1G Low Compression & Knock

[Jdabishop]

Ok so I initially had low compression on number #3 it was coming out to 70 where as the rest were sky high and perfect. Well then it had a knock later on down the road so I along with others assumed the knock was a spun rod bearing.

Well I just tore down the engine and all the bearing looks great nothing that I see that would cause it. So my question is what else could it be causing the low compression and the knock? I cant think of anything else besides possibly the timing skipped but would that cause an engine to knock?

Thanks,
Justin

 

[Dsmkauai]

Timing being off maybe, could have jumped a tooth. It would cause noise if the valves are hitting the tops of the pistons.

 

[Turbosnatch]

Yes if your valves were hitting the pistons it would sound like a diesel motor. Definately sounds like a timing issue

 

[iceman510]

A bent valve would also explain low compression in that one cylinder. If timing skipped, I would expect damage to all valves/cylinders.

 

[BogusSVO]

You know the cylinder with the issue, #3 Low compression could be from a valve that is not seating properly.

Mic the piston and bore, you may have clasped a piston skirt, or have a wrist pin issue, both of them can cause a knock