bad tappet noise

[clive f]

went to supercar sunday last weekend, car running nice as you like, stopped in services for a pee, came back out and fired up the griff to hear a bad tappet rattle, oil pressure fine, had no option but to continue the trip, and then home afterwards keeping the revs down and load off of the engine.
I found that I had somehow lost an exhaust manifold bolt and also that some of the bolts had come loose, so putting it down to leaking manifold, stripped them down, replaced gaskets, put it all back together and, yep you guessed it still have the tapping noise!
have just had time this evening to remove the rocker covers, then the rocker assemblies, can see no visible indications as to a problem, valves all okay, no marks on them ect, but I have found that if I gently lift each push rod in turn that the suction of the oil just keeps it attatched to the hydraulic lifter, and by lowering it back into place you can feel the oil sticking between the underside of the lifter and the cam lobe, however on three of the lifters on the right hand bank of cylinders you can feel no oil btween the lifter and the cam lobe at all, just a tap as it makes contact.
tommorrow I will remove the inlet manifold and valley gasket to take a good look, but just wondered if anyone has had a similar experience.

the engine had a new cam, lifters, adjustable pushrods, and steel rockers fitted this last winter, and the only recent work done was to refit the valley gasket and the rocker cover gaskets to sort out a couple of annoying oil leaks, bearing this in mind, could some gasket silicon have dropped down and blocked an oil passage feeding the lifters, I would have thought that any excess silicon would just drop down and settle in the sump, and be unable to be sucked up through the oil pickup pipe filter, so considering its all new bits ect, and a very recent oil change, I am thinking it must be oil starvation to one or more of the lifters.

any theories?

Edited by clive f on Wednesday 20th June 20:40

[Ballistic Banana]

New denture glue required Could the actual manifold have a crack in it.

Edited by Ballistic Banana on Wednesday 20th June 21:36

[clive f]

hi Simon, no the manifolds are fine, this noise is so loud, seems to be coming from the cam area I think.

[trackcar]

Silicone blocking the oil pick-up pipe is well known, but you'd expect it to show as a reduction in pressure on the gauge .. it could be that you have a dodgy folower that's not pumping up now for some reason .. does it sound like one individual follower tapping or many followers tapping? Is the noise constant loudness and just varies in frequency with revs or does the noise get louder if you open the throtle and keep therevs the same (ie go uphill and open teh throtle in a high gear so the load on the engine increases but the revs dont increase very quickly) ..

if it varies with throttle position then it could possibly still be a exhaust gasket (listen to all the manifold gaskets with a length of fuel pipe or similar with engine running to try and isolate which is blowing) .. or if it's the same loudness all the time even at tickover thn start looking deeper at the cam and valve train.

joo

[clive f]

thanks Jools, I replaced the manifold gaskets last night, sure they are okay, the noise is there all the time, probably more prominent on lower revs, I think you are probably right about a follower failing, I spoke to dulfords this morning who came to the same possible conclusion, so will strip off the inlet manifold and check it out this evening.

[clive f]

checked it all this evening, guess what, a sodding adjustable pushrod had come loose, so out with the locktite, re check the preloads and lock`em up!!