AO

I know the institutional knowledge/memory on 16v Euros is a bit thin especially when it comes to whether or not the motors are interference motors or not. I'm here to set the record straight.

Recently one of the Detroit faithful with an 85 Euro had a timing belt failure. Many teeth were stripped from the belt, the tensioner pulley was toast, belt shavings everywhere, you get the picture.

The owner, not knowing any better, tried to restart the motor many many times to no avail.

In comes Davek9 and SueDen (Dave and Dennis) to help the poor soul. They got everything apart, rebuilt the tensioner, got a new timing belt, lined everything up and gave it a start. It ran, but ran poorly and had a definite "miss."

Today a compression test was run. Going from memory the results were something like this.

1: 165
2: 0
3: 0
4: 165

5: 110
6: 0
7: 0
8: 165

So basically, he's got maybe 3 good, 1 marginal and 4 kaput.

Let this be a lesson that 16v Euros are definitely interference engines.

Poor guy.

And for those that know the players here in Detroit, it was not Stan.

pcar928fan

Yea, I don't think anyone questioned that... It is the US 4.7L that may or may not be... That sucks though for sure!!! YUCK!

Drewster67

Rule of thumb - treat ALL Porsche motors as if they are interference engines.

Thanks for the confirmation !!

jpitman2

I thought the break line here was 10:1CR 16V (single dizzy) are NOT interference, everything after that IS interference. Double dizzy 10.4:1CR started in 84 IIRC?
jp 83 (single dizzy) Euro S AT 52k

danglerb

Later Euro S were always considered interference, its the early motors where questions arise due to a piston change I think around 83/84. From the factory it isn't clear the early motors were interference, or at least were ok with being a few teeth off. Suspicion is also that even the early Euro S motor can have carbon build up in the piston pockets making it interference.

The 16v non Euro S motors are not interference, and don't need to be worried about.

AO

See... there is confusion. The '85 Euros are for sure. Can't say about the earlier years... yet.

slate blue

That is right John, 10.1 engines are not interference.

Greg

IcemanG17

Interesting....so only the LH euros are interference....I wonder if its the longer duration cams or high compression pistons that make it that way?

I know for a fact the 4.7L US engines are NOT interference...

mark kibort

having measured the valve depression, i got near .300" to hit the piston. so, it doesnt take a math major to figure out that at .4" lift, or so, you got contact. the valve cuts of the earlier euro were very deep, and would probably clear the pistons, but Ill have to measure the depth. If it is near .15", you would be safe If I was to guess.

mk

hacker-pschorr

Carbon buildup will bend valves in a US 4.5.

I've seen 944 turbos with and without bent valves after a broken belt.

My 944s with 11:1 compression broke the cam chain (same as S4). No valves bent, but both cams were destroyed.

Bottom line, treat them all as interfearence.

Richard S

Early 84 Euro's were built with leftover 83 Euro S pistons. My early 84 Euro broke a camshaft, did not bend any valves.

Rich

blown 87

Very good advice, I have seen more than one non interference engine (not Porsche) bend valves after a belt failure due to carbon build up.
It is just not worth the risk.

Lizard928

I have personally verified at least 1 85 euro is non interference. And 1 84 that is non as well. The 84 had a broken camshaft, and the 85 I tested when doing a belt job. I tried every cylinder at TDC and rotated the cams.
So it could be carbon build up or it could be something had previously been done.

karl ruiter

Honest officer, I was just removing the carbon build up.
My experiences:
US 4.5=Non problem
US 4.5 bottom end with ~80 Euro S top end=Problem

Imo000

Mark me down for a carbon build up, bent valves, '83 US. BTDT