240z Valve Train Tapping After Head Work - VIDEOS Inside

[Hardway]

I got my repaired and re-worked E31 cylinder head back on.  The work was done by a very reputable local machine shop and have full confidence everything was done to the highest quality spec.  You can see what all was done here -> http://www.classiczcars.com/topic/49581-hardways-1971-240z-8011-build-and-repair-thread/page-6

 

With everything back together and the engine running I noticed I had a pretty loud tapping sound from the cylinder head.  Before I ever started the car I did an initial valve job setting everything to factory spec, .008 for the intake and .010 for the exhaust.  Once I heard the tapping sound last weekend I called it a day and came back this morning to do another valve job as I felt I might have missed one.  Sure enough I did, an exhaust valve with no clearance at all.  It easily went in to spec at .010, double checked all the other valves and everything was good. I put everything back together, started the car, and the tapping continues.  It is hard to pinpoint the sound but it seems louder around cylinders 4 and 5.  My original problem was with intake valve #4 so I am unsure if it is actually related or not.  Based on the video clips below does it sound like it is a valve train issue or possibly something else?  I do not believe the valve train should be this loud so I am posting it up here for any feedback or guidance you guys may have.  Thank you in advance!

 

 

[Chickenman]

That definitely sound like noisy valves to me.

 

The cold setting is ( .008" Int/ .010" Exhaust ) just a preliminary step to fire up the engine. According to the FSM a final valve setting should be done with the engine Hot. Hot setting is .010" Int and .012" exhaust,. measured between the Cam lobe Heel and the wiping pad of the Rocker arm.

 

Couple of questions. Stock camshaft correct? Re-ground cams sometimes have slightly tighter clearances required due to profile.

 

All new valves? If you re-adjust the Valve clearances when Hot, and it doesn't quiet down check the end of the Valve stems. Some machinist's will regrind them to get the installed height correct after replacing valve seats or over sized valves. On my old engine, the Machinist  ( not mine ) had ground the Valve tips with what looked to be a Bench grinder. The tips were not even remotely close to being flat. Lash pads would tilt and mess up the measurement

 

That's something to check as a last resort if valve train won't quiet down. A quality Machinist should never make a mistake like that, but isht happens. Never trust anyone is my Motto...

Edited June 27, 2015 by Chickenman

[Chickenman]

If, after thoroughly going over the valve train, and the engine is still noisy, it could be excessive Piston to wall clearance which cause Piston slap.

 

As engine was rebuilt previously, it may have been  bored or honed and the Machinist may have gotten the clearances too big. It doesn't take much. Datsun engines had Hyper-eutectic Cast pistons ( High Silicon percentage ) way back in the 70's. That enabled very tight bore clearances with minimal Piston expansion. Machinists who are used to working on older Domestic engines may not be aware of that. Domestic engines of the day had regular Cast pistons ( Lower Silicon percentage ) that expand more than Hyper-eutectic.

 

My old engine ( which bit the dust ) was apparently rebuilt by some hacker and had huge Piston to wall clearances. The end result was a very noisy engine that sounded very much like the one in your video. The thing is, piston slap can sound almost the same as a noisy Valve-train. my engine had both problems and it sounded like a Mack Truck!!

 

Hopefully that is not the case with your engine... but something to be aware of. Concentrate on the valve train first.

Edited June 27, 2015 by Chickenman

[Diseazd]

Quote.....All new valves? If you re-adjust the Valve clearances when Hot, and it doesn't quiet down check the end of the Valve stems. Some machinist's will regrind them to get the installed height correct after replacing valve seats or over sized valves. On my old engine, the Machinist ( not mine ) had ground the Valve tips with what looked to be a Bench grinder. The tips were not even remotely close to being flat. Lash pads would tilt and mess up the measurement.

Never a good idea to grind the valve stem tips to adjust valve stem height on the L series engines. The early (cupped) lash pads can make contact with the valve retainers and destroy them. The later lash pads are probably ok, because they are flat across the bottom and don't "hang over" the valve stem tip.

[Zed Head]

You said that you lost lash on one valve.  Maybe the valve seat wasn't seated in the head and it dropped in as the engine ran. Not good, but not disastrous unless you burned the valve when you had no lash.  Just a thought.  I know also, that valve lash is lost over time in general as valve seats and valve faces wear.  I'd imagine that some tightening of lash is normal during break-in.  Would depend on what wears more, valve and seat or the cam lobs and rocker wear pads.

[Chickenman]

Quote.....All new valves? If you re-adjust the Valve clearances when Hot, and it doesn't quiet down check the end of the Valve stems. Some machinist's will regrind them to get the installed height correct after replacing valve seats or over sized valves. On my old engine, the Machinist ( not mine ) had ground the Valve tips with what looked to be a Bench grinder. The tips were not even remotely close to being flat. Lash pads would tilt and mess up the measurement.

Never a good idea to grind the valve stem tips to adjust valve stem height on the L series engines. The early (cupped) lash pads can make contact with the valve retainers and destroy them. The later lash pads are probably ok, because they are flat across the bottom and don't "hang over" the valve stem tip.

 

I agree 100%...however, some machinists will still grind Valve stems regardless.

[Diseazd]

Exactly......Another good reason to only use a machine shop that is familiar with the early Datsun heads.

[rossiz]

i've always found that the hot lash adjustment finds quite a few needing adjustment as things move around with expansion. i wouldn't rely on the cold adjustment, it just gets you in the ballpark.

[Hardway]

The machine shop has done many Datsun heads and is very familiar with all American, European, and Japanese engines.  The head has new Manley 280z valves turned down to fit properly in my E31 head along with new valve guides, repaired water holes, and re-surfaced.  It still retains the stock camshaft.  My original problem was that my intake valve #4 had no lash.  After investigating it the valve seat had been machined too far in to the head causing the valve to sit too high and the overall work by the previous machine shop was sub-par.

 

At this point should I check my lashes again and if everything still checks out cold let it warm up and then do another adjustment?  It has not dropped a valve or anything, I guess I was expecting it to be much quieter on my initial start up.

[Diseazd]

What did he do to repair number 4? Did he install a new valve seat? You know that the original bronze valve seats won't last with today's unleaded gas. It needs some steel seats, but that shouldn't cause the noise you're hearing.

[madkaw]

Can't imagine putting in Manley valves and not doing the seats.

There's a good thread on Hybridz about noisy valve trains and lash pads that don't allow the rockers to seat properly.

My rockers were noisy because my rockers were not seating on the lash square.

[Chickenman]

(Snip)

 

At this point should I check my lashes again and if everything still checks out cold let it warm up and then do another adjustment?  It has not dropped a valve or anything, I guess I was expecting it to be much quieter on my initial start up.

Nope... skip straight to fully warmed up engine and check valves hot. Cold setting as per FSM, and as others have noted, is only an INITIAL setting. Just to get you in the ball park. Final setting is to be done HOT.

Edited June 28, 2015 by Chickenman