Can you tell me how to replace timing chain on a 1966 impala

A loose timing chain might make more noise but not effect way engine runs IF your timing chain slips u could damage engine Car would run rough Hope to help

I wouldn't be surprised if you didn't have to remove the engine/transmission, split the trans from the engine, remove the TC or clutch/pressure plate, (you should have drained engine oil and auto trans oil before doing this), remove the oil pan, remove the rear most main bearing cap, rotate a new seal into place, replace rear main bearing cap, torque, etc. and reassemble.

Worst case you may have to remove harmonic balancer and front timing chain cover, front seal, release all the connecting rod caps and main bearing caps, remove the crankshaft, replace the rear main seal and reassemble. It's a 1966 engine...you should consider replacing the front timing chain with a roller chain as well as rod and main bearing inserts if you have to do all this.

As unlikely as this may be, it may have jumped time. The engine has a timing chain, not a belt....but they can still fail (normally the chain tensioner). A compression check will tell the tale. If there is are multiple cylinders that have low compression, I would suspect the timing chain/tensioner. The backfiring along with the no-start is what makes this suspicious.

You'll need a good repair book or shop manual for this.
You have to remove the timing cover and water pump to access the chain.

This is a 3 to 4 hour job if you know what your doing. Everything on the front of the engine has to come off. These chains rarely go bad or stretch to make an engine run bad. What is the problem you are having?

It Has A Timing Chain. In Fact, Nearly All Of the GM's (If Not All) Have Chains. You Will Mainly Find timing Belts On Foreign Cars Like Toyota's, Acura's, Etc.

Have you checked the starter solenoid? Replace this and see if you're getting fire then. They are usually suspect and the first link in the chain between your battery and the distributor.

Try adjusting the air-feul mixture or just turn the idle up a little bit. For either of these there would be a screw adjustment near carb

Disconnect the battery,Then there shoulkd be a bezel ring on the outside of dash facing you hold the switch from the back and break loose bezel ring it will turn counterclockwise as you are looking at it,make sure the new switch matches, transfer wires from old switch to new and reverse proceedure to install.

sound like you have a bad ground or a bear wire shouting out . it could be in your switch