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Supermag05
Joined: 08 Jan 2013
Posts: 2
Location: Tennessee
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 Posted: Thu Jan 10, 2013 6:31 am Post subject: 87 o 81 engine swap question |
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Hello, I am new to this forum and hope someone can answer a question for me . I have a 88 924s with the 2.5 motor. It has a rough interior and bad transaxle. I can get a near perfect 81 924 with the vw engine that has a knocking rod. My 88 motor runs great with 88k orig miles. How difficult is it to transplant the 88 motor into the 81 body? Is it worth it, or would it be cheaper to rebuild the vw motor. I really would like the power of the 2.5. Any help would be greatly appreciated.
Thanks
Scott
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fiat22turbo
Joined: 18 Jan 2006
Posts: 4040
Location: Portland, OR
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| Posted: Thu Jan 10, 2013 8:59 am Post subject: |
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A number of parts will interchange.
However the motor mounts and crossmembers are different between the two and require cutting and welding to make it work.
I'd probably just swap the good interior bits from the 81 over to the 88 along with the transaxle. Anything else you need, you can scrounge up from an early (85.5 and earlier) 944 or another 924/924S
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Stefan
1979 924 Carrera GTS (clone-ish)
1988 944 Turbo S (Silver Rose) |
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Supermag05
Joined: 08 Jan 2013
Posts: 2
Location: Tennessee
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| Posted: Thu Jan 10, 2013 11:07 am Post subject: Motor swap |
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I would but the 81 I just got is 1 of only 400 weissach editions this mint. A rod knock is the only. Problem. In the future I think this limited edition will be worth more than my plain 88.
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Supermag |
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ideola
Joined: 01 Oct 2004
Posts: 15550
Location: Spring Lake MI
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| Posted: Thu Jan 10, 2013 1:32 pm Post subject: Re: Motor swap |
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| Supermag05 wrote: | | In the future I think this limited edition will be worth more than my plain 88. |
I seriously doubt that, and even if it were the case, modifying it the way you are talking about would destroy any chance of it "being worth something" in the future. The ONLY collectible 924s that are worth anything are completely original, unmodified examples. What you are contemplating would destroy any chance for the 924 to retain value, assuming it has any to begin with.
That said, the 2.5L into an early chassis is NOT an easy conversion. The 2.0L engine sits on brackets that are welded at the rear of the engine bay. These would have to be removed in order to fit the 2.5L motor.
In addition, the 2.5L motor sits on an aluminum cross member, which mounts to the frame spar in completely different way than the 2.0L cross member. There is no easy way to convert the cross member mounting points. Probably the best way is to find a skilled welder who could section in the frame spar containing the mounting points from the 924S into the 924. See comment above about destroying the value of the 924.
Now, if you are able to solve that problem, you have a host of other considerations. First and foremost is the wiring and electronics. This is no splice and dice operation. Your best bet would be to swap in the entire 2.5L wiring harness, which you would need not only for the Motronic DME, but also for the speedo and tach.
| fiat22turbo wrote: | | I'd probably just swap the good interior bits from the 81 over to the 88 along with the transaxle. Anything else you need, you can scrounge up from an early (85.5 and earlier) 944 or another 924/924S |
Swapping interior bits is no big deal, but the transmissions are NOT directly swappable, in either direction, because the 81 uses a 19mm input shaft while the 924S uses a 25mm input shaft, each with a correspondingly sized driveshaft (i.e. torque tube).
You've already stated that the trans in the 924S is bad. You might be able to run a 2.0L clutch disc in the 2.5L arrangement, but the pilot bearing would be wrong, so you'd have to come up with a custom solution there. On top of that, the gearing in the 81 trans would be completely wrong for the higher output 2.5L motor, and that clutch would probably slip. So you would be better off swapping in the torque tube from the 924S, and then finding a used 924S or 944 gearbox to replace the bad one. Swapping the trans isn't that bad, but swapping the torque tube means dropping the torsion carrier from BOTH cars, which can be a bear of a job. If the big-a$$ bolts that attach the torsion carrier to the chassis have corroded and fused to the aluminum insert in the bushing, you have to cut them out, which is very difficult to do even with a sawzall because there is not much space to get the saw blade on the bolt. Ask me how I know.
This can all be done, but man is it a lot of work, and for what?
If you really think the 81 is worth something, and if the only problem is truly just the rod knock, why not just fix the rod knock? It's probably just in need of a mild rebuild of the short block, which would be WAY much less effort and cost than doing the swap.
If you need a new trans for your 924S, I have one that I pulled from an 87 924S. It's already crated and ready to ship. $150 for the trans and probably as much to ship it.
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924 FAQ (Technical)
