Half the motor lost compression
 

My baby is a 1982 928 stick shift with no motor modifications. Replaced timing belt and water pump about 10,000 miles ago. Using porkensioner. Story goes......
Driving two weeks ago one evening getting on the Palisades parkway with some vigor but nothing crazy. Suddenly the car is running awful. Feels like ignition problem as if missing two cylinders or maybe fuel problem. Limped home and started testing. Long story short...Half the motor has no compression 1-2-3-4 . Checked timing belt, looks good. Timing marks line up everything looks pretty normal. Any thoughts ..........?
Can the head be pulled with the motor in the car?

to be clear,
cylinders 1-4 are on the right side cylinder bank or passenger side, cyl 1 is at the front

cyls 5-8 are on the driverside. cyl 5 is at the front

Usually failures happen when the nose of the Driver Side cam snaps off and then the cam loses timing.

Sorry, this is drivers side. Does that mean cam is seized?

Hi This means the cam has probably snapped off at its snout, remove the bolt and see if the pulley is loose

Same thing happened to a local 928er

Snapped Camshaft at the bolt.

:-(

mike

usually due to overtensioning the belt or over torquing the cam bolt.

' NOTE if the cam is damaged then make sure to use a new cam pulley bolt, torque to spec

Sorry to hear this, good luck with the repair.

After almost a year later finally got some time with my "Baby" Yes, the snout of the drivers side cam snapped. It appears the PKensioner that I install "ratcheted up" and instead applying a tension to the belt just kept taking up slack when there was some and never releasing so it kept getting tighter and tighter. It took a great deal of force to get it to release the belt when I was taking the motor apart. I have to further research what could have gone wrong. Anyone else have this type of experience?
I will keep everyone up to date as I try to figure this thing out.

FWIW the porkensioner will hold the belt at a lower tension than the factory tensioner does,
chances are the cam was damaged previously

When working properly, we don't really have much history on the failure modes. OP seems pretty clear that the belt was too tight.

First step I would take is to look over and take pictures of the tensioner system and see if we can figure out what is wrong.

Actual repair doesn't seem too tough, leave the head on, take off the cam tower housing on that side, put in a new cam and good to go, once the tensioner issues are sorted out.

what we do know is that the Porkensioner holds the belt at a lower tension than the factory part does.
That info is from Ken.

Its quite likely that the cam was damaged prior to installing the Porkensioner ,
unless the cam pulley was pried on an edge during the install of the PK