Help!! Lifter/rocker arm knock?

[steppinsx]

I'm hoping someone can help me with the "noise".I've searched through the threads a few times and still can't figure it out. I have a nasty knock that comes and goes. I can almost produce it at will. It happens when I maintain rpms greater than 3500 or so for longer than say 30 - 45 seconds. I think it is a lifter/rocker arm noise since it will go away if I let it idle at 1k for 10 -15 minutes. It will stay gone as long as I shift at or below 3500 and don't maintain the peak for long. Comes right back if I keep the revs up. There is no power loss at high rpms (actual gains since the port and other mods).It's not the injectors. It's not the timing chain. Both are new. The timing chain guides went and caused a hole in the cooling channel, overheated, warped the head. The head was tanked, milled to flatten it, broken guides replaced, ported, oil channels blown out and the gasket replaced. The timing chain, guides and front cover were all replaced.

My thoughts: 1) Bits of the guides in the oil plugged up the oil channels? Ran Gunk and Seafoam in the oil. Oil pressure is good I think (20@idle, 40@2k, 60@3k).2) Faulty head rebuild? The rocker shaft torque was not correct or even. I retorqured it. The head work was done by a shop that didn't have much experience with Nissans.3) One or more lifters are bad? I couldn't feel any play in the rockers but they were all slightly discolored as though they had been overheated.

I'm thinking now I should replace the rocker arms/lifters. Are these one unit or separate? My Chilton shows them as one but other pics iv'e seen show them as two (the fsm is on the way).

Any help would be appreciated.

89 240sx, n/a KA-e, Injen intake, Hotshot headers, 150k miles

[deviousKA]

The rockers are supposed to be discolored like that, it is from the heat necessary to braze on the rocker pads that run on the cam.

So you just rebuilt the head and installed a new timing kit, after the over heating and busted guides? once those small peices of plastic run into the crankshaft (the plastic dust shavings) they never come out unless the crank is cleaned. This causes bearing problems, but from the sound of it, doesnt seem to be your issue. It does sound like a lifter problem (although not the most common). This may also be a timing chain problem (although its new) check the other post up on top of the board i just replied to on that subject.

Ka24e lifters are difficult to diagnose at times, especially with the on/off situation. I would suspect these, and yes they are one piece. 4 different rocker arms in ka24e they are not all the same. 1/3, 2/4 are the same for the exhaust, and 1/3,2/4 are the same pairs on the intakes iirc.

The lifters/rockers are one piece as well, basically. They do come apart (lifter cylinder held in with small snap ring at the bottom) but if you were to buy them new or used they would come as a complete rocker arm.

[steppinsx]

Thanks, I'll take a look at the timing chain again.

There are a few places i've found that carry the rocker arms; Everything Nissan, Courtesy, AdvanceAuto, you make solid ones. Any recommendations? Good ones, bad ones? What are the benefits/drawbacks of solid lifters?

[RedRain]

I had the same noise on my 280zx turbo one of the lifters would drain out of oil a tick alot. I dont think it is anything to worry about. I drove my car for awhile like that didnt hurt anything but mine. Only did that at idle right when I cranked it up. Weird that yours does it at 3500.

[steppinsx]

Does anyone have a suggestion about choices for replacement rocker arm/lifters and what the advantages/disadvantages of solid lifters are?

[lovemysan2]

If its pumping down while revved I would ,to be safe, run an oil pressure test.

Cheap replacement rocker arms can be had from http://www.nissanparts.cc $21 a piece.

[steppinsx]

Thanks to all for the help.

I replaced all the rocker arms & rocker springs and it revs like hell while purring like a kitten.

Now, what to do with those old rocker arms...

[sil80drifter]

my car ticks strongly at start up (1990 SOHC) for ~5 seconds and then stops. I installed a oil pressure gauge and it shows very low oil pressures (not even close to 20psi at idle) and the FSM says its supposed to be 11+psi at idle. and sometimes the pressure goes lower than even that. i think it' smy clogged passages so i'll seafoam the engine, and i already ordered a higher flow 280zx oil pump, so that should fix it.

sil80

[sil80drifter]

Seafoam didn't do much, except general cleaning. I replaced the oil with 20-W50 which brought the pressure up a bit, but it still dips below the norm. Waiting for the 280zx pump, now that I've developed a rattling between 2.5k-3k rpms, which seems to be the timing chain tensioner not gettign enough pressure/clogged up causing the (replaced 40k miles ago) chain to rattle.

sil80

[TheOne]

heh, that happened when i first bought my '93 240sx. when i revved past 3-3.5k rpm it would sound like if the valves or something were hitting the head, after sometime of bein idling it would also stall. i dissasembled the engine and 1 of the crank timing chain guides was broken into pieces which then went to the oil pick-up, everything else was fine though. i simply rebuilt the engine. car had 108k miles and i allready knew about the knocking, bought it so i can do an rb25det swap later.

[sil80drifter]

in your case it was the original chain hitting the original chain cover. in my case, the chain is hitting the already replaced guides because of low oil pressure, not because the guides gave out.

sil80