964TT

It is all custom... Heads, rods, pistons, cams, rockers.
But the deck height is not correct as it is, so it needs to be corrected some way.

Cazzo Super Velo

I can't see why shimming the cilinders woud be a problem, have you asked Waal Garage for an explanation?

964TT

I have no idea either, it seems a simple solution. Waalgarage says you shouldn't do that with 964 engines because of the o-ring on the bottom. So they were just not comfortable with it. They asked another second opinion from a dutch engine revision company they work with and they recommended against it as well.

But when I called with the German supplier of the parts he said they always shim, reason being they want the deck height very precise. Why spend all the money on special parts but not go the extra mile to get the optimal deck height and squish.
Goal being exactly 0.8mm I think.

I believe no engine is the same and with all these custom items coming together there is bound to be a little deviation. So either shim or machine the cylinder depending on which direction you need to go.

You're talking Gt3RSR 4L crank, Pauter custom length conrods, custom pistons, Mahle 102mm cylinders and custom heads in a 26yr old engine case.
Somehow that all has to fit to leave exactly 0.8mm deck height (space between piston and head) for optimal squish.

If anybody has some experience with this and has a strong option on why shims are bad, let me know. I think a custom laser cut shim would be just fine, but I have no experience with this.
Fitting conrods would probably be better, maybe I should check with Pauter if I can exchange.

Cazzo Super Velo

I understand that you need a 1mm shim.
That is too much to blame on tolerances only, so I would think that somewhere in the process of selecting the bits and pieces someone has made a calculation error of 1mm?
Maybe the conrods are 1mm too long or the position of the pistonpen (is that english?) is not correct.

964TT

Probably around 0.8mm, but better to have fitting rods.

964TT

evoderby

Hi Thomas, I have no idea on the pro's and cons I'm afraid but would love for Colin to chime in....where are you batman?;-)

From a theoretic perspective on a single cilinder engine I see no problem with shimming, on a multi cilinder engine that shares a single camshaft the answer whether shimming is right or wrong is a bit more complicated as it depends on why shimming is needed.

When the top face of the cilinders is leveled out through shimming this seems good news since all three cilinders have equal height / are on a level plane , bolting on the cilinder heads should now create equal height in turn to mount the cam housing against. However when shims are used the equal out variance in rod length, piston height etc. which in turn leads to unequal cilinder deck height / unequal plane amongst the three of them the cam housing will distort when bolting things on top op the cilinders....not good.

Again, the above is just me theorizing....

964TT

Thanks for your thoughts, appreciated.

Yes, shimming the cylinders differently would be bad. I get that, but thats not the idea here. Measure one, apply the same shim to all.

I contacted a few others and one engine builder in the US said no problem to shim a 964 engine and another one in Germany said change the parts, don't shim. I lean towards the last, like Frank said the build is too bespoke to cut corners.

Juha G

Are the cylinder base seals in this engine radial o-rings (machined grooves in the casing) or plane seals?
If they are the former, I don't see how shimming would have any effect in the sealing (as mentioned in a previous post)!?

964TT

No they have the o-ring seal...

964TT

Engine is going to be done late January, with the shims. Talked with the engine builder and he convinced me easily. I have a lot of trust in his work, it will be fine.

In the meanwhile having some bodywork finished up, should be done in the next two weeks or so. More cooling in the front, for the intercooler and the oil coolers.

964TT

Carbon parts holding the oil coolers

964TT

I'm having some really wild ideas on how to finish up the car when the engine is completely under control and squared away. Just some last nip and tuck ideas I've been having lately, without messing up the Carrera 2 nb look.

Also found some nice 18" cup wheels (the Jara's). I thought they are cool because they are more in line with the Carrera 2 concept, but the downside is they are heavier than the modern Fuchs. I'd have to see how much but I think it's around 2-3kg per corner.

koenig_roland

who makes this stuff here in europe? fully cfk or just covered with?! :-)

964TT

These are full CFK, folded after the parts coming off a 993 GT2. The guy doing the bodywork on my car is great. When he had an original 993GT2 in a couple years back he made the molds, realising he could use that part some day.

Instead of having the coolers lengthwise they will be turned 90deg with these.