Tapety Noise - Bank 5-8 Newly rebuilt engine?

I have just rebuilt my 308 engine, new exhaust valves, new inlet/ exhaust guides etc and I have set the clearence to the spec in the manual specifically to the upper end of the spec in the manual (to allow for bedding in of the valves in the seats).

Bank 1 -4 sounds fine, Bank 5-8 sounds "very tapety" which I find strange, given my measurements it should not be the valve clearence that is causing this.

Does anyone have any other experience or suggestions as to what might be the issue?

Will wear elsewhere cause this noise?, or could it be something more sinister?

Cheers

Tom

 

Start with compression & leak-down tests on the 5-8 bank, If it looks good, then I' think you're going to have to pull the cam covers & check the valve clearances, suspect that one of the valves is off.

If compression/leakdown shows a problem, it's pull the head again time.

It's also possible that you've got a bad valve spring that isn't bringing the valve up fast enough.

Start with a stethescope to see if you can narrow it down to one particular cylinder(likely), or all of them (unlikely).

If it's all of them, then the only thing I can think of is that you've got a miss-timed cam.

If it's a carb'd car, then maybe the distributor timing is off on that bank.

 

Thanks Verell,

Sure as hell hope I don't have to strip the engine down again. Though at this point I could do it with my eyes closed! Just a bloddy PITA that I will miss the summer again! and burn many hours in the garage again!, was hoping to get a social life back as this engine ate up so many hours over the last year.

My car is the single distrib model and bank 1-4 is fine (nice and quiet) so I don't think it can be the distributor.

I also checked the alignment of the cams to see if something had slipped but all the markings on the outside (which I placed when rebuilding) line up as per when I put the engine together on all 4 cams, so I don't think it is a cam timing issue(unless the cam markings were off put bya mile and a half in the factory!)

I was planning on doing the following next weekend:

1) Get her up to temp and do a compression test. I have the readings taken just before I stripped it down so if there are any signifincant negative variances, that might indicate a problem in one or more cylinders.

2) If there is a problem then do a leak down test and see what we find.......

I suppose the worst case is that there is a dinged valve that is getting touched each time the engine turns over, assuming there is poor spring(but they were all fine when I stripped it down)

Was also going to do an emissions test to see if there is anything abnormal in a specific cylinder. Thought high HC's might indicate an issue.

If all of the above does not throw up anything then I am at a loss indeed!

 

Wasn't going to mention that possibility unless the others didn't pan out, figured you had enough to worry about...
;^)

But, yea, could be that somehow one of the valves has a bent stem, maybe only slightly.

While we're on the worst case sceneros, there's the stray nut in the cylinder possibility...

I know how you must be feeling, been there... There was that infamous ticking noise from JWise's timing cover after we'd got the engine back together & in the car. Kind of a empty feeling sinking down geep in the gut...

 

Stray nut I suppose could be a possibility, but it just sounds too loud. I will put each of the cylinders at BDC and use my telescopic magnet pen to see if I can find anything in there via the plug hole over the weekend.

BTW what did it turn out to be on JWise's car?

 

Had a chat with Ferrari UK, Carlo Fabriazone in the shop to be specific, he has been working on these egines for 30 years.

Apart from what we have mentioned above he indicated the following as possible causes:

1) 1 shim clearence (thickness) out of spec from all others on the bank and as a result appears to be "louder" than all the others when cam hits it.

2) The dimater of 1 shim (not thickness)is slightly narrower than standard so you get slight movement between the shim and the cam follower each time the cam lobe hits it causing the louder noise.

3) Slight distortion in the head when tightening the head so that the cam shaft is not running as smoothly as normally in the caps, will cause a loud tappet like noise - can only be cured by using the Ferrari factory boring tool on the head in situe.

Said he would be surprised if it was 3 or a dinged valve given a complete rebuild.

I will update you when I look next weekend.

 

Tom,

Are you sure it's valve-related? A small hole in the exhaust manifold will make a cute little tapping noise at a frequency equal to 1/2 engine speed. The 308 manifolds did not have the best welding. Mine had 2-3 small holes from incomplete welds, in the 2-into-1 fittings where they were difficult to see.

Tom

 

Tom,



My headers were perfect in fact the one on bank 5-8 had been replaced by the previous owner.

However that point was raised by Carlo, He said if one of the gaskets between the exhaust header and the block had fallen out of place (i.e. only held on by one of the nuts) while putting the header in place then you would get the noise I was describing, so I will be looking at that also over the weekend (before I go taking off the front cam cover) - which will be a joy no doubt!

I would love to know your definition of what " a cute little tapping noise is"

 

Tom,

"Cute little tapping noise" as in a "tick" from a small hole, whereas a large hole would be a louder but rounder sound. I suppose "cute" may not be the best choice in words given what it means in terms of time and expense. The bottom line is that 1mm diameter hole in the exhaust manifold would make a sound similar to a "tap" in the valve train and at the right frequency.

My OEM exhaust manifolds were in good condition and yet they had incomplete welds (factory error) of 1-3 sq. mm that made a tapping noise as above. Worth checking out as a desirable alternative to pulling your heads again.


Tom

 

Unfortantaley I wrapped all my manifolds in glass fibre wrap to reduce the engine bay heat when i had them out, did not spot anything when I was doing this but then again I wasn't particularly looking for holes in the manifold.

 

I don't know how this may pertain to this car, but on the 308 with emission equipment there is an air rail that attaches to each exhaust manifold, and runs up to air pump assembly. I had a small pindole in one of these air rails and it made that exact sound. The exhaust valves are right where it attaches to the manifold. It could be someting as simple as that.

 

As Verell suggested much earlier....

"Start with a stethescope to see if you can narrow it down to one particular cylinder(likely), or all of them (unlikely)."

This will also help to find out if it could be any of the aforementioned exhaust or air-injection rail pinholes, or at least narrow down the general area to concentrate your attention on.

Best wishes,
Bill

 

A long piece of small Dia tubing with one end stuck in your ear and the other end moved around the header junction would probably pin point an exhaust leak. It would be better to have a helper.
Hope its simple--like one of the sniffer tubes.

Best,
Mark

 

FWIW I had the header gasket thing and it isn't really a tapping; it sounds more like a leaf in your exhaust that follows the RPMs. You can tell it's not an engine part if you get close enough while the engine is revving at idle (get a friend!).

Ken

 

Thanks guys, it a European car so no smog equipment which should narrow things down a bit at least.

Will let you know what I find on Saturday.

 

Hi Tom- Sorry to hear about this, I know how you feel.

On my car, the tapping was not valve noise at all. It clearly came from the front timing case/oil pump area and ended up being two things:

1. Verell and I were running the car with the temporary degree wheel still rubber cemented to the front damper. A few weeks later, as the car was running, I scrapped off the cement and paper wheel and the sound almost vanished. So, I stopped the car and removed the rest of the cement from the balance holes drilled in the face of the damper, this reduced the sound even more. The only way to hear it by this time was with a stethescope on to oil pump/timing case area.

Secondly, during the repair of the timing drive bearings, we had to drill out a couple of broken studs and we think a steel chip got into an oil passage and ended up fusing to the timing drive gears off the crank (see below) . So, after removing everything again and cleaning up the gears, the sound was also diminshed.

So, after cleaning up the crankshaft gears, removing the contact cement and degree wheel, and a couple hundred miles- the tapping is gone and all is well.

I hope this helps.

So, on your car, it's clearly from the valve area one only one bank?

jwise
Image Unavailable, Please Login

 

Well I promised to provide an update having tried to find out what the problem was on Saturday morning.

So I got up to the car and started the car.............. no Tappety noise.

I let the car warm up, reved the engine, ........... no Tappety noise.

I took the car out and put about 50 miles on it....... no Tappety noise.

I can only assume that the noise was something to do with the new heads/ valves or shims bedding into place.

So unfortunately I do not have any great nugget of advice on what was causing the noise.

Thanks for all the suggestions.


But as usual getting one of these cars back on the road after a year off is throwing up a number of niggly problems. Another one has arisen with the brake warning light....... making a seperate post on that to see if anyone has had the issue I am seeing.

 

Engines are just freaky. I too have had new engines do simular things, and except in a few rare occasions they turned out simularly.

I have also began to learn as the years roll by, that engines behave almost like plastic, or clay. We think of them as hard sections of metal, yet they are not the solid objects we imagine. And a fully alloy motor, like the Ferrari, is even more so. In the case of checking the crankshaft bore for example, they want both heads bolted down and torqued, and I would assume they mean as well with the liners installed. I would equally assume the gearbox would add some distortion rate and should be considered, although they don't mention it. This is a major reason for going back and retorquing everything, heads included, on as warm of engine you can get to after the first hour, again after the first 100 miles, or at least after the first 1000 miles, and at 30K mile intervals thereafter. It may seem overkill, but the motor likes it and youll have less leaks and general troubles later.

A long time ago I learned that under the proper atmospheric conditions the timing belts could build up a static charge and snap loud enough to be heard inside the cockpit and make you think you have a serious engine problem. I have never heard it, some speculated the belt materials were changed, but I did recently read an article from Gates that suggested it still occuring in some belt designs. From what I recall, it would snap at regular intervals and mimic valve train noise. The fact the noise is mysteriously gone after being loud enough to be a concern would make me suspicious of this phenomenon.