Funny Noise??

swackdog · 07-02-2004, 08:54 PM

A month ago I bought a 81 911SC -- yeah!! After replacing the tranny (2nd gear synchro ring blew out), a new noise appeared in the engine. Loud tapping noise coming from the right side, near the #4 cylinder intake valve cover. Went away 10-15 minutes later. Any ideas what might be happenining?? Sounds expensive.

Jim S
1981 911SC

PJMARKOW · 07-02-2004, 10:53 PM

Take the valve cover off and see if there's a head nut rolling around in there. Could be you have a broken head stud.

Henry Schmidt · Henry Schmidt's Garage

A CIS engine with a few miles on it will have carbon on the heads. It is not uncommon for a piece of carbon to come off the head when the engine is jostled around. When the engine was removed to repair the trans the engine was jostled. This carbon can be severer enough to prevent the engine from rotating. Generally it just passes through the engine causing no permanent damage. It is very common to see this phenomenon in used engines that get transported from point A to point B.
Pull a valve cover and look around but if you can't see anything and the noise is not recurring, don't worry too much.

swackdog · 07-04-2004, 11:37 AM

Henry,

Thanks for your reply. Yesterday afternoon, I pulled off the right valve cover and the problem was obvious -- a broken #5 intake rocker arm. Any other potential problems? Any idea why this rocker arm failed? I have not over revved the engine.

Thanks again,

Jim S

Eagledriver · 07-04-2004, 07:16 PM

I've never heard of the intake rocker breaking. The exhausts break all the time with overrevs at the race track. I'd just replace it and drive it until more evidence of trouble appears.

-Andy

camgrinder · 07-05-2004, 07:21 AM

IF a chunk of carbon was to get in between the valve and piston, preventing the valve from opening, that rocker arm could easily break.
If you just replace the rocker arm, do a compression check and see how that cylinder compares to the rest. If its way off most likely the valve is bent.

briankeithsmith · 07-05-2004, 08:50 AM

Check to make sure your oil spray tube inside the cam housing did not get punctured or compressed.

I broke an exhaust rocker and the rocker piece got wedged into the cam housing oil spray tube and punctured it, as well as compressed it which would have prevented the proper flow of oil onto the cams.

Brian