Sour Kraut's 951

First let me say I have just joined after reading the forums here for the last week or so. I fell you folks here know what is going on so I have decided to stay.

I have searched many threads on this topic and can not find the actual process has been done, or the procedure is carefully hidden. I recently purchased my first Porsche, yeah, and it is a 1986 951 with 86K original miles. My first question to the PO was have the belt and pump been replaced and they could not say. So I was already expecting the worse. The car arrived in better than described condition so I was pleased. I have spent the last few months collect all the necessary replacement parts that it needs. Now I am ready to start and would like to know if an 86 with no auto belt tensioner can be updated with the 87 and later auto tensioner. Needless to say I do not see where the belts or pump has ever been replaced. I have a small leak at the pump so it will be updated to the newer style as well with the belt guide. I never knew the car would run so good without the balance shafts working, my lower adjuster and roller had disintegrated leaving the belt to hang in the wind. Could this be the reason for the shake @ 80? Any help would be great on this. thanks in advance.

xsboost90

yeah def go w/ the updated pump and guide bar. That also takes a different timing belt idler pulley. For the auto tensioner, it can be done but it requires drilling/tapping the front of the block and changing out the belt covers inner and outer to the later style to clear the tensioner. Nothing wrong w/ the non-auto tensioner in my opinion, much easier to change the belt out.

JohnKoaWood

I just pull the tensioner out at the same time.. it is only 3 more nuts...

You CAN update to the newer tensioner, but why? if the old one has worked this long why mess with it?

FWIW, both my 944s have the auto tensionser, so I have not personally dealt with the older ones...

ZV

I'm going to second what xs has said.

As far as the auto tensioner goes, both I and the mechanics I've spoken with feel that the spring-type automatic tensioner is over-rated. Even with the auto tensioner, you still have to re-check the tension at 1,500-2,000 miles and again at 15,000 miles. All the spring-type tensioner does is help you set the tension; it doesn't maintain tension as the belt ages. Also, you're still best off if you check the tension manually and verify it with some other tool. It doesn't really save much (any) work at all.

As far as the balance shafts not running, yeah, that would cause some noticeable vibration. You'll want to fix that as excessive vibration is very hard on an engine.

Sour Kraut's 951

Thanks for the input. So I guess I will scrap the idea of adding the auto tensioner.

I will be replacing everything in front including all seals, as I have purchased everything, is there a difference in the belt kits that say they are for an updated pump versus the belt kits that say they are for 85.5 or 86 or so on? I know my way around mechanics but the Porsche is new to me and I do not want to install the updated pump with the wrong belt and rollers. I read the difference in belts are a 15mm or 18mm, I assume the 18mm is for the updated pump?

JohnKoaWood

Updated kit has a different roller, a guard bar, and a different belt... make sure you have the right stuff BEFORE you start the job as they are not interchangeable....