Engine squeak

[theunz]

Here's the lowdown. Fresh rebuild on U20 has a fairly loud squeak at idle. It sounds like it's coming from camshaft, around #3 cyl or maybe between 3&4. Sort of an erk erk erk, like its squeaking once per revolution. Removed cam and rockers then reinstalled cam and torqued cam bearings. Cam turns smooth as silk by hand. All rockers show same width swipe mark and all in same location. Nothing looks out of the ordinary. Cam journals and bearing surfaces have minor scoring, nothing that looks like it would be a problem, to me anyway. All valves and guides are new. Journal # 4 (out of 5) has a slight groove in center as does corresponding cap, however the previous cam shows the same groove. Since the old cam didn't squeak, I don't think that's the problem. Engine has about 45 to 60 minutes on it all but about 15 idling. Drove it for about 15 min with revs up to 4500rpm or so with no change in squeak. Any ideas?

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[C.Costine]

Did you run it with the cover off to insure that it is getting plenty of oil? They look a little rough to me.

[bmccarthy67]

As asked above...did you completely wipe all of the oil off for the photos? The cam looks really dry and even if you wiped the lobes the rough cast usually has signed of oil. If it is all new at rebuild, that seems like a lot of scratching for only 60 minutes of total running. My 1st U20 rebuild had the back jack shaft bearing installed wrong and my top end got no oil. Not saying that's what's wrong, but your cam looks really dry in the photos.

V/r
Buddy

[theunz]

Yes cam has all the oil wiped off before pics. All oil galleys working. There are no cam bearings per se on U20 just the machined towers and caps. These have over 100,000 miles on them.

[redroadster]

You may have to rule out what it isn't 1st.
Not the dizzy, flywheel cover,

[Nissanman]

Try running the engine without the fan belt. Guessing it is the water pump or alternator

[bobd]

Spray a fine mist of water at the fan belt before you do anything else.

Squeak usually = belt noise to me.

[theunz]

Already eliminated the water pump and alternator. Wondering if a valve guide could be rubbing valve stem? Anybody ever hear of this?

[sports imports]

We had a similar issue and found it to be rocker arm pad had a high spot where pad and rocker arm are mated. Disconnect coil, hook up remote starter, remove plugs and turn over with cam cover off. This might help locate exact location of squeak.

Ross M

[tjp]

purely thinking out loud here....

Is it possible that is it a chirp from smog hole plug? I assume not but as stated above: "You may have to rule out what it isn't 1st."

[theunz]

Already tried what Ross said but I guess not quite enough rpm that way to make it squeak. Will look closer at rockers, but as stated they all looked the same. Have never experienced the chirp sound that Tim mentioned, but the engine never had the noise before. BTY looks like the previous owner just brazed the end of the plugs and cut off the probe when he removed the smog equipment. Could it possibly be an intake leak, although I would think that would be a constant squeal instead of a intermittent squeak. It is definitely tied to engine rpm.

[tjp]

Unless I am mistaken, unless you have the correct plugs in the smog air inlets, you will get the chirping sound. My 70 2000 had that until I put the correct plugs in the head. The chirping sound does sound like it is coming from the area of the cam shaft.

[sports imports]

new cam , new rockers?

Ross M

[theunz]

Tim, possible, but scince I put most of the 100,000+ miles on the car myself and never heard the chirp before, I'm betting against it, although it's cheaper than a new cam and rockers.

Ross, certainly an option, but hoping not to go that far. Probably easier than popping the head, and could change my B cam for a C...hmmm.

Think I'll try polishing the cam and maybe lightly hit the bearings with some 600 and 1000 grit paper.

[Gregs672000]

Squeak is just a very unusual sound to get from a mechanical operation with oil on it. I'm with tjp... I bet that the air pump port plug is leaking. They are a direct access to a high pressure (piston compression). The wear on the cam looks normal to me, and I assume the rocker pad is ok (?) If there is question about the rocker itself, you could easily replace it with a reground one from the vendors, or have yours resurfaced at a shop that is set up to do it (Delta Cam in Tacoma WA, or Isky in California) but it would be easier to just get one that's already done. If you think there is a high spot, you can use a very light wipe of grease or dry erase marker on the pad, install it, adjust it some (to spec not necessary, don't use a feeler gauge or anything or you'll upset the grease, but tight enough that it runs true without rocking side to side a bunch), spin the cam, remove the rocker and look at the wipe on the pad... should be flat and in about the middle of the pad, no high spot (BTW running off one end or the other of the pad indicates the need for a different size lash cap. Check were your cam is running especially if you just changed cams... could be reground with a smaller base circle which will throw off valve train geometry).

Squeaky guide or seal? Well, maybe. I'll ask my cylinder head guy today as I plan to talk to him anyway. Seems unlikely to me but he would know. The valve guide and seals themselves do not move, just the valve stem moving back and forth. If it were squeaking that bad and that loud I would think the seal would be coming apart. I forget if you did new guides and seals. If its a lube problem then spraying some machine oil in there might give an idea... it's thin and may be able to penetrate better for testing. A little bit of oil gets to the guide and valve stem to lube their operation, but not a lot or you would be burning oil. Spring maybe?