mark kibort

you wouldnt, unless it was already out, and then you would just swap short blocks... much cheaper that a hybrid conversion .
as far as belt failure, its probalby just find if its a US 78 to 82 (4.5 liter) and 80% sure there is no problem with the 83 and 84 US.


i wouldnt bother with it, the stock stuff works great. but, if you got to have it, its seemingly working in a bunch of cars here. dont know about it being race tested though.

you kind of hinted that the valves were close if "carbon" got built up on the valves or pistons and they could "touch".. not so as you know. nothing gets even remotely close unless the belt breaks or slips ....or if you spin it up to 10,000rpm, you might get "float" where the valve is still hanging down and the piston can hit it... but in our motors, thats kind of impossible... and if you drop a valve, it will get hit too, but thats true of all motors, interference or not.

WALTSTAR

Too late, the porkensioner is in the mail! I spoke to Roger who looked up my vin and told me I had the 22nd of 3000 USA 1984 928s and explained that my car had a good many options not normally requested..
I am in da club!

Kiln_Red

Right. I think you misunderstood. What I meant was that I know of occasions with S2 owners who reported bent valves after a belt failure. I also know of S2 owners who reported no bent valves after a belt failure. Clearly, the valves and pistons get very close AT THE LEAST on the S2 if a belt failure occurs. Obviously there are differences between those examples that should explain why one engine bent valves while the other did not. What's the difference besides the obvious fact that the pistons touched over here and not over there? Was there a difference in the dynamics of the engine internals? Valvetrain? Carbon buuldup? Maybe? I don't know. Just a hypothesis.

mark kibort

ah ha.. Yes, i get it . I was misunderstanding your point. I think you are right .
the little changes can make for some problems in engines that normally wouldnt have any upon a belt failure.
I did measure the contact of the valves pushed down in the EURO. with euro S pistons. there was .3" of travel before the valve hit the piston cut out..... if you think about it, if the cut out was .175" , then the valve would hit the piston without it at .125". the lift of the euro cams are about .4", so you can see, that with a 8mm lift US cam, (or near .3") with deeper cuts, it becomes a non interference engine. the euro 80-83 pistons have a .3" pocket., so you can see that any piston with a .3" pocket and up to a .4" cam , will miss contacting the piston, as the distance the valve takes to hit the piston face is about .125.
anyway.... this is all from memory, but i think it gets you in the ball park for the risk involved...... if any. its nice to have a Non-interference engine, because bending valves is a huge pain! (and cost). But i havent heard of too many belts breaking that hadnt required changing if they did fail.

Landseer

You talked to roger so you are good to go.

84 USA #2874 suffered a tb break a few years ago. Stan Shaw had it re-belted. No damage was done. I bought it soon afterward and it runs great. Drove it today.

85 USA #1116. 32 V. Suffered a cam chain derailment last spring. Valves on right bank crashed. Symptoms were a rattling knocking sound up top for 6 months. My dumb *** self drove it anyway without making the effort to diagnose.

Vilhuer

On '84 MY S2 it can be explained by early engines using same pistons as '80-83 S. Those should be non interference like all earlier engines.

Adk46

As I understand it, there are many factors that determine clearance: manufacturing tolerance stack up*, head gasket thickness, carbon build-up, etc..

*e.g., a combination of parts that individually meet dimensional requirements, but combine to produce an undesirable total length not governed by any drawing or specifications, and/or not determined. Long rods, long crank throws, short block, "thin" head, thin gaskets, shallow piston pockets, long valve stems, etc. You can imagine a manufacturer calculating the odds and deciding there's no justification for the trouble of matching parts.

Andre The Giant

+1
I have the porkensioner and love it, peace of mind, for me.

mark kibort

dont think the US 80 to 82 motors came with a 4.7, they were all 4.5 Liter.... the US 83s started using the 4.7 pistons and were all Ljet. the 80 to 83S engines that had a 4.7 , were euro.....and the pistons were different than the 84-85 LHjetronic euro 310hp version engines which had very shallow valve relief pockets. the 300 hp version of the 80-83 euro, had deep pockets, thus giving the compression ration differences of 10:0 vs the 10.5:1 of the later 84-85 euro version.

Kiln_Red

Some MY84 S2 had the early Euro S pistons. I had forgotten about that but that's what Vilhuer was referring to.

mark kibort

I heard that one time as well. curious, as that wouldnt have given the 10.5:1 compression.. maybe the story was , porsche did it and thought no one would notice? if so, you get lucky, that you have a non interference engine, but unlucky in that it would be a little weak. no way around it, as the heads were all the same size for the euro with the big valves. 42 /45mm (exhaust /intake)
they all had about 46cc of volume... just add the gasket and piston cuts and see what you get. (normal 84 piston were 2ccs vs the 80-83 pistons coming in at 7cc)

WALTSTAR

Got the new unit from Roger. The porkensioner is a quality assembly. check it out, you wont be disappointed. I will let you guys know how it installs for me.