Knocking sound when priming engine (after rebuild)?

[wazzu70]

Hey guys, I've got a question about an engine I just put together. I have worked a lot with M20s, but this is my first time with an M42 (M50 should be similar I think for this).

I turned the engine over without the plugs to prime it and there was a ticking from the front top near the timing gears. This did not sound like valves on pistons and it was not frequent enough to be this. The sound was more of a loud knock every revolution.

The engine turns freely like it should without binding and I triple checked the timing and everything is fine there.

My theory is that it may be the timing chain tensioner lacking oil pressure. Is this correct? I believe I have read that the M5x motors will do this. Maybe I am crazy?

Any help appreciated here. I would like to figure this out before I try and actually fire the engine up I figured guys here would have experience with this and this is a FI build so I figured it could fit here.

Thanks.

[a32guy]

It could be the chain tensioner simply isn't primed yet-- how long did you crank for? Someone had mentioned in the past, they back-filled the oil pump. Anyone?

[milKt]

So not lifter tick?

[wazzu70]

It could be a lifter since they are hydraulic as well. Does not sound like one though to me but I wouldn't rule it out completely.

I did some more searching and I think it is most likely the tensioner.

I only cranked it for a second or so, then had my dad crank it for a second while I listened for where the noise was coming from. At that engine speed I doubt there are enough revolutions to get a good amount of oil up to the top of the motor.

I will take the valve cover off and take another peek down there and see if everything looks correct while I am turning it by hand.

[Shuasha]

To truly prime the oil pump, you need to pour the oil directly into the filter canister.. I forget if it's the center or the side.

[328iJunkie]

Side

[wazzu70]

Thanks for the tip guys, I will check and make sure I filled the oil canister.