intermittent knocking?

[Brandon11010]

Alright so i was at the drag strip, made 2 passes, went for gas, came back and heard some knocking from the engine. Fast, fairly loud. but oil pressure good and no metal shavings in oil. Had it towed home, towed it into class to maybe get an opinion on what it might be, started it up and there was no knock.. let it idle, reved it up, nothing.. for about 20 min it was just how it was supposed to.. then bam all of a sudden it starts up, then started to fade away, then started again.. sounded louder underneath the car, so i shut it down.. an instructor told me it could be timing chain loose.. tore the whole thing down and nothing wrong.. rocker arms good.. lifters good, pushrods strait and clear, cam bearings are good..oh and on a side note, the engine has roughly 7000 miles on a total rebuild. but here is where i messed up, i listened to my instrustor as opposed to diagnosing it properly, i.e taking the belt off and starting, cutting out cyl, compression testing... so now its sitting in a friends garage half torn apart and not sure what my next move should be.. renting and engine lift and start tearing into the bottom end? or put it all back together getting all new gaskets and doing it right.. anyone had an intermitten knock before? any suggestions would be greatly appreciated

 

[Evilfox]

You should still be able to be a compression test without the timing chain cover on but that doesn't sound like the problem to me.

Are you sure it isn't detonation? The reason I think this is because you said it did it after you went to go get gas and that is when it started. Also that would be a reason why it took 20 minutes for it to start doing it again. The engine needed time to heat up and thus heat + low octane would cause a knock. It probably sounds worse from the bottom of the car due to it resonating through the headers.

I would recommend you check your plugs for any cracks in the porcelain. That is a sure sign of detonation. Use this link as a reference for checking your plugs.

Century Performance Center, Inc. :: Spark Plug Reading

Also it would be wise to not listen to your instructor. A timing chain won't knock unless it is SEVERELY stretched. What you should have done to check for a stretched timing chain was hook a timing light up and watch the timing marks on the balancer. If the timing mark is steady then the chain is fine, if it bounces around then the chain is stretched. Symptoms would include poor driveability, poor fuel economy, a change in power-range and quite possibly backfiring through the carb or exhaust under WOT.

The cause of a stretched timing chain is also usually improper oil changing habits, fault in your oiling system, or age.