Porsche Enthusiasts Club Forum

Very good numbers already!

A pic of the bhp/torque graph

Here you go Jon, you wanted to see how these Omega pistons were coping after a few thousand miles and their burn patterns. Ideally it would have been under better circumstances, however I found coolant in cylinder 1 and 3 last night! I suspected the HG was failing a few weeks ago when the coolant was becoming pressurised. The last few days saw cold starting on 3 cylinders until revved and warmed for 30 secs or so.

So I started at about 2.30pm this afternoon and had the head on the floor before 7pm tonight

The bay


The head


The gasket - note the copper oil gasket deformation, no idea if this occured during the head coming off, unlikely!?


No 1 piston


No 2 piston


No 3 piston


No 4 piston


No 1 valves


No 2 valves


No 3 valves


No 4 valves


One thing of concern was that despite being re torqued after 200 miles, there was a mix of torques in removing the head stud nuts and the studs themselves, some being very loose versus the tightest. Going to use Steve Bassingtons theory of light equal torque of the studs prior to the nuts. Treat them all the same this time.

I have a new OEM Porsche/Victor Reinz head gasket and cam belt arriving at Bristol OPC tomorrow. Unfortunately its my daughters 2nd birthday tomorrow and I'm not even going to ask to put it all back together once she's opened her presents! Going to try and get it all done on Saturday and be driving again Sunday!!

Disappointed to see this Steve. I hope that a new gasket will fix it.

So I believe the failure to be a few central ARP studs decided to relieve themselves of their clamping force duties. Whilst driving under normal circumstances this didn't cause any issues, once up to higher speeds and full boost this was causing some compression/boost pressure to slightly lift the head from the block. Hence some overheating and then later water seeping back into a couple of bores when left to cool.

So this time I torqued the studs in at 15ftlbs and then the nuts in at 90ftlbs paying particular attention to the central studs/nuts. A new OEM Goetze headgasket was bought to replace the previous Victor Reinz. The Goetze appears to be a touch thicker and 'tackier' than I remember of the VR. New Dayco cam belt as I had issues with the Contitech being a touch too long despite having the right number of teeth. And finally a new 944 all ally radiator with 56mm core. All went back together quite easily and quickly over the previous two evenings with last night being the start up. Took a while to get started as I think it wasn't receiving full fuel pressure. Starts and idles spot on and no oil or water leaks. Runs a lot cooler with the new radiator. Done 10-15 miles on it already.

Now I'm considering parking it up until Gaydon so I don't break it again!!

I look forward to seeing it there.

How are the strut top mounts going? I keep seeing them on evil-bay and am tempted with a set.

All good so far. Appear to the worth the small outlay. A bit more noise coming through the chassis maybe but I have stripped out so much insulation I can't be sure.

Good news. How many miles have you done and do the bearing look like they can be replaced easily?

3000 miles in 3 months. Didn't take any notice of the bearings prior to fitting.

Wereyou getting them anodised? How did they turn out and what did it cost, please?

I didn't bother in the end. I coated the some of the mating surfaces with Duralac to avoid mixed metal corrosion but left the rest bare ally.

Now here's an interesting video from Mittelmotor and their 924 Carrera GT on Nurburgring showing data logging details. Quoted elsewhere to be achieving 310bhp due to GTS spec but here showing boost at 1.3 bar.



Flat out at 160mph on the rev limiter @ 6700rpm!

Don't normally go for fuel additives (occasionally use an octane booster) but stuffed some Redex into a full tank of Momentum99 today more for the fuel system cleansing ability than performance enhancement (Fifth Gear alleged a 5bhp enhancement was seen after one tank full of use to 'clean' the fuel system on back to back dyno session with a VW Corrado this week) as I had a slight hesitancy on the throttle when coming off and on when cruising, boosted it up to a min 0.9bar, and went for a drive ............. whooohooo!!!! Super quick, the butt dyno suggests if 210ish/231 torques is available at 0.7bar then 0.9bar has to be somewhere circa 230-240ish bhp and 250ish torques, it really is a marked difference in how the car pulls circa 3000-3500 when boost is full on, the car squats at the rear and the drive train is taking a real hammering, the engine is pulling hard and revving up to 5500rpm cleanly with no knock warnings, happy days, will probably blow up or chew its again HG soon.....

Still has its coolant pressurising issue despite the new 951 ally rad and that the overall cooling system runs far lower temps which could be a warped or porous head. When I shut down from a hot drive I need to bleed the system at the top of the thermostat housing release the pressure to avoid coolant being pushed out of the header tank. A bit of a pain. I did have a vent line off the top of the thermostat housing venting into the header tank but this didn't help. However its been also pointed out I could have localised engine hotspot(s) causing boiling/cavitation and that a swirl pot would help in the system. Used in many modified/race engines, I am now searching many t'internet pages to glean some info. Anyone shed any light on use of a swirl pot and if this would be of help in my car?

Anyway heres another shot of the engine so you can see I haven't got a lot of options in fitting a swirl pot into a high spot in the system

Id expect a 'swirl pot' to be a small intermediate tank alongside the fuel tank, used to prevent fuel starvation during hard cornering and such...?

Correct, but also used widely in cooling systems to remove air caused by boiling and cavitation due to localised hotspots within the engine. I have located a Sierra/Escort Cosworth in line swirl pot which I should be able to fit between the thermostat housing outlet and the radiator.