engine problem

[chimalsu]

just changed the rocker gasket today lifted the plenum resealed plenumum tightened rocker fired up no problem tickover smooth every thing ok.went out for run about 15 mile with no problem return home left car running whilst i closed the gates and thought i could hear a noise, lifted bonnet and theres a horrible rattlely knocking noise coming from the top centreish of the engine it does increase with revs but slightly intermittent anyone got any ideas,oil pressure 30 plus level ok not overheating is there anything i could have damaged

[Griffter]

One of the intake trumpets come loose?

[poorpeet]

No tools, nuts, bolts or washers missing after you had refitted the rocker cover were there?

[that daddy]

Is there a chance something as dropped into one of the trumpets?

[chimalsu]

thanks for comments,only thing that could of dropped down trumpets would be silicon or old gasket,was going to devon in her wednesday morning but took the old 944 instead just in case.started her up today and shes sweet went a steady few miles stopped and could hear a slight rattle returned home and let her run for a few minutes and nothing again seems its intermittant