crankshaft key sheared?
 

My roadster let out a very loud back fire and died and will not restart. I have spark, fuel, and compression.
compression #1-75 the other three 65


The only thing found is the timing pointer is about 20 degrees from where should be.


Is possible that the crankshaft key sheared?

Re: crankshaft key sheared?
 

Possible, but not likely. I would start with the basics and check that the top dead center alignment with the cam gear. If good, check for something loose with the dist. When you say "timing pointer" do you mean the dist. rotor cap?

Re: crankshaft key sheared?
 

Sounds like the timing gear sheared off some teeth. I would proceed as stickshift says.

Re: crankshaft key sheared?
 

That's what I was thinking...if "timing pointer" is the cam gear detent, then this is the likely cause (timing gear jumped).

Re: crankshaft key sheared?
 

Check the condenser.

Re: crankshaft key sheared?
 

Does the rotor turn when you step on the starter? If not, timing gear. Rotor might have moved, reset timing see if it will start. Even if it does start there still might be problem with fiber timing gear.

Re: crankshaft key sheared?
 

Assuming when he says he has spark, then he is checking the coil wire while spinning the engine with the starter. That means the distributor is still rotating, ...but out of phase.

My vote aligns with all the other's thoughts in that it has lost the timing gear. A quick check is to remove the timing gear side cover and inspect the teeth. I think you will see the issue. Be sure to remove the engine oil pan to clean the debris out of the pan as that timing gear residue has a nasty habit of plugging the oil pump in a short amount of time.

Re: crankshaft key sheared?
 

I will also vote for a bad timing gear.

Re: crankshaft key sheared?
 

I once had a rotor button that was faulty out of the box. It was too loose on the cam and moved when ever it felt like it to where ever it felt like. That was not good for smooth running!
Check the fit of rotor button on the top of the cam.

Re: crankshaft key sheared?
 

Good call Synchro. Now that you mention that I once had a car with a distributor that would jump out of the slot at the connection at the bottom. It would jump 180 degrees, let out a big backfire and stop. The temporary solution was always to pull up the distributor and reinsert it correctly. The final solution was to replace the worn parts.