1989 240sx: Hydraulic lifter/rocker noise after replacement

[slayer6o6]

Yesterday I replaced all 12 of my rocker/lifters on my KA24E due to excessive noise from them. I soaked the rockers in a pool of oil for over 12 hours and then installed them, and ran the engine unloaded at 1000 rpms for about half an hour to 45 minutes. The initial noise frightened me so I walked away for about 10 minutes and most of the chattering went away. It sounded much better but some ticking still persisted. Tomorrow I am going to recheck the torque on the rocker shaft bolts to ensure proper torque specs. After driving for about 2-5 hours after initial break-in and the same ticking has returned, and it may be my imagination but the noise seems worse. Car drives seemingly fine and I have my own ideas as to what it could be, and I have a couple of questions that I would like answered, if possible.

1. I was wondering how exactly oil is routed into the lifters, as I saw a small hole in the machined hole in the rocker arm where the rocker shaft goes through the rocker and wanted to understand its significance. Essencially, I want to know how oil travels to the lifters and what, if any, are possible obstruction sites preventing oil from getting to the rocker/lifters.

2. In relation to my first question, could my oil pump be bad? How exactly do you check it aside from an oil pressure gauge, in order to see if it is still functional and working properly (I think that I have answered my own question just now, but still request feedback). Also could my screen on the oil sump be clogged.

3. I also read a forum after my installation that I had not found before the procedure that says that you should not disassemble the rocker shaft bolts/ head bolts/camshaft retainer bolts when the engine is warm as it could cause warping. I replaced the rockers when the engine was still warmed up. Is this true?

4. Does the top of the valves that get met by the lifters by the forward motion of the rockers need shimmed? I have heard of shimming them to reduce excessive play, but that in my opinion does not seem to apply to hydraulic lifter/rocker assemblies due to the fact that they are self adjusting. When the rockers start to make noise due to excessive play they need to be replaced. What is the truth in all of this?

Another bit of information that may be helpful is that for about the first few oil changes that I owned the car I used a K&N oil filter instead of the OEM filter. The rocker noise started sometime after I started using this filter and I quickly discovered that the OEM had a check valve in it and have used it ever since. The initial noise started the first few times when I would cold start the engine and then go away after a few seconds. This progressively got worse over the last year-the noise over time got loader and started to last longer and would happen more frequently on colder days. The oil that I first started running through the engine was Casterol GTX 5W-30, and I switched to 10W-30 still using the same brand and have used it since considering the type of driveing that I do from time to time is higher RPM drifting and rally racing, so the engine sees high revs a couple of times a week, at least, not to mention that this is also my primary daily driver. I figured that the slightly heavier oil would help to protect the engine in these conditions, as well as protecting during routine daily driving. I have also just over a year ago replaced the time chain, guides and tensioner. In the process of the timming chain replacement I used the same pump and the same gasket for the pump

My personal opinion on the whole issue is either I have an obstruction preventing oil flow indicating blocked oil passages, or a failing oil pump/oil pump regulator. I am planning to replace the oil pump with a high/higher-than-stock oil pump such as the '280zx turbo automatic transmission''s oil pump as it has a higher pressure/more flow than the KA24E's stock oil pump. What is your take on this subject also, if you don't mind.

This seems to be a common reoccurance in some SOHC KA's that replace their rockers, and considering that all 12 rockers aren't bought with pocket change, any information or testing procedures along with the requested engine functionality need-to-know information such as the route that oil takes to reach the lifters would be helpful in diagnosing the cause of this problem. Not only is this annoyng, it certainly can't be good for the valves and the lobes of the camshaft.

I have a chilton FSM and it is very vague on the rocker/lifter operation and failure diagnosis. If you have read this far I thank you for that at least that and hope for a informative reponse. I promise that I have done my homework and just want hard to come by information revealed to myself and others that need this for aid in their lifter/rocker troubles. I have dumped hundreds of dollars into my Nissan and this still remains a mystery to me, and tearing the head apart seems to be the only way to get my answers to the flow of oil travel to the lifters. I know this is a long thread but I just want to be able to narrow my 'to check' list down to the true causes so that this issue can be remedied asap. Also any web sites or manuals that would help in my understaning would be greatly appreciated. Thank you again.