Newly rebuilt engine with loud tapping noise even at idle?!!?!

[Xnke]

Setting idle with the SU's is easy, if you have them balanced. Just use the idle adjust screw, idle up to 900RPM, set the balance, then use the screw up on the balance tube to up the RPM to 2000, and adjust the balance, back the screw that you upped the idle with all the way out and set idle mix again. Nothin' to it.

[JCan]

That's what Ztherapy prescribes also.

 

I have not yet added oil to the carbs. I also believe SUs are sensitive to vacuum and because the vacuum is is not constant, (due to the cam) I believe it makes idling more difficult.  I guess If I add oil it will help.  I have an email to Steve to ask him what oil weight he suggests I use.

 

I just purchased a timing light.  This weekend, Brian and I will:

  -  time the engine (easy)

  -  install the two oxygen sensors in the 2 pipe of the headers and adjust air fuel mixture (I hope it works, we have narrow band sensors and a multi meter and oscillioscope.

 

Thanks for the advice.!

 

Jim

[clarkspeed]

Did you take the piston/head clearance back to 023?

[JCan]

Both you and my brother want me to remove the custom gasket I purchased (0.063 thickness) and install the stock gasket back in it's place (0.049),

 

Brian and I have a lot of things to do on the car that are of higher importance at this time.    Our plan is to complete the assembly of the car then, once the car is fully running and broken in, revisit:

     - Piston to head height (currently it is ~0.040, with a stock gasket it will be ~0.026 is my best guess given the accuracy of the measurements I made)

     - Cam choice.  Current cam causes the engine to lope too much and the exhaust is loud.

 

I expect we will visit this modification in the summertime this year.

 

We are hoping to complete the drive train this weekend (actually test drive the car even though it does not have hood, hatch, windows, interior etc.) and complete the car in late March.

 

Thanks for asking

 

Jim

[Xnke]

What is your current timing map looking like?

 

With a similar cam grind, my initial timing is 24* initial, and 36* by 3000RPM, running 40* under cruise vacuum. Set idle at 900RPM, and don't expect good torque until 2800-3200, depending on the tune and the rest of the setup...the pull from 3200 in second gear is pretty nice though....

[JCan]

Xnke.

 

I'm not sure what my timing map is however I did have my distributor rebuilt by advanced distributors (17495 Marystown Road - Shakopee, MN 55379 (612)-804-5543).  He not only completely rebult the distributor I gave him, but he retimed it AND checked the vacuum advance for me.

 

Today Brian and I will try to get the car ready to drive for the first time in at liest 12 years (to the best of our knowledge).  We have some work to do, but should have the car ready by 5pm today.

[Xnke]

if it is a stock advance curve, then you won't have 22* initial...more like 12 or 14.

[JCan]

Im adjusting the distributor at 15deg btc without the vacuum advance connected.  I suspect that the vacuum advance will advance it well beyond 22 deg... But I can check tomorrow.

[Xnke]

A stock Z distributor can have anywhere between 10 and 20 degrees of mechanical advance...plus vacuum advance...You might want to start with the factory setting for your year of distributor first.

[Lazeum]

Since I was having the same noise on valve train as the one we can hear on the video, I decided to have a look at my rockers. I thought valve train noise was normal so I was living with it.

 

The following pics are showing you how my rockers & lash pads look like. Out of 12, only 3 are in good shape with expected wear...

All rockers on cam pad look good, shinny & centered. Some seem to not be perfectly straight; is it the result of poor lash pad contact? cam not fully broken in (engine is having 500 mi max since rebuild)? I'm not so concerned but I'll definitely keep an eye on them.

One of them is having a contact pattern at rocker tip which is not symmetrical (pic #4). I think it is not normal so I'll get it modified also.

 

Hopefully, grinding operation on rockers would not jeopardize lash pads dimension requirement. Each rocker is having one specific lash pad. For some reason, base diameter for every cam lobe is slightly different.

Sourcing lash pads at correct thickness from where I am will be a never ended story

 

This goes on Rebello cam with tight lash meant to be set at 0.005 at cam but adjusted at rockers tip at 0.008". Since I check cam clearance at rocker tip, looking at their shape explains why it was difficult to get consistent measurement & adjustments!

 

 

 

 

 

Anyhow, I 'm good for a visit at my machine shop to check what they can do to help.

Thanks also to Jim for his information, it helps to move forwards

Edited May 3, 2013 by Lazeum

[JCan]

Lazeum.

 

I am going to label your pictures 1-4 top left to bottom left then 5-8 top right through bottom right.

 

Lets take a look at the first picture.  Do you notice substantial wear at the edge of the lash pad and little wear on the center?  This means that the rocker is riding on the ridges I spoke of instead of pushing at the center of the valve stem.  It looks like the edges are being worn down rather quickly and by the time we look at image 5, it looks like the wear has sorted itself out.

 

I suggest you file down the edges of the rocker arms to ensure you get contact at the center of the lash pad, then start your engine and warm up the car prior to re-gapping your rocker arms.

 

I will tell you that now, the engine we are running sounds rather quiet.  we have 200 miles on the motor and it is time to pull the valve cover and regap the valves.

 

I can not guarantee that this will fix your problem, but it did fix mine.

 

Best of luck!

 

Jim

[Lazeum]

Thanks Jim for your answer

 

I've been trying to find an engine shop which would be able to regrind the rocker tip with appropriate tooling locally in France.

It is too specific, nobody can do it, even cam shop.

 

Would it be an option to grind those rocker tip by myself? I'm anxious to proceed with such task without controlling parallism of tip surface vs. cam profile.

I could try to make a fixture to help me with such task

 

Only option to make a  clean job would be to ship the rockers overseas to the US. I'll spend twice the money to grind current rockers vs. new units (that would require new custom lash pads most likely)

 

As you said, we can see some wear on the middle of the lash pads showing that contact happens. parts would wear out until they get full contact. So filling down the edges could be an option maybe...

Edited May 6, 2013 by Lazeum

[JCan]

Lazeum.

 

you can grind them yourself it is a simple job using a fine grinding wheel.  Valley head service did it by hand using medium-fine sand paper in a machine very similar to a power sander.  The sand paper was about 2 inches wide.

 

The goal is not to grind the rocker parallel with the lash pad but to grind it with a slight crown that is located approximately in the center of the lash pad..  This will force the rocker to hit the lash pad at one point somewhere in the middle.  Break in of your engine will self grind the crown into a flat.

 

My friends at Valley Head service in LA (http://www.valleyhead.com/) will grind your rocker arms for you.  It shouldn't cost you too much.

 

If money is tight, I suggest you grind  the high point edges off of your rocker arms at a 10 degree angle and not even touch the center of the arm.  I wish I had a picture of the arms after they ground mine.

 

Tell me what you decide to do.

 

Jim

[Lazeum]

I'll probably try to grind them down by myself.

Money is not so tight on my side but I find it ridiculous to spend $100 in shipping for rockers.

 

I've got a grinding wheel at home that should do the trick. I agree with you regarding wear that should self wear the tip to get proper contact. I'll have to keep track of valve clearance to compensate wear over time.

[JCan]

I just realized you were in France.  if you have a file, you can grind the high points (edges) off your rocker arms.  If you do so at a 5-10 degree angle you can watch the edge of the cut progress from the outside in toward the middle.  I would stop once the cut edge passes the high point on the edges because the center of the arm is already parallel with the cam.

 

Remember.  we are doing this just so that you can gap your rocker arms properly.  Gapping is a difficult process,  I gaped mine after the engine was warm and was very careful to gap each rocker arm accurately.  After gapping the engine, it was a bit quieter right after I completed gapping it, and continued to get more quiet as it broke in.

 

Attached is a picture of what I am referring to.

 

Good luck!

 

Jim

 

[Lazeum]

My location is a small detail . It was much easier to work on cars while I was living in Michigan!

 

I would have been tempted to grind the entire width of the rocker. Filing down the edge only should not create any problem with geometry, that sounds obvious but I did not think about it immediately. Your picture makes perfect sense. Thanks!

Edited May 6, 2013 by Lazeum

[Lazeum]

rockers are done! Tomorrow, they're going back on the engine.

It was very easy to do. I've done it with a dremel, only the weight of the tool was enough to grind extra material. The rockers are not that hard.

Since the load to be apply was very small, it is also easy to follow the current shape of the part.

 

I've completed the job with a polishing operation to get smooth surface on rocker tip.

Grinding operation on 9 rockers took me 20 minutes while taking my time to do it right. Polishing took me another 20 minutes. I've spent also some time to get them super clean since burrs were all over the rockers.

So hopefully, it would work.

 

Here are the 3 steps: before => ground => polished.

("Polished" picture is from a different rocker - I was more focusing about the job than on pictures...)

 

 

 

Edited May 10, 2013 by Lazeum

[didier]

Good job, man , but you would prep your rockers like the one in the third picture !   lighter at the lash pad for revs ! 

Edited May 10, 2013 by didier

[JCan]

Lazeum.

 

What you did looks great!  When mine were done, Valley Head Service ensured that there was a slight rake (slope) from the edge to the center of the rocker arm.  This ensured that  the rocker arm touched the valve in the center.  

 

I think that what you did should work!  Good luck with re-assembly.  Be sure you warm up your engine and re-gap it warm.

 

I have my fingers crossed!

[Lazeum]

Me too, I'm knocking on wood. A French translation would be "I'm sqeezing my a$s up"

 

There's also a small rake on the tips. It was also easy to do. Since the dremel tool was a cylinder, I just had to play a little with the angle I was holding the tool. I was able to see exactly what I was doing with the area being ground.