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S2 Head Swap

Rob,

Thanks. Yes, the bores were much, much better than I was expecting - there was no step that I could detect at the top of the swept area whatsoever, and no scratches or other damage in them. I was very pleased. Given Paul Smiffy's comments at Rutland about his S2 being down on power despite a head change I was fearing the worst but it wasn't the case.

No I didn't clean the pistons. Although the last journey the car did before the head was removed was an 80-or-so mile jaunt to the friend's house and it wasn't done very slowly ... [:)]

I've been meaning to contact you about your Bilstein shocks - did you get to the bottom of the noise they were making and how are you getting on with them? I'm planning on fitting the Bilsteins to my S2 next weekend and and am looking forward to it!


Oli.
 
Went through this about 4 years ago as an inner valve spring broke and its inlet valve eventually kissed a piston. Luckily the bottom end was fine and the cams and cam chain were not affected but the head went it for a full rebuild.
It sounds like you did not remove the intake manifold to give it a good clean. I was shocked how much grime had accumulated at the bottom of the plenum of mine and emptied to cans of brake cleaner to clean it completely.
The adjustment range on the camshaft pulley is wide enough to make for significantly different engine behaviours so I would suggest that you have it checked to make sure the cams are timed to their sweet spot.

I think your S2 is an '89 - does it have the air temperature sensor at the bottom of the inlet manifold like on later S2s?
 
TTM,

No, I didn't think about cleaning the inlet manifold plenum. Interesting that it was full of grot on yours. Well remembered that it's an '89 and yes there is a temperature sensor on the bottom of it (which slightly surprised me when I took it off as I wasn't expecting there to be anything there.)

I simply locked the cams in place with three bolts and didn't tinker with the timing. However I was considering (just yesterday actually!) checking to see how well they are timed. Snag is that I only have one DTI and you need two for the job. Maybe that's one for another day.

Thinking about your broken valve spring and the experience of others (I think that Neil Haughey had one break as well) - have you seen the thread on TIPEC about broken valve springs on S2's?


Oli.
 
As there is coolant warming up the throttle body, presumably to warm up the air when driving in very cold weather, I believe the sensor is here to trigger the cooling fans when the inlet air gets too hot. For years I have wondered why my fans kept running a lot in slow traffic even after coolant temperature was well within check on the gauge, until I spotted this sensor...

As your refurbished head was most likely skimmed while your presumably original head never was, it's possible that the new head may sit a tiny bit lower on the block, which may have increased the static compression ratio, but keeping the cams at the same timing means you may have lost in dynamic compression ratio and may need to readvance them. Your engine might be a very little down in grunt, although that's all theoretical and it's going to be hard to measure an actual difference, but better check the cam timing each time the head is skimmed.

I haven't seen the thread on TIPEC...
 
I'd have expected the cooling fans to be switched by a temperature sensor in the radiator, not the inlet air. Having it in the inlet air would mean that the cooling fans always run in hot conditions, even when it's just been started (unless there is other logic elsewhere) - which they don't. Having said that I can't remember whether there is a temperature sensor in the radiator but I'd expect there to be one somewhere.

I'm not au-fait with the difference between static and dynamic compression ratios. I can understand that if the head moves closer to the block then the valve timing will be retarded slightly as the cam pulley and the main crankshaft pulley are closer together, but this doesn't sound like what you are talking about (and the difference will be minute). Having said that the engine seems, if anything, to be a bit beefier than before. I have get to give it some beans but the mid-range seems more effortless, which is nice. I've put this down to better sealing on the valves although there could be other factors at play, both advantageous and otherwise.

Either way, checking the valve timing is a good idea, thanks!

The Valve Springs thread is here, not on TIPEC - sorry! Link below, but I notice that you have posted on it already.
https://www.porscheclubgb.com/forum/tm.aspx?m=924309


Oli.
 
The sensor on the rad is of course the main driver of the fans but in my case I have noticed the fans would run in warm environment when I am not driving "fast" enough even if the coolant is at 80°C, and that is with the A/C turned off, and all the relays and fuses are fine, so...
 
You can set the timing with one DTI https://youtu.be/rm6d_Ntvgi0
I did it this way two weeks ago. My problem was my dti is not the best but I've got it much much closer than it was before. Also replaced the o rings on my cylinder head oil pressure relief valve. Used generic o rings as Porsche don't sell them separately for the S2.
 
Interesting - I've never read the cam timing procedure in detail in the manual and didn't know it could be done with only one DTI. If you did as described in the film then how did you make the extra probe for the front of the tool? M2.6 isn't a die I have in my die kit!


Oli.
 
This was the problem we had We used a piece of wire bent and stuck to the DTI. Im looking for a longer probe as we speak.
 
Hi Oli,

I never did get to the bottom of the 'clunk' when turning right, although it did get substantially better after having the front alignment done (which was way out after changing the shock inserts, despite best efforts to keep it the same).
I did change the ARB bushes at the same time, so it's hard to tell which precipitated the issue. It does appear to be when unloading the right front suspension that it happens and I can't recreate it by getting the car in the end and levering things around. I can almost feel the 'pop' underneath my feet as though it's something connected to the floor.
Tempted to stick a GoPro camera under the car and drive around so I can see what's moving during the clunk!

Rob
 
Rob I had the same thing. It was the l shaped legs that hold the anti roll bar in place. They are in two pieces with an l shaped part and a c shaped part. I had the c shaped part bolted to the front of one leg and the rear of the other. I changed them both to the front and no more clunk.
 
Aha... maybe that's it then. I couldn't remember how it came off so I think I put the C-shaped part so that the I shaped part was in between the two halves of the C, if you see what I mean. I suppose that means it sits a few mm further back in the car and the arb isn't being gripped quite so tightly.
 
Colin... you're a genius!!! Bolted the ARB in correctly and now no clunking noise! Amazed that it made such a difference!
 
It drove me crazy for weeks.Makes a loud twanging noise. Couldn't believe how such a sm thing could make such a big noise. Glad I could help.
 
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