[john cross]

I just had my 78 at the mechanics. He told me that there was a wicked "valve knock" coming from it. He then referred to it as "lifter knock". I don't even knoiw what a lifter is. I have noticed this before, but never worried about it. The car sometimes goes through some oil, but the amount is not appreciable.

My questions are; how easy is this to fix; what is a lifter; and, most importantly, how could you isolate the cylinder it is coming from? Is there any way. In looking at the FSM, it says that if you cause a misfire in the cylinder any knocking due to bearings, etc, will go away and that is how you identify the troublesome cylinder. However, I don' think this will help. i can't imagine that a misfire would make any difference.

ANy info would be appreciated. Thanks.

 

[HughskZ]

Re: ?

what L series engines had lifters?......most OHC.........sure noise isn't fuel injectors?

 

[New2Zs]

Lifters are what push the valves open and closed...they are pushed by the rocker arm....off of the cam. If thier is play between the lifter and the arm, you will hear a tick tick tick as the engine idles. It should have solid lifters that require adjusting from time to time. Its fairly easy and you only have to remove the valve cover. But if you have never done this, you might seek the advice of someone that has done it before so that you get it right....the wrong adjustment will make it worse, or float the valves....

 

[ckelly78z]

Exhaust manifold gasket?

Don't forget that a bad / leaking exhaust manifold gasket can cause a loud ticking or knocking sound!

 

[john cross]

Is there a way to identify which cylinder is the culprit??

 

[JoeinCA]

you would want to adjust them all...

it isnt an isolated problem usually... then again it could be a loose timing chain tensioner, i have a nice and audible click from my engine because of this ( 77 280Z)
fuel injectors generally arent that loud...

How many miles? it may be time for a top end, springs, arms, valves...

then again, i coule be way off...

 

[New2Zs]

I'd check the clearance on all of them. Once you have the cover off, you could also check for wear on the cam, and get a small look at your timing chain too. One guy here told me to take a piece of new heater hose and use it like a stethascope and you can move it around the valve cover to find where the noise is the loudest. Don't try to run the engine with the cover off.

 

[john cross]

Well, i have put about 130000 kilometres (80000 miles) on this car since rebuilding the engine. It has vener really run well. Just recently I rewired theignition harness (huge difference) and then replaced the dustributor with one off of ebay (huge difference). I had it at the mechanics doign the distributor. After driving the car, I think h is talkign about a sound that occurs (like a rattle) upwards of 4000 rpm. I had heard this before, but always thought it was a loose exhaust system. it sounds like th eexhaust system is shaking. ANyway, I don't know what the condition fo the top end is. likely, it has hundreds of thousands of miles on it.

 

[yo2001]

If it happens in higher rpm, it may be knocking or a floating valve. try to back the timing back

 

[dufus]

The rattle in the upper rpm can also be caused by a spun rod bearing. You may be able to duplicate the sound by feathering the throttle and revving the engine between say 3000 and 3500 RPM. If that test works and you hear the "rattle" then you can remove one spark plug wire at a time and repeat the test until the "rattle" goes away. The cylinder which is causing the rattle will usually not make the sound when the plug is removed. I went through this with my first engine trying to adjust the crap out of the valves and never removing the "valve noise" It turned out to be a spun connecting rod bearing on cylinder 1. Being my first experience with an L engine I was not accustomed to the higher pitched rattling noise from the spun rod bearing. I was used to the lower pitched knocking at idle from say a small block Chevy.

Good luck,

-Mark