Thaddeus

Hi,

Since I'm looking to buy a ragged-edge 928 (which, almost by definition will have an old timing belt and WP) to drive home for restoration, I am hoping to learn which year the car's engines became interference. I am interested because of the following logical propositions:

Non-interference = I can drive it 5 miles home with fingers crossed

Interference = flat bed the car with fingers crossed.

Now I'm seeing posts that say, anything after '79 is interference; anything '84 and below, non interference; some say, everything is an interference engine and beware. I don't know who to believe, but I sure don't want to immediately add bent valves to the list of issues as I begin my foolhardy journey.

So what's the authoritative consensus?

thanks

Thaddeus

ViribusUnits

OK, I belive it goes like this. Only for US cars.

78-79 non interference.

80-84 US, zero tollorance. It should be non interference, but there isn't much room. Basicly zero room.

85+ interference

I can attest the the non interferenceness of the 83 cars. I busted my belt realy good, and no contact.

YMMV

hacker-pschorr

There was a thread on this a while ago. If I remember correctly, the general consensus on the 16V US cars was, if the carbon buildup was bad enough, valves could get bent.

Dennis Wilson

Thaddeus,

The official word is that the 16 valve engines are non-interference. A few have reported bent valves but these could have been due to extreme carbon buildup or prior over machining of the head without regard to the warning in the facory service manual.

BTW, there is a kid in the Tulsa area trying to sell his 78 US 5 speed. If interested I will PM his phone number.

Dennis

Thaddeus

Thanks Dennis, but driving her back from OK would be aufbeschlossen.

Thanks for the heads-up guys, I know there's been many threads on the topic but that's why I got flummoxed.

Garth S

"I believe...Official word... General concensus"

So, Thaddeus, are you now certain as to which 16v engines are non - interference? More to the point, are you certain which 16v engines will not experience piston/ valve contact if the TB either breaks or jumps several teeth due to stretching/loss of tension/etc.?
The 928 Int'l catalogue has, and continues to publish (my last copy is vol 12, on pg. 13) exerpts from Kim Crumb, PCA resident tech guru, quoted from Dec., 1996 Panorama as follows...
1) " the only engines which will turn over with a broken or slipped belt and not experience valve- to- piston contact are the 1978-79 engines with 8.2:1 conpression ratio. All other 16v engines, and all 32v engines will experience damage."
...and from point 6) " the belt rarely breaks. Rather, it will stretch, eventually to the point where it may jump one or more teeth..."

The latter point indicates, at least to me, that one cam out of timing and still being driven as a result of the more likely probability of a jumped belt is far more serious than having a broken belt!
Fortunate cases like that experienced by Viribus (with a broken belt) exist: however, until more experienced authorities, two of which are quoted above, support a change of position - I'll continue to treat my 16v engine with the same caution as a 32v , namely that caution appropiate for an interference engine.
If your concern level is cranked up over a '5 mile' drive, I wish I were near to tow you home when you find that 928 that may be on the ragged edge.

Jon F

With the '80-'82 US model's relatively low compression difference compared to the '78-'79 (9:1 vs. 8.5:1, about 4.7cc) and shorter valve lift (10mm/9mm vs. 11mm/10mm) and duration (216/206 vs. 227/216), I find it very difficult to believe that the '78-'79 wouldn't experience valve-to-piston contact but the '80-'82 would. I'll let you know when my timing belt breaks.

Thaddeus

Thanks all. Looks like I maybe need to make a friend with a flatbed ... or put a tow bar on my Honda Accord...

hacker-pschorr

I picture that trip looking something like this:

Garth S

These folks with front wheel drive never learn!! The extra weight for traction has got to go on front..... then the 928 on the rear.