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Wjbrooks11

Valve Rockers fell out?

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The same 81 280zx I posted about with 81,000 miles failed my compression test (cylinders 4 and 5 had less than 40psi). I used a bore scope to look inside and cylinders all look good with great crosshatching and the valves seems to be ok from what I can see. I pulled the valve cover and two valve rocker arms were laying loose under the cam, one on cylinder 4 and 5 both of them the one closer to the firewall. Everything looks to be in good shape, no metal shavings chips scrapes or boo-boos lol. The rockers, clips and valve cotter(?) Are in good shape. Why would these fall out? What should inspect/repair before installing so this doesn't happen again? I do notice that the valve rocker pivots are not tight, could it be that simple?

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Edited by Wjbrooks11

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7 hours ago, Wjbrooks11 said:

I do notice that the valve rocker pivots are not tight, could it be that simple?

It could be and/or someone over revved the engine.  Your lucky the lash pads were still up in the head, sometimes they get stuck in the oil drain holes to the oil galley or end up in the pan. Check the surfaces of the rockers, lash pads and cam, make sure there are no burrs or gouges, if not reinstall then, turn the engine over by hand a few times to make sure everything moving smoothly.

 

If you feel the engine stop as your turning don't push it through, reverse the direction just a smidge and find the interference before you proceed any further.

If the engine is rotating nicely then do a valve adjustment, after you're done cycle the engine a few times by hand an recheck all the measurements, readjust anything that needs it.

Start the engine and cross your fingers, loosing a rocker/spring is not uncommon.  These are tough engines, you'll probably be fine.

   

Edited by grannyknot

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It was running but very rich and not very well, I bought it this way last week. Previous owner said it needed valves but with no further discription. The car has new headers and exhaust and a fresh valve cover gasket, so I am assuming someone was adjusting lash and forgot to tighten the intake pedestals for cylinders 4 and 5. All of the other valves were in cold spec and really tight, these two were finger loose.

 

 

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20 hours ago, Wjbrooks11 said:

Another concern is I don't know for sure which rocker was on which valve, I have always read the need to stay in the correct place. Another hope for the best I guess. Looking at the wipe patterns they look the same. 

Well you have 50/50 chance to get it right the first time 😉 Not much you can do but use your best judgement, again you'll probably be fine either way.

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On 11/26/2020 at 7:24 AM, Wjbrooks11 said:

Why would these fall out? What should inspect/repair before installing so this doesn't happen again? I do notice that the valve rocker pivots are not tight, could it be that simple?

 

If the engine has been sitting it might be that the valve stems are gummed up or have surface rust.  They stick, the cam lobe keeps going, and the rocker arm doesn't have any pressure on it to hold it in place.  If it was mine I'd just keep the RPM down for a few hundred miles to let things wear back in.  Although that's not what I did when I got my old had-been-sitting car.

 

See if the wipe pattern looks the same after you reinstall them.  

Edited by NewZed

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I took it out today for the first time since purchase. I have driven alot of S130s, and I have never driven one with this much power. Everything seems to be stock except the headers and exhaust but when I went from 2nd to 3rd (5500 rpms) at about 60 it chirped and acted like the rear tires broke loose. Also did the most ridiculous burnout I have ever done in a ZX, dropped it into 2nd and kept it going for distance. It has killer acceleration and drives like a dream. I'm going to dive in and see what rear diff ratio this has and get under the car to see if there are any clues. The tip to stay in low rpms is a good one, I didn't think about that and was to excited to go for a drive. I'm going to recheck the valves hot after taking a short trip tomorrow. Thanks everyone!

 

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