I finished putting the engine together yesterday. Today I double checked everything, hooked the battery up, and tried to fire the car.

It will start, but only if you step on the gas, and stay on it. Runs very roughly, at about 450-500 rpms, wanting to die the whole time. Timing is roughly at 4 degrees. I haven't set the timing yet because when I went to do that, I see that its bouncing all over the place. The tan wire was disconnected when I was checking it. It varies back and forth about 6 or 8 degrees. I am using a stock timing chain and balancer, but these same parts had rock steady timing two months ago when the car was running. Any ideas on what could cause this?

Anyways, here is the weird problem... Engine is dead cold. I start it, and pedal it so it runs for about 8 or 10 seconds. When it dies, you can go under the hood and hear a very distinct sound. It sounds like someone taking a hammer and tapping the header. Its not loud per say, but you can hear it from inside the car. This sounds once every two seconds, for about 30 or 40 seconds. I've narrowed it down to #2. If I put my hand on the header tube for #2, I could feel a short and sudden vibration when it makes the sound. If I put my hand on #4 or any other header tube, I can't feel it.

I'm pulling off the valve cover tomorrow to inspect everything, but until then I am very very puzzled as to what can cause something like this.

 

It could be as little as thermal expansion, with the noise generated from the casting and header having a tighter flange fit than the reat of the header, and expanding at different rates. It might even be the head itself, header weld problems, or something that will just go away after a gew geat/cool cycles.

As for the timing varying as you describe, that's usually a result of a worn timing set or distributor. If the engine RPM is not stable and not much above 400, the timing might be wandering as a result of the ECM searching for a running engine.

 

My first thought when I heard it was thermal expansion, but then I wondered if it would get hot enough in the 8 or 10 seconds of runtime to do that. I can't picture enough of a temperature change in that time. I can still put my hands on the headers without getting burnt.

As far as the erratic timing, I am still very confused. This same distributor and timing set were on this engine two months ago before I tore it down, and it was always very steady. Not moving at all. The ECM can't be moving the timing because I disconnected the brown/tan wire for that.

I'll see if I find anything today.

 

This could be a sound of a hydraulic lifter bleeding down.

 

Well, I took the valve cover off this afternoon, and fired the car up for a few seconds. I ran out and put my hand on the rocker studs for #2, and felt a vibration in both the intake and exhaust. They would alternate, each making the same sound, and with each sound, a vibration. None of the other valves did this. However, I did look at the others, and they are LOOSE as hell!!!

I pulled the other valve cover, and the same thing... all the valves are very loose. When I set the valve lash, I moved #1 to TDC and did those valves, then turned the engine 90 degrees, and did #8, and so forth. By the time I did two full revolutions of the crank, all of them were done. I tightened until the pushrod wouldn't turn, then went an additional 1/2 turn.

Its dark outside now, but tomorrow I am going to redo the valve lash. After that, hopefully the noise goes away, and it'll be idling fine.

The only thing I can think of about the loose valves is that maybe the lifters didn't have enough oil inside when I dropped them in. I would think that it would cause the valves to be too tight when they filled up with oil, not too loose. Am I wrong?

 

If you tightened them down that tight, then you drastically overtightened them. You should have tightened them until you felt a drag on the pushrod turning, or there was no up and down play to thepushrod. That is zero lash. I always go one half turn past that. If you overtightened them, and now they are all lose, I wouldnt doubt if you have some cam damage. Definately look into it. I bet you were floating valves early too, with a lash like that.