000 miles on it and it runs great. I am very gentle with it. I need a new water pump. The optispark cap and rotor are fairly new and don’t need replaced. Is there any reason to change the timing chain?

Thanks

Not for daily driver use; plus you'd have to take the oil pan off to do it which is a lot of work.

I'm going through a '96 Impala that needed a lot of maintenance (plugs, wires, AC compressor, optispark, broken exhaust bolts, intake manifold leak and more) and just decided to pull the engine and do all the work with it on the stand. While I did that I also replaced the timing chain, valvesprings, valve stem seals, had the exhaust bolts extracted by a mobile machinist, replaced front and rear crankshaft seals and all timing cover seals. Running the plug wires is a lot easier too while it's out of the car. I also had to rebuild the transmission so why not.

But it has turned into a big project...

Thanks for the response. I am impressed with your project.

Some of these engines have run 500K miles and never been opened.

That is my hope. I get lots of flak from certain friends for driving an old car but it still looks classy, it rides great, runs great, and is paid for. It makes no sense to replace something that isn’t broken, especially when the replacement will be more expensive, less fancy, lighter weight, have higher tag and insurance costs and be just as likely to need repairs. Plus by hanging on to these cars year after year we avoid the hassle of car shopping every so often. Thank you GM!

The only thing a stretched timing chain will do on the LT1s is retard the cam a bit, giving a tad more high-rpm power at the expense of low-end torque.  But it's not significant.

Back to your situation - If you're removing the water pump, before you disassemble the water pump I would take the time to test the optispark vent harness.  With the engine running, remove the little blue elbow from the intake piping and see if it is gently sucking air.  If it is, your vent system is working right and you should be good.  Remove the lower optispark vent hose and see if it's wet inside.  If it is, you'll need to address that sooner rather than later. I have seen optisparks with accumulated liquids inside them.

If you want to go the extra mile, take your opti, clean it, and spray Flex Seal around all the case seals to give a second layer of water resistance.  Then take all the plug terminals and inspect each for any signs of corrosion.  If you see any, clean it out with a pipe cleaner.  Then take dielectric grease and put some around the outside of each terminal and the inside of each plug boot to seal out moisture.  Also check and replace the coil wire if there's ANY evidence of corrosion (you can buy them separately).  Take the 4-pin harness on the passenger side, clean the connector body connection, then spray it with flex seal or if you have access to large heat shrink tubing, put large heat shrink tubing over that connection and then up 4" or so and seal that up.  That will give you a waterproof LT1 ignition system.

If you're feeling super adventurous, pull the harmonic damper, remove the optispark, buy some E-torx sockets from Harbor Freight, disassemble it and loctite the rotor screws inside.  I recently went through half a dozen optispark cores and about half of them had loose rotor screws inside. Then reassemble it, seal it with the flex seal, and reinstall. Make sure the slightly larger of the 3 slots is where the dowel pin goes.

Last trick:  when replacing the water pump, drain the block first either by removing one or both knock sensors OR remove the thermostat housing and thermostat and use a shopvac to suck out coolant.  Much less mess.