3.2 Mechanical Noise That I'm Not Likin!
 

Got my 3.2 top-end overhauled engine back into my '88 coupe this weekend. First start did not go as planned as I had the distributor 360 degrees out of time (what a dunce!). After remedying my embarrassing mistake, the engine started right up (the good side is plenty of pre-lube was obtained from previous starting/cranking attempts).

Here is the problem...there is a rattle coming from the right side of the engine that sounds like it's from the tensioner area. It is at camshaft frequency (i.e., firing frequency) almost like two valves on one cylinder are making noise. The rattle is present at all engine speeds (didn't go above 2000 rpm). I checked and double checked valve lash on assembly and all are set to .004 in. When cranking the engine sounds like compression is equal on all cylinders. When running, engine idles smoothly and all cylinders seem to be firing equally.

I am running replacement 964 camshafts in this engine. When I assembled, I measured cam sprocket distance from the cam chain cover surfaces with both the original, and the replacement 964 camshafts installed. I used the original shims on the appropriate sides and everything seemed to fall back into line. Both cams turned freely in the housings without any binding. I did notice that the left side cam had approximately .010 axial clearance where the right side seemed to have none, yet they both rotated freely. Both cams were timed at .049 inlet lift @ TDC.

Questions-

1) Is it possible that not having cams shimmed properly could make the noise I'm hearing?
2) Can trapped air in the tensioner cause this effect?
3) Is there a proper axial clearance spec on the camshafts?
4) Anything I can do before pulling the engine again?

Help please - getting close to converting to Corvair power!

tensioner
 

loosen the oil line to the tensioner to make sure you have oil pressure to the tensioner then remove the cover and check out the tensioner and chain guides. i recently installed an engine and had tensioner noise. had to replace the tensioner and all is fine now.

We are starting to get more and more of the fail safe Carrera tensioners failing so that is where I would look.
Recheck the exhaust nuts on the bottom of the heads too.
Bruce

Has anyone dismantled a failed newer tensioner to see what it is that fails?

Is there a way to saftey the carrera tensioner against collapse as was done with the old style turbo tensioners?

I read this in another thread. It may pay to contact the OP and ask him about his spacer.

http://forums.pelicanparts.com/911-engine-rebuilding-forum/451191-rebuilding-supercharging-3-0l-2.html#post5145017

Check page 2 of this thread:

http://forums.pelicanparts.com/porsche-911-technical-forum/199819-shops-dont-recommend-carrera-tensioner-update.html

Pretty much lays it down.

andy

I made and installed the "Jerry Woods" spacers when I did a top end rebuild. They likely prevent failures but may not prevent noise from loose chains, of course this depends on how tight you made the spacers.

They say confession is good for the soul so here goes. The noise was due to improper lash setting on one cylinder...lash was about .020 instead of .004. This was confirmed by starting the engine and listening with a stethoscope - the out-of-adjustment cylinder was clearly evident. All valve clearances were rechecked just to make sure that my "senior moment" was only present on one cylinder, and this proved to be the case.

I'm not as good of a wrench as I thought I was. Two mistakes made...distributor out by 360 degrees and lash not set correctly on one cylinder. I do know that all fasteners were torqued properly and double-checked, and hospital cleanliness was maintained.

The engine now starts right up and sounds perfect. Exhaust is clear and no oil leaks. Weather does not allow a test drive today but will report how this goes in a future post.

Thanks to all that answered my questions and offered valuable suggestions - greatly appreciated!

Dave,
You solved your own problem with little or no cost. Excellent!

Mark