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Discussion Starter #1
Hey guys, I came across an engine today to replace the cracked block in my car. The only problem is that it came out of a 2001 sts, and my car is a 99. What is involved in converting it to work? It looks to be very close, however there is an air pump and lines and the coils are inside of the valve covers instead of the back. Can i use the old distributer/coils and what not, so that all wiring is the same or are there differences? Has anyone successfully done this job?
 

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94 ETC,97 STS
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Someone did this swap a couple of years ago. It was not easy and they fabricated a lot.

They did not give many details and only gave one post to say they got it to run but it wasn't easy.

If you are a good fabricator and have extra time it might work but you'd be better off getting the correct engine.

The blocks do have differences in them. You can't just strip the engines down and swap blocks.
 

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'03 STS (RIP), '89 Eldorado, '13 Malibu, '89 Grand Wagoneer
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not to mention an SLS and STS has a different northstar
I'm not sure that would have any bearing assuming they were of similar model years. I know of at least one guy who put the engine from an SLS into his STS. There are also quite a few people who feel that the combination of the LD8 and the STSs drive ratios make for the perfect compliment to each other.

Whether it's easy or hard to do I have no idea as I refuse to do any sort of real work on a car with a computer more powerful than the Apollo spacecraft... hell if it doesn't have a carb I usually won't touch it, but I digress...

Now... if you want to replace a 360 with a 258 or vice-versa then come talk to me.
 

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There were some major changes in the engine between those years.
The main thing is the coolant crossover, throttle body, and idle control systems are different.
There are differences in the motor mounts too.
I'd try to avoid it, look for another engine closer to the same year.
 

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Discussion Starter #6
Okay thanks guys, just thought that I could drop the old one out and lift the whole new assembly (transmission, motor and subframe from a 2001) into place but I figured the electrical would cause a problem.
 

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Discussion Starter #7
By the way the 99 is an sts, which is the seville, not an sls with the smaller motor. My car has the 4.6 H.O. Northstar, not sure what the differences are but there must be some.
 

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Okay thanks guys, just thought that I could drop the old one out and lift the whole new assembly (transmission, motor and subframe from a 2001) into place but I figured the electrical would cause a problem.
By the way the 99 is an sts, which is the seville, not an sls with the smaller motor. My car has the 4.6 H.O. Northstar, not sure what the differences are but there must be some.
I know I'll be summarily corrected if I'm wrong, but I'm pretty sure your best bet would be to find an engine from a '97-'99 Seville. Whether one from an SLS from those years would be an *relatively* easy swap in I would defer to ewill, aj, or ranger.
 
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