Strange Tapping sound when engine is HOT

[matty74]

I recently had my 3.0 SC motor rebuilt top and bottom, heads and CIS overhauled. I installed a 3.2 oil pump and oil redirection.

I drove it nice and easy during run in and and it runs beautifully and pulls hard.

Now when I sit in traffic and it gets above 180 C it starts to produce a noticable tapping sound at idle and not in gear. I have removed the fanbelt it's not the alt bearing and it sounds like its comming from the lower pully although I can't be sure.

It only does it when it gets really hot, when under power it does not make the sound.

I have all the rod bolts and and internals machined new big and smallend bearings pots redone and new rings etc.. The tapets and cams were re-used.

new chains and rails, re-used oil fed chain tensioners.

Is the 78SC just a noisy motor or is there somthing that was missied.

Matt

[BURN-BROS]

Common noise on the SC, raise your idle a bit.

[matty74]

It already idles at 1100 rpm I think the CIS is running a bit rich

[BURN-BROS]

Then reduce the idle. It is most likely intermediate gear backlash that presents a condition at a certain rpm.