I know and I've read the sticky notes on swaps and interchangeable parts. However, I'm stuck on something. I have a '97 SL1, which is burning oil from a blown piston ring. I'm talking like 2 in 500 miles bad. I have access to a '02 SC1, and am wondering something. I know the SC1 has the new wiring, with the BCM and all the stuff, so I'm assuming I can't put the whole engine in the old car without doing a bunch of rewiring. However, since it's my pistons rings goin bad, I about if I'd run into any complication on just swapping the blocks. I know it says they're completely interchangeable, but I know the newer cars have different rods and pistons and such.

I know it might be easier to just tear down the engine and change the rings, but I don't know if there's any more damage on the '97. Just let me know if I'd have any trouble taking the newer block, and putting it onto the older head. Thanks to anyone who responds.

 

Apologies.
I thought I posted my response to this but apparently not.

Although the blocks are interchangeable, as you pointed out, the internals are different.

I know they changed the intake manifold and I'm pretty sure the intake and exhaust manifold bolt patterns are different as well. If it's a plastic intake on the newer engine, It has a design flaw and you don't want it. 3rd gen also has The vertical throttle body so you'd have to keep your 97

Since the cams and crank are also different in the later head and block, it's not clear to me If the timing chain and all items timing related would still be exactly the same. Not saying it wouldn't, just saying I don't know. I suppose you could check part numbers for the cam sprockets and the crank sprocket and the chain.

I'm going to guess that the ECM for the third generation vehicle is significantly different than that for the 97. Not just based on the presence of the BCM also be added to the system but the nature of the new configuration of internals is handled. Meaning 97 PCM Is programmed to not look for a BCM, But more importantly it knows what input from what sensors are acceptable. This may not be the same calibration so to speak on the third gen ECM.

So if you took the third generation ECM and tried to use that in the 97, I don't think the vehicle would ever start because the ECM is waiting for the okay from the BCM to enable the fuel injectors based on passlock II, which 97 does not have. So you would have to use a 97 PCM.

Usually, people are trying to swap an entire third gen engine into a second gen vehicle. Besides the BCM issue and security issue, that's doable but a huge pain in the ***. I can't say for sure if this will work, but I would shy away from doing so and if you have the means to rebuild the 97, I would go that route. Might as well refresh the head while you're at it.

 

So it probably wouldn't be a direct bolt up, but probably finding the correct parts to combine the two. I've spent a lot of time reading forums, and I believe I have an idea. The SC engine only has 59 miles on it, it was donated to a school I have ties to, and they're giving me permission to take what I need from it. Would it be possible to just swap the entire engine over to my car? I know the wiring is different, but I read that you should be able to swap out all the sensors on the new engine, with the old sensors from my engine so that the wiring works correctly. That is, of course, a theory, and would like your opinion.

 

A full transplant.

Do you live in a state that requires emissions inspections? This is a vital aspect, because ultimately you will probably not be able to get rid of every last p code when all is said and done. If you have a p code lighting up the SES, in most states that is an immediate fail.

Assuming you don't live in one of those states.

1) usually when you do a full transplant, you also take the ECM with to manage the engine. And in this case the BCM.

But which one can actually run the vehicle?
If you use the '97 PCM, you can ignore hooking up additional things like the smog pump, anything that has to do with the pre cat (which I believe is integral to the exhaust manifold but I may be wrong about that. So you'd have to take that with too, It would have to bolt on.), and any other sensors that the 97 doesn't have. Taking this route, the 97 is only looking for what should be there in a 97, the BCM is now irrelevant, And so is passlock security. All the interior options should function normally.


You keep all the sensors you have and find them their homes on the newer engine. Some will simply have to be purchased because they are not identical between the engines. Can't tell you which ones off the top of my head.

But how will it drive?
The two biggest things that affect drivability in the s car are the ECTS and the front O2 sensor. They combine to manage the air fuel mix in real time. Since it is MPFI, the ratios controlled by pulse length to the injectors.

I'm pretty sure the ECTS was universal from 91 to 02. However, with the precat, I do not know if the same front O2 sensor is used nor if the response curve is the same as the front O2 in the '97.
This is going to come into play with the fuel mixture adjustment. The response curve in the 97 PCM will be followed, but it may not correspond to the O2 level output of the newer engine. This may cause it to run lean or rich. Not the end of the world, but if too lean or too rich it probably won't drive properly and if too lean you run the risk of burning valves. If too far off, that will throw a p code.

Third gen ECM

Taking this route creates the nightmare of integrating not just the ECM but also the BCM of the newer engine into the 97. Also, remember that in '97, the PCM controls everything in the car except the transmission. Both engine and interior.

Third generation s cars got a BCM which then offloaded most of the non-engine management stuff from the ECM to the BCM. You'd be better off taking the entire vehicle harness from the third gen s car and rewiring the whole damn thing on the 97 if you try to go this route. Pretty much the only way to get everything connected properly. Plus for security, you'd need to swap out the ignition switch for one that has a passlock sensor.

You can't flash a third gen BCM to behave like it would in a second gen s car because second gen s cars didn't have BCMs, so it is literally impossible. It would have to live as a third gen BCM, which is fine. The issue is What options is the BCM programmed to control vs The options on the 97, and is the logic in the BCM equivalent enough to the logic that was used to control all of them interior body stuff in '97 that was controlled by the PCM.

This entire thread highlights the potential issues that arise when you try to swap engines between different generations of s cars.

Please know that 99.8% of my experience with s cars is with the DOHC not the SOHC, but the issues discussed here are identical.

Take your time going through the minutia that I haven't even mentioned because I haven't thought about this in a long time. You don't want to start ripping wiring harnesses out etc and get caught in no man's land or build a car that will never run.

Please keep us informed as to which path you take if either or if you do a rebuild on the existing engine.

Thank you for making me think about this stuff harder than I have in a long time.

 

I agree, if the late engine is complete, all the early sensors physically fit and you can attach the exhaust it will work. I installed several JDM take out engines in the 90s. Since the basic engine was the same as what they sold here, I would strip to a long block and use all the US mandated equipment and sensors. Saved a lot of high mileage cars and trucks with low mileage engines. Take your time and have fun with your project.

 

Alright, I'm glad I got 2 sides of the situation. I'm also glad someone approved of the theory I had made for the sensors. Thank you both

 

Definitely run the computer system that came on the 97 and all the 97 sensors and wiring.