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Hi, last night, while \i waas driving on freeway, my 71 started making this metallic noise and died. It won;t start again, and it seems like something is stuck inside the engine I am assuming timing chain broke and got stuck whatever it's stuck to. How difficult is it to replace timing chain?? I am replacing the cylinder head this weekend anyways, so, I'd like to do this by myself if it's not too difficult. Are there any special tools needed?? Any advice, suggestion, whatever, will be appreciated. Thanks!! It's a 71 with f42 and p90, carbureted.

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The problem with a broken timing chain is that it likes to take other parts with it. Head damage, valves bent/broken, damaged cam, busted pistons. The engine will require a complete tear down.

I hope your timing chain is not busted. You can find out easily by removing the three bolts that hold the inspection plate on the front of the head. Chain is visible.

Or, pull off your valve cover and have a look at things.
 

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Hi -

The previous message had good advice about taking the "inspection cover" off and seeing what was up with the chain. Having a chain go is really a Bad Thing. The cam would stop moving and the crank would keep on going and potentially the piston tops could crunch into the valves that are open.

To replace the chain you need to basically take the front of the engine off. Drain oil and water. Then take out the radiator, fan and hardware, water pump, distributor (after first marking where #1 is) oil pump, crank pulley and harmonc balancer (helpful to have a vise grip chain wrench handy and puller) as well as the oil pan. When removing the cover try not to hurt the head gasket that hangs over.
Details of this are on the "articles" section on ZCar.com . . .just click the link above in case I missed something in my short description above.

Anyway, if the chain is OK, you still have to find out where the noise came from.
You mentioned in your note you are removing your head. Any particular reason?

Steve in NJ
(also working on my timing chain and head)
 

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1st why do you think the engine is stuck?

I have only seen an L series timing chain actually break once. I've seen them jump and punch holes in the timing cover beacause the tensioner failed or the guides broke. The one I did saw break was on an L20B in a 510 and it made a mess big time!
The first thing you should do is pull off your rocker cover and plugs. Line up your engine timing marks ( unless your engine is jammed) If the chain is still around the sprocket and the marks line up do a compression test. If everything is good than it could be distributor or oil pump related. If the chain jumped you have probably hooped all your exhaust valves and you'll need a rebuilt head. If the chain did in fact break then the crank sproket will be hooped, there will probably be a hole in the timing cover with a section of chain hanging out of it, and the head will still need rebuilding. Also, look for a hole in the side of your block, you may have busted a connecting rod which I have done a few times. It's usually obvious by a huge ton of smoke from under the hood! Dig in and have alook.
 
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