mahoney944

Can anyone clear this up for me. I am currently building an 87 944 turbo block which is replacing the incorrect 86 block that was in my car. I noticed my 86 block has an insert in the OPRV hole where my 87 block does not. Does the 87 block use this insert? If so can I just pull it from my old block or is it a different size? I have the correct OPRV for my 87 block just not sure about the insert. Here's pictures of my dirty 86 block with the insert and my clean 87 without it. Thanks.

Dare

I believe the sleeve is not needed in the later blocks with the one piece OPRV. My 86 block had it, but my 88 didn't.

Also if you plan on using an 86 oil cooler housing on a later block with the one piece OPRV, know that there are some minor differences in the castings that make the one piece OPRV not seat correctly. Details, including a fix, in this thread: https://rennlist.com/forums/924-931-...-housings.html

cruise98

The late blocks do not have the sleeve. The OPRV's are not interchangeable between the early and late blocks. Not sure if you can modify them to work or not.

E-man930

Porsche used three styles of OPRVs. Early style 3 piece, late style one piece, (87+ blocks), and a retrofit 1 piece valve to fit all of the 86 & earlier blocks... You cannot mix and match OPRVs outside of their respective intended use.

mahoney944

I have the proper 87 one piece oprv. Was there a change to the oil cooler / filter housing as well? This I'm not aware of?? I know the blocks had differences and I'm aware of the oprv changes. What is the difference in the oil cooler/ filter housing ?

Dare

Check the thread I linked. There's some difference in the thread depth in the housings between the years which results in the late OPRV bottoming out in the hole before it seats on the sealing ring. I had a few threads machined off the end of the OPRV and that fixed it. The last post in the thread shows a picture of the modified OPRV.

That was in 2009. I have since started the engine and confirmed it made oil pressure and didn't leak.

E-man930

I would run a tap through the housing to complete the threads

mahoney944

That seems like the easiest way and prevents future issues if the oprv would fail. Though I may have lucked out on this as my car is an 87. When the original motor failed an 86 block replaced it. I cant remember if I used my 87 housing or if the 86 block had a housing already . If I did use the 87 housing it will already be correct for my new 87 block build...

No real reason but here's the new block money shot with my old 86 block behind it. The old block needs a new home as well! All matching, but cylinders scored, all studs extracted. There was one waterpump bolt that broke coming out. It needs an insert fix. Other wise a nice block for boring or sleeving.

E-man930

Are you going to block fill?

michaelmount123

If you fill the block, do it BEFORE refinishing the cylinders. The cylinders will distort when/while the filler material hardens.

E-man930

+1