Porsche Enthusiasts Club Forum

Hello all. To introduce myself: Dave Overington. Australia. Recently retired. Have two 928's, a 914, two 944's (one NA, one Turbo), a 968 and recently purchased a much-neglected 1982 924T (an ex UK car - registration number etched on all windows).

This post is about my 924T. The car is just back from the paint shop, looking fantastic in its original Saturn Metallic colour. I've redone the carpet. Added 8" rear and 7" front et 52.3 D90 16" wheels. New tyres and new konis yet to come - along with possibly better front calipers (ex RX7 or Volvo 240 ventilated disc or suchlike).

I have also purchased a used 924T engine (my matching numbers engine can be stored away safely in case these cars increase in value). The 924T engine I have bought has already been modified and produces 250 rwhp. Running Haltech ecu (older version, - platinum sport 1000), garret turbo mounted in front of the cam cover (certainly easy to access), air / water intercooler, highly modified inlet manifold / plenum etc. When I bought this engine I bought it knowing that it smoked and probably required a complete rebuild. The price reflected that fact.

So now I am turning my attention to rebuild components. This car will be a street legal track car for 'gentlemanly' track days. No racing (ha ha!. Not half).

So, given that the new engine will in all likelihood require a rebore (engine has never been opened so is still 86.5mm) and will need new pistons, my thoughts are along the following lines:

1. Use a set of new Mitsubishi forged 4G63 conrods. These are for a 45mm big end journal (cf 47.95) are 150mm long (cf 140.4), have a gudgeon size of 21mm (cf 22?/24?) and are very very marginally too wide at the big end journal so will need a very small amount taken off each side to fit the 924T 27.9mm crank journal width.
2. Offset grind the crank by 2.95mm to give 2.95mm increase in stroke
3. Have pistons made with the required gudgeon size and compression height to suit. A very reputable company here in Oz can do this for me at a very competitive price. My preliminary maths suggests that with the required compression height I will have 26.55mm from top of gudgeon to top of piston to fit in the 2 compression rings and one oil control ring. Rod : stroke ratio will be 1.72.
4. Compression ratio to be determined. In the order of 9:1 (more?? less??)
5. Boost? A modest number, whatever that is, to safely give 250-275 rwhp.

I also intend to run an electric water pump - the way the amended belts run currently I do not have enough crank belt wrap to feel comfortable. By using an electric water pump I will overcome this concern.

I already have on my shelf a 944T (951) radiator and will be using that - with a pair of fans and suitable fan shroud.
I also intend to run an electric booster pump for turbo cooling, a la 944.
Re cylinder No.4 cooling concerns, my plan is to open up that rear fitting and associated coolant plumbing to c. 30mm and disconnect the cabin heater from that circuit.
For cabin heating I am considering a separate radiator to heater core to radiator circuit, with a user-controlled electric booster pump for circulation.
And I also have on my shelf an OEM 944T intercooler and want to use that instead of the air / water system that I have inherited with this engine. Of course, having just had all the panel and paint work done I am loathe to start 'hacking' away at parts that are visible in order to fit the intercooler. I am pondering if, once my current engine is removed and before I install the rebuilt engine, I will have enough room in the engine bay (radiators out of course) to make the required mods from within the engine bay to fit the intercooler without disturbing my lovely new paint job. (I am however inclined to doing 'something' in the front bumper to provide intercooler fresh air ingress, much like the 944T - but have yet to fully consider the air routing from such a slit to the intercooler, and how best to maximise the volume of the void between slit and intercooler so as to slow air flow speed and reduce turbulence). I guess another intercooler cooling option might be water mist, controlled by the ecu when ever inlet air temp exceeds xyz degrees?

Anyway, that's enough for a 1st post!

I would welcome any comments on the merits or otherwise of what I propose doing.

Best regards

David

Welcome Dave!

That's a fine car collection and sounds like you are well on the way to resurrecting your new 924.

I recently had my 944T engine rebuilt, but stuck to mostly stock stuff with a few nice upgrades. Sleeved bores with bespoke JE pistons. Got the head tapped for a steam vent kit at the bulkhead end, and got my oil pick up pipe strengthened, loads of other things but didn't deviate from stock much unless forced to. The full build thread is on PCGB forum.

https://www.porscheclubgb.com/forum/tm.aspx?m=1099791

It was a big learning curve for me but I'm still some way off being able to advise on any of your questions, good luck though!

Stuart

Hi David , looking forward to following this .

Not seen the 4G63 used in the 924 before . I am using them in my 944 with 94mm offset crank . Nice sturdy rod .

I have also used rods from PPM based in Oz before .

Some pictures would be great .

Simon