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Why would you ever want to voluntarily give up 25hp? Is this for the STS? I suppose it could be done, if the engine was from a 1998-1999 SLS. That's like swapping an LS1, for an LT1. It's theoretically possible, but has absolutely no point. I's just curious as to what reason you would want to replace a 300hp engine with a 275hp one. The only problem, is that the engine, and transmission are not going to get along very well. The STS transmision is set up for the power band of the L37 (vin 9) engine, and will probably not shift correctly, if used with the LD8 (vin Y).

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Actually, I think that swap would be very effective. The VIN Y engine has more torque below 5000 rpm than the VIN 9 engine does, it has more power below about 4500 rpm than the VIN 9 engine does, and it would work great with the 3.71 transaxle. Witness the Bonneville GXP, which uses the LD8 engine (VIN Y) with the 3.71 transaxle. You get the benefit of the shorter transaxle with the benefit of the better midrange power of the LD8 engine. It'd be a great swap.


As far as technical difficulties, you probably WILL have to find some way to get the PCM reprogrammed. They're probably sufficiently different to require reprogramming, even if the engine is the only thing that's changing. Perhaps Bbobynski has some insight on this.

It's the OTHER WAY that you can't go. You can't put a L37 engine where an LD8 engine once was. The L37 engine does not make enough low and midrange power to overcome the taller 3.11 transaxle, and you'd really slow the car down.

Jason(2001 STS, White Diamond)

"When you turn your car on...does it return the favor?"

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