Rumbling / bearing sound in the engine

[Steve65]

Hi I’m new here and wonder if you can help me. My engine has been rebuilt using new liners/pistons and big end shells, it has had a new chain tensioner also, the main bearing shells and thrusts were all in good condition. When it starts it has good oil pressure and initially sounds ok, then after a few seconds a noise comes and the engine seems to slow down a touch. Having the clutch pressed makes no difference, as does running it for a few secs with the belts off, it is a rumble but similar sound to a belt and pulley noise.‍

 

[jcarruthers2]

Hi Steve

It sounds like it might be the timing chain but you mentioned 'new chain tensioner' as part of the rebuild. I'm hoping you changed the timing chain at the same time as the tensioner as it would be a lot of work taking the engine out again. However, it could well be something else. Would you be able to upload a video of the engine running with audio to the forum? Members have done this before. If we can hear the noise we might be able to collectively work it out. Someone on the forum will probably have had the same problem and recognise the noise.

 

[jcarruthers2]

As an afterthought, it could also be the jockey pulley bearing, common culprit.