OK guys, the engine is a LS VTEC, 94 B18B block (81.5 mm) with ITR pistons and B16 (OBD0) cyl. head, with stock cams, valves, retainers & springs, all blue printed 2 years ago with every single clearance checked and so.

Last monday my brother was driving my car and he says the engine started to knock suddenly at normal driving RPM range and throttle, just like if a switch was activated. I checked it out today and I can't really think of the possible source.

I don't really think it could be a rod bearing, causing a rod knock, 'cause oil pressure is perfect and the engine is 2 years old by now with about 40k miles on it maybe more, so if it was a rod bearing I think it'd have happened on the first runs. I've kicked the **** out of the engine along these two years and it runs perfect, great, no blow by, no oil consumpsion and so.
The engine has oil, watter, and everything, it cranks, starts, idles PERFECT, I just haven't got the ***** to drive it like that or floor it. I haven't checked compression either.
My common sense is telling me that it could be the lost motion assemblies which are the stock ones from that 90s cyl. head.
I have to clear out that the cyl head was almost new when I bought it, I mean, it's a OBD0 head but it had no more than 6k miles on it or something, the cam was still black of the heat treatment and the engine from which I took it of was PERFECT. But it's still a early 90s engine so I don't know. I have never replaced the LMAs or anything inside the cyl head so far now.

Thanks in advance.

 

Bad batch of gas or lower grade gas can destory your bearings fast as hell. Ive seen it happen.

 

The engine has always run on 95 pump gas so I don't think that could have been a prob.