240z Valve Train Tapping After Head Work - VIDEOS Inside

[Hardway]

I can see it. Try F5 a few times ?

 

Hey Bart, I have tried it on 3 different computers at both work and home.  Firefox, Chrome, and IE 8 give almost the same result.  They download the top 10% of the picture and just keeps trying after the better part of 30 minutes.  I can see it is one of my pictures with red arrows and I see the URL is tinypic something.  Can you email me the picture and let me put it on my Photobucket account and link it from there?  I will PM you my email address.  Thanks!

[bartsscooterservice]

Hey Bart, I have tried it on 3 different computers at both work and home.  Firefox, Chrome, and IE 8 give almost the same result.  They download the top 10% of the picture and just keeps trying after the better part of 30 minutes.  I can see it is one of my pictures with red arrows and I see the URL is tinypic something.  Can you email me the picture and let me put it on my Photobucket account and link it from there?  I will PM you my email address.  Thanks!

 ok

[siteunseen]

Hey Bart, I have tried it on 3 different computers at both work and home.  Firefox, Chrome, and IE 8 give almost the same result.  They download the top 10% of the picture and just keeps trying after the better part of 30 minutes.  I can see it is one of my pictures with red arrows and I see the URL is tinypic something.  Can you email me the picture and let me put it on my Photobucket account and link it from there?  I will PM you my email address.  Thanks!

You can't see it post #22 either?  I quoted #21 and it shows the same picture in both, Chrome.  I'll copy and paste it below.

 

Shows up for me, and after looking I can see it has been sprayed with aluminum pain, not bead blasted.

 

[Zed Head]

Works fine on my system.  Windows 7, Chrome, old Compag desktop.

 

The picture shows an arrow pointing at a rocker arm wear pad and a cam lobe.

 

This probably is where the typical, normal, noise happens.  I've pondered where that wear line on the rocker arm wear pad comes from and I'm pretty sure that it's where the pad drops back down (up) on to the cam lobe after it loses contact with the lobe as the high point goes by.  Basically, the rocker arm jumps off the top of the lobe then falls back, clicking every time, and work-hardening that narrow line of contact.

 

Same vein, but not really relevant - notice that many cam lobes are brown and unworn on the base circle.  That's from the mousetrap springs holding the rocker arm down so it doesn't rattle.  On the base circle there is no contact with the rocker arm wear pad.  One easy quick way to get an idea of proper valve lash settings on an old engine.  If it's shiny it may have been a while since lash was adjusted.  Maybe, it's just a clue.

 

Also, and I've seen this discussed before, sometimes the rocker arm wear pad is not ground on the same plane as the rocker arm lash pad contact surface.  So the rocker arm will twist around its own axis as it one wear surface overpowers the other.  The lobe wear surface probably wins until it gets around to the base circle, then the lash pad surface wins.  This can probably cause some noise.

 

For a fairly primitive looking piece, the wear surfaces probably need very precise and accurate work done to get a quiet valve train.

[Hardway]

Thank you for sending me the picture Bart.  I placed it up on Photobucket.  I am not sure since the original location of the picture might be outside the US.  Either way its easy to see now.

 

 

The cam shaft and rocker arms were not replaced and neither were the lash pads.  Before I had all the work done everything was quiet when the engine was cool.  Once the engine warmed up the #4 intake would tap really bad.  I spoke to the machinist earlier this morning and I am going to use my mechanics stethoscope to listen more around the head and engine block.  He has offered to take a look at it and see if we can figure out what is happening.

[Zed Head]

You never really said how the machinist fixed the incorrect machine work n the #4 intake valve seat.  I would guess that he might have shimmed it, since welding and remachining would be very expensive.  

 

And the fact you set lash, but it closed up again is a concern.  Have you rechecked lash again?  Don't assume that things can't keep getting worse.

 

Finally, people that are very confident and say that they have tons of experience and don't make mistakes make me nervous.  Just saying. even the pros can get things wrong sometimes.  Could be that your guy's fix on the #4 valve seat didn't work.

[Chickenman]

One thing that has been mentioned but bears repeating. Carefully examine the wiping area on the rocker arm. Worn rockers will show a distinct line ( or dip ) across the wiping face at about mid point.

 

Edit: If you have a visible line, the rocker should be checked closer for wear.  Drag a finger nail across the line and if you can feel any dip or drag the rocker is worn. Replacement or resurfacing may be required.

 

A rocker arm with a wear dip will never be quiet. The wear line appears at the high point of the Cam lobe at max lift. This is also the maximum pressure point during the cycle. It is often an indication of inadequate lubrication. 

 

Here is a picture of two rocker arms that are worn. Note the distinct wear lines. They will never be quiet unless re-surfaced:

 

Edited June 29, 2015 by Chickenman

[Hardway]

The repair to intake valve # 4 was rather involved.  The reason I was having issues with it was the valve seat had been machined too deep in to the head and the angles were off.  He cleaned up the seat, re-machined it to set the angles correct, and used a valve for a 280z, machining and turning it down to properly fit.  I can now set the lash on it with no issues.  Since the other valves were no sealing correctly I had him replace all the valves, turning them down as needed.  After reading about using 280z valves I checked with him to make sure the valve would not be extending too far and hitting the block.  If I needed to notch the block I could but he assured me they would not as he used my old head gasket as a guide.

 

Later this evening I am going to listen around the head and the block to see if I can pin point the problem valve(s). 

[Chickenman]

 

Has that head been bead blasted?  I want to do mine with glass bead and have it look like that.

 

Thanks,

Cliff

 

 

Try and find a Machine shop that uses a Steam cabinet. This does a much better job than media blasting as it gets into every nook and cranny, including the INSIDES of water passages. Parts are blasted in an enclosed cabinet with high temperature ( 500+ degrees depending on model )  steam from every angle at high pressure.  No damage to finely machined surfaces, so you can clean things like pistons with out having to mask off ring lands etc. And of course there is no media to dig out of little nooks and crannies. 

 

Parts come out looking like brand new..inside and out.

[Zed Head]

Went back and looked at the valve work on the other thread.  Looks like a lot of machine work on those bigger valve heads.  And the seats look bronzish in color.  That's where the problems with lash usually come from, sunken valves due to seat wear.  Seems like a Datsun guy would have recommended new seats.

 

Nobody has mentioned keeping the rockers matched with the cam lobes, but I'd assume you did that, based on your other meticulous work.

 

On the wear lines - I've seen rocker arms with very visible wear lines, that can't be felt at all.  Most builders use feel rather than sight to determine wear.  I think the lines are visible pretty quickly once in use.

 

Don't know enough to say if your guy's on the right path with keeping the seats and modifying valves or if he's way out in uncharted territory.  It's interesting work though.  Good luck.

[Chickenman]

Yes..I meant to include a sentence about dragging a finger nail across the line to " feel " it. I've edited the previous post accordingly.

 

Problem is that sensitivity to feel varies between people. Some people can feel a .001" dip.. Some ( like my Ham fisted buddy )  can't feel .010".

 

Most people can however, see the line, and if a line is visible it's the start of the wear cycle and more checking is required. The two rockers in that particular picture are quite severely worn. Picture came from a thread in which noisy rockers were the issue, and these turned out to be the culprit.

 

Bottom line. If you can see a wear line on the Rocker... check it closer. Particularly if you're having trouble with a noisy valve train. My .02c FWIW.

Edited June 29, 2015 by Chickenman

[Hardway]

Yesterday evening I listened around the head and engine block.  As noted before everything was quiet and consistent at the front of the head and the block.  At the rear of the block just below the head I could faintly hear the tapping sound around #6 and #5 and as I went down it went away.  Everything sounded normal at the skirt of the block.  I went back to the #6 spark plug, placing the lead right above it, this is where I could hear the tapping the loudest.  I moved to the left and right but could not distinguish if it was coming the exhaust or intake valve.  I could also hear some faint tapping on #5 and #4 but nothing like #6.  The sound may be traveling through the head?  Everything on #3 - #1 was quiet.  By the time I was done it was just too hot in the garage to do anything and I did not feel like diving in to a hot engine.  After work and CrossFit today I plan to take the valve cover off and analyze everything on for cylinders 4 - 6.  I could not find how to remove the rocker arms as Geocities on the Atlantic Z site is no more.  Can someone post up how to do it?