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944 engine in an early 924

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Joined: 25 Mar 2009
Posts: 69
Location: Walnut Creek, CA

PostPosted: Tue Feb 10, 2015 5:13 pm    Post subject: 944 engine in an early 924 Reply with quote

Hi team,
I've read through a number of posts on this forum on 924 engine swaps and wanted to run the following by this group to make sure I have an accurate picture of what would be involved in a 944 engine transplant for our race car.
Car is a 1979 924 with some 944 bits already transplanted: namely, front struts and spindles, brake system (discs, calipers, 944 booster and perhaps the brake MC...), radiator, body panels, and also a GM alternator

The car has been getting much more reliable for LeMons racing.... after some teething issues essentially replacing everything on the car over the past few years. At this point, fuel system's solid, ignition solid, handling is great and the brakes are perfect. We have had, however persistent problems with our snailshell tranny. We've gone through 3 or 4 at this point. We have the shift bushings in good shape, but racing is hard and we keep replacing these units with used, already worn synchro replacements, so lifespan is short. We also now have had a second issue with cracked tappets - we had an oil feed issue a little while back (clogged pickup tube) and occasional overrevving (due to tranny troubles). We've got some spares that will get our engine back online..but we've resurrected discussion of an engine swap. As LeMons has become more mature, we continue to be outclassed in HP at the track, and if our drivetrain is proving to be a persistent weak point maybe we just get ourselves a little more power while we're at it

We're thinking of moving to a 2.5L 944 powerplant and I wanted to see if the following would get us from pt A to pt B.
1) Obtain a 83 - 85.5 donor car with good drivetrain
2) Pull the engine and refresh timing belt, rod bearings, oil pan gasket. Fab up windage tray. Check/replace clutch
3) Reinforce 924 steel crossmember and chassis mounting points and fab up motor mounts for crossmember
4) swap in 944 clutch master, connect up to existing brake master and swap over 944 clutch pedal, making sure to mount securely
5) rear torsion carrier - slice off the snailshell mounting ears and mount new tranny. (I think there are chassis points to already accept the 944 tranny). Use 924 or 944 half-shafts? Keep steel trailing arms or go alum?
6) Mount GM alternator on engine if possible (this things been much better than the stock 924 unit and its cheap)
7) Install 944 torque tube and engine. Prefer to keep our 924 front sway bar - not a huge fan of the 944 system, but perhaps there will be clearance issues?
Make sure our radiator clears
9) Swap over DME and 944 electronics. (944 coil? how much of ignition system do we need to bring over? all?)
10) Keep 924 fuel pump and manual steering rack
11) Refab exhaust
12) Redo alignment and ride height, check balance - probably added just as much weight in front and rear? If not adjust shocks / sway bar diameters

Is that a fair laundry list? advice? ideas?
Its a team car, so we have a handful of workers. Our chief wrencher is a bus mechanic and 911 owner, we've got one guy pretty good at fabrication, one electrical nerd, I'm suspension and we've got access to a full shop and most cool tools except a plasma cutter. And a couple of us have 944 track cars as well that we wisely keep away from the shop, lest they be cannibalized.

1989 944 S2
1979 924
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Joined: 26 Mar 2013
Posts: 873
Location: Central Georgia

PostPosted: Tue Feb 10, 2015 6:41 pm    Post subject: Reply with quote

Buy a 924s.
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Joined: 27 Aug 2004
Posts: 2122
Location: Sweden

PostPosted: Tue Feb 10, 2015 6:51 pm    Post subject: Reply with quote

I dont know how many races youve gone through, but it seems like there need to be some serious gear change training needed. I ran a 924 on track for years with worn syncros(2nd), but it didnt get worse. But I had to quickly learn how to do heal toe downshift fluently, that had other improvments on the track driving aswell since it calms down the car during braking.

You seem to be good at fabricating stuff, so I would mostly be concerned about the electronics, cut as much of the loom as you can from the donor car. If you can take the whole box of realys and stuff it will probably makes things easier.

Wouldnt expect the 944 engine to be more reliable, but the power will be nice.

I raced with a endurance team that took a 76 924 out of a barn and endurance raced it. Engine worked flawless for many races, didnt event consume that much oil. It had being sat for years. Fun car, but needed a 5th gear
1980 924 Turbo
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Joined: 25 Mar 2009
Posts: 69
Location: Walnut Creek, CA

PostPosted: Wed Feb 11, 2015 2:05 am    Post subject: Reply with quote

Thanks Cedric. Car's been through a dozen or so races in the last 6 years. Engine was originally our strong point. Crank pulley pin sheared our first race, but after that no trouble at all until we found previous owner RTV "gummy bears" clogging the oil pickup. After that we've had some top end issues.
I've been wary of the 2.5 - I know its rod bearing reputation and am not expecting overall reliability improvement of the 2.0 litre.
Re: transmission - we lost the first one due to shifter bushings before we read up and wised up on that. We do rev matching and even double-clutching when we can, but races are grueling (we did one full 24 hours) and these replacement units are a little grindy even when we swap in a new one.
1989 944 S2
1979 924
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