EuroSquirrel

1980 Euro
I'm having trouble finding timing marks on the cam sprockets. I see some etched lines, but they don't jive with each other or the back cover. The harmonic balancer is light blue, so apparently not original. It has regular timing marks up to 35 BTDC, but then has a pronounced stamped line (like with a chisel) about 45 deg ATDC. This is where the left cam sprocket appears to line up some marks, best as I can tell. I know your supposed to change at 45 deg BTDC, but wonder if 45 ATDC would be the same?! I suppose you can change the belt anywhere as long as the sprockets don't move?!
What say ye?

James Bailey

first off the 45 degree only applies to the 32 valve... your none interference engine you line it up at TDC. The notches marks are on the back side of the cam gears. You need to find them to be sure that you get it right since they may have been wrong before....

davek9

45 deg only applies to 32valve and some higher compression interference engines.

Please post pic's of what you have and also the engine serial number located on the top of block by the center Waterbridge to Water Pump feed (left side looking directly at eng from from front).

edit: ^^^ Jim's got it

GlenL

Ignore the 45 degree stuff as that's for later cars. Your car only needs to be at TDC. The notches are on the back of the cams. The right side is easiest to see. The balancer says "O|T" at TDC...if I recall right.

The cams are under force from the valve springs and will move once you take the belt off. It's not swapping the belt that's the challenge. It's getting the timing set back right.

Once it's aligned, and before removing the belt, make scribe marks on the front of the cams opposite the notches. That'll be easier to work with.

GlenL

All together now!

Mrmerlin

based on the info you also may have the crank damper on backwards,
you should be able to read the numbers while facing the engine .
NOTE posting a picture will increase the quality of the responses you get.

EuroSquirrel

Keep in mind, this is an early euro and doesn't always play by the same rules. I did the belt on a 1980 928S Euro back in the mid 90's. Before the internet and all had had to go by was doing Ford and Porsche 944 T-belts. I don't remember having any trouble finding marks on the 928 as I am now. I'm using left and right looking at the engine from the front.
Engine #M28/16 8115196. I found a V shaped notch on the back of the left gear and it lines up with a raised V in the metal back at TDC. (not much room to see back there) At the same time, there is no notch nor a corresponding raised V on the right side. Pics show the little marks on the front of the gears. Note stamped line around 45 deg ATDC. Everything I'm reading says the 45 deg before TDC is a position that the gears will not move from valve spring tension. Pics to follow...

EuroSquirrel

928 Euro

EuroSquirrel

928 Euro

EuroSquirrel

PS: there is no notch at all anywhere on the right gear. Engine ran well, so go figure :-/

dr bob

Thoughts:

Take a look at the faces of the teeth on those cam gears after you get everything cleaned. From the edge-on pictures, the anodizing is gone from the wear faces, so they are not fit for use anymore. Plus they are the old-style for your [used to be] square-toothed belt. Retrofit the layer round-toothed HTD gears at all positions (crank, oil pump, plus the two cam drive), and use the HTD belt. You'll be sure to have the right index notches on the new gears.

The balancer is fitted in the correct direction, by your pictures. That mark on the left -may- be -45º. You can measure or calculate the circumference of the balancer and divide by 8, should be the distance between the 0|T (0º TDC) mark and that scribe mark if it really is -45º.

Note that stopping the engine at or turning it to show 0|T at the pointer gives you a 50% chance of it ending up at TDC #1 comression stroke, and a 100% chance of it being TDC on the exhaust stroke. Inverse of the logic that causes mathematically-challenged folks to buy lottery tickets, wouldn't you know. Regardless, if the original as-found belt is still on there, the marks will line up with the crank at 0|T, or after rotating the crank another 360º to the 0|T mark again.

Grab the ring with the timing marks on it and try to rotate it a little in place. The failure mode for balancers is failure of the bonded rubber layer betwen the hub and the rim. There's a lip formed in the hub that keeps the ring captive, so it won't come off forward in the car. You might not know that it has failed. If there is any doubt at all, confirm TDC with a pencil or wood dowel dropped into the plug hole. Rotate the crank a little in either direction to see that the piston is at top of stroke when the pointer is looking at 0|T.

EuroSquirrel

Thanks all. Now time to roll the dice. Going to run with the gut feeling that I have it where it needs to be. Just waiting for my flywheel lock to arrive in the mail to get started. Sure is a shame ya have to take the dang balancer off. The Porsche designers had no respect for the poor mechanics that had to work on these cars..! I'll post, in several weeks probably, how it turned out. I have plenty of interior work to keep me busy as well.

ROG100

They should be and look like steel cam gears to me.

SeanR

On my phone so I can't see the pictures well. There is a chance that one of your cams is 180 out. I've seen that a few times.