I have an 86 951 with 47k. After 13 DE track days last year, I blew a #2 rod bearing. I then sourced and had rebuilt an 89 951 long block. I added baffled oil pan, mocal oil cooler, pauter race rods, cross-drilled-polished-knife-edge-crank, lightened flywheel and cup car clutch and PP. I put 3k break-in miles and 4 oil changes on the car before heading to the track. After 2 rain sessions and then 1 dry session, the engine was making a bad noise and oil pressure was sporadic. Car was flatbedded to builder. #2 rod bearing failure agian with new new engine. The 89 951 engine is being rebuilt but this time on advice of another builder I am adding a new oil pump (944-107-014-11) and a new oil pressure relief valve (944-107-035-02). I was also told by a different builder to replace the "check valve" aka pressure relief valve located on the head. Paragon shows the part as 944-107-239-01 (#34) on diagram below. I am now told by the builder that this part does not go on the 2.5l engine and is only on the 2.7l engine. Porsche apparently has this wrong on their microfish. Does anyone have any experience with this part on a 2.5l? And if it does go on the 2.5l, should I replace it to offset oil starvation at high RPMs? Any help is as always greatly appreciated. I do not want a 3rd #2 rod bearing failure in 3 successive track days!

 

I believe you're referring to 31, 32, 33 above. 33 is part number 951 104 229 00. My take is that oil comes up from the head under pressure and overcomes the force of the spring, pushes up on the ball and spring allowing oil to go 'round the ball, through the "Pressure Relief Guide" and into the cam housing for lubricating lifters and contact surfaces between the cam and housing. Once shut down or loss of oil pressure, the ball is pushed back down in it's seat by the spring and stops oil from draining out of the cam housing. I think the guide is $8. You have to detroy the old one to get it out.

 

Keith is right and all 2.5L 8V engines have one, can't vouch for the DOHC models. You have to be careful that no metal shavings get in there from head work, if they also decked the top of the head for flatness it can get fouled up pretty easily.

 

can i ask what lubricant you have been using? 2 bearings in 2 track days is no coincidence. you have a problem there.

 

That part is not going to fix a bearing failure problem. Oil is not the answer either unless there wasn't any.

You either have a rod journal on the crank that is not round or #2 rod is not round or both.

 

Well, I just went through this on a 2.7 head. The ball/spring/piston combination has been superseeded (sp) by the one piece part. I spent 2 months trying to source a used one (the one piece unit that you have circled) No one had or would part with one. I ended up buying a new one out of Germany for something like $350. My head was missing the part all together.
Kevin

 

I never had that part on mine, is that bad?

 

I am actually in need of that part as well for a 2.7 head. In my case I just finished my 3.0 8V turbo build and could not get oil to the cam. Finally pulled the cam housing off (today) and pulled the pressure relief valve. It was stuck closed and would not budge. I tried solvents and heat to free it up but the piston would not move even with a hammer and punch. Anyone have one they are willing to part with?

thanks

john

 

Humor me anyway...what oil were you using and at what level? thx
Also targa72e, like to hear of your build if you feel like sharing. Perhaps start another thread.

 

Sorry for the late response, I was traveling. The first engine was using Mobil 1 20w50. The second engine used Valvoline Racing oil strraight 40w for the break-in and then Brad Penn 20w50 for the track. Thanks everyone who wighed in. It would appear that the part I referenced in my first post does not actually go on the 2.5 as porsche shows. Second, parts 31-33 mentioned by Keith E also do not appear to belong on the 2.5. I also pulled the below diagram from Pelican which shows none of the pressure relief parts. Does anyone have any of these parts on their 2.5 951?

 

The two 951 heads I have sitting on my bench and my 83 944 have the pressure relief / check valve in the head. Unless you are talking about something else all 2.5L heads have one. It's an integral part of the lubrication system for the cam and lifters. Without that valve it can result in noisy lifters on startup and cause the seals in the cam tower to leak. It won't cause a rod bearing failure. Just because Pelican doesn't show it doesn't mean much to me. The FSM covers the replacement of these valves very well.

 

targa72e;
The exact same thing happened to me with my 3.0l build.
The valve was stuck in the closed position and wouldn't move. Thank god there was a decent amount of assembly lube present.
We shut the engine off 'cause it was so noisy; my wrench pulled that thing and it was almost like it was seized. I think he took it apart, or something, and freed it up with sand paper. Got it to work properly.
I guess some of these orginal porsche parts are 20+ years old, even if we think we're getting it "new".

 

I received a ball, spring, and piston from both a 944NA and a 994T (yes, they are slightly different) when I was trying to source one for my 2.7 head. These were sourced from Parts Heaven (used). You may want to confirm this with others, but I was told that the old style (ball, spring, piston) was no longer available from Porsche and that the new style (single longer type) was spec'ed as the replacement for the old style. It apparently first appeared in the 2.7 head and then became the replacement for all of the above heads. In my initial search I tried to use the ball, spring and piston type, thinking that if Porsche was now providing it for the 944 and 951 heads, that I could back date and use the old style for my 2.7 head. It did not work that way unfortunately.

 

Incidentally, sounds like there is a small but growing army of 3.0L builds out there?

 

It sounds likea few people have had problems with the pressure relief valve on the 2.7 heads. I checked availability on a new one and the only source I could find was from Porsche. They don’t show any in the US warehouse but have 40 in Germany, cost $350.00. In looking at mine closer I think that it is possible that it corroded internally. The outer housing is steel. My thought is that the head was probably hot tanked, the valve traps some water inside and it corrodes to the point that it will not move. I was only able to get the piston to move in mine using a drift and a hard whack with a hammer. There was no amount of oil pressure that was going to move it. I am going to try and disassemble mine and try and get it working. If that doesnt work i will be ordering a new one.

john