1999 Motor Swap

[jayburna688]

I have a 1999 Seville SlS does anyone know what engine can be swapped with my engine?

[Ranger]

I think you can use a '96 -'99 (SLS only)

[jayburna688]

I think you can use a '96 -'99 (SLS only)

So basically im stuck with a head gasket head bolt problemed engines. Im better off repairing mine.

[Cadillac Jim]

I believe that accessory mounts are fully compatible with 98-99. You can check for sure with one of the remanufacturers.

If it has head leakage, I would recommend that you keep your motor. There is a guy here, NothstarPerformance, who has his own machine shop and inserts. Or, you can use Timeserts yourself or have it done. My mechanic wouldn't take on a Timesert job because the local dealers hadn't had any luck with them, but some discreet comments a couple of years ago revealed that most techs did things like omit the template and hand-drill the tap holes and speed-drill in the taps, which is guaranteed to give you out-of-alignment, overheated, oversize threads for the Timeserts, and with 20 of them you are just about guaranteeing an early failure of at least one, quite possibly when you try to torque the head bolts. I don't know of anyone here who has done it themselves according to instructions from Timesert who has had a problem, though.

While your engine is out, you should consider replacing the oil pan gasket and the other gaskets that you can easily see, like the cam cover gaskets. Also, change the oil pressure sending unit on the oil filter adapter. If you are up to pulling the damper, replace the oil pump and, if you can, check the timing chain tensioners for wear.

If you do it yourself, keep it clean, really clean. When you put it together, consider one of those magnets that wrap around your oil filter to catch any iron dust that would go through the bypass when the engine is cold, and change the oil 500 miles after you get it going again.

I would also take the opportunity to service the transmission.

[Ranger]

Yes, repair yours and it will be better than new. Just be sure to Timesert http://www.timesert.com all 20 head bolt holes or use Jake's stud kit. http://www.northstarperformance.com

[jayburna688]

Does it matter if I can only find a sts engine will I be able to use it, and if so what would I have to do??

[Cadillac Jim]

The STS engine is in the minority. Depending on the model year and the part of the country you are in, the 300 VIN 9 cars make up as little as 5% of the Sevilles and Eldorados out there and usually not more than 20%. If you do find one and can't find a VIN Y engine, I think that the simplest thing to do, other than simply try it as-is, is to change the intake cams (and lifters) to those for VIN Y engines.

[Ranger]

DO NOT use an STS (VIN 9) engine in an SLS (VIN Y).

[dgaouette]

I was at the dealer yesterday and was talking to a mechanic regarding an engine he was just finishing up on. He replaced both head gaskets but no timeserts - none. He told me they only put in timeserts if aluminum comes out with the bolt. I think this is why some shops do not have good results. I strongly recommend - do them all, but who knows, he said they have been doing this for years and he is a dedicated caddy northstar mechanic????

[jayburna688]

The STS engine is in the minority. Depending on the model year and the part of the country you are in, the 300 VIN 9 cars make up as little as 5% of the Sevilles and Eldorados out there and usually not more than 20%. If you do find one and can't find a VIN Y engine, I think that the simplest thing to do, other than simply try it as-is, is to change the intake cams (and lifters) to those for VIN Y engines.

How are these engines so different are the accessories in different spots. My instructor told me it could just be a matter of flashin the cpu for a sts because the sts has different shift points and gear ratio's. I stilll have my sls heads couldn't I just swap them whole.

[Cadillac Jim]

The 1995 model year and later have PCMs that can be programmed by the dealer, and there are aftermarket programs that let you do most of what the dealer can do through a laptop or other PC, but you can't just "flash the CPU." Changes related to safety or security, or that may have liability implications such as removing the governor for 125 mph, are closely kept by GM and some dealers don't even have the wherewithal to change them. If you reprogram the PCM from scratch to expect a VIN 9 engine, it isn't just the engine that it expects to be changed. The suspension is not the same, either, and standard features such as speed-sensitive steering may or may not be there or be the same.

If you swap heads, you need to Timesert all 20 head bolts. You would be better advised do this with your existing engine.

For a 10-year-old car, it would be cheaper and simpler to sell your SLS and get a 1999 STS if you want an STS. A typical price for a 1999 STS with 100,000 miles on it right now is about $6100, private party sale, while a 1999 SLS with 100,000 miles on it can typically be had for $4900, according to kbb.com for cars in good condition -- which means a good engine as well as the rest of the car. The price difference is about $1200, which is about the cost of labor for R&R of a Northstar engine. Without a good engine, a 10-year-old car is worth very little.

As for the accessory mounts, I don't know, but rebuilders and remanufacturers sell the 1993-1994, 1995-1997, and 1998-1999 Northstar engines as separate part numbers. Since the engines are the same internally from 1995-1999, the only change for 1998 would be in the accessory mounts or motor mounts; I don't know the details. According to my 1997 FSM, the only internal parts difference between the VIN Y and VIN 9 engines is the intake camshafts. I haven't looked at things like the exhaust manifolds and crossover, but I've never heard that they are different. See Ranger's post #9; Ranger is very knowledgeable and experienced, and he says not to use a VIN 9 engine in a VIN Y car. Making it work would likely be more expensive than fixing your motor or putting in an used engine and trading it on an STS.

We've had several threads here started by people who buy a 10+ year old Cadillac and start trying to solve problems by bypassing and changing sensors and mix-and-match stuff. This type of thing causes snowballing problems in a car that can't turn off the MIL light and thus can't pass emissions testing in any state, at best. The only success I've seen there is going to a passive suspension to save money on the struts, and I'm uncomfortable with that on my car.

You will not have any trouble finding a used VIN Y engine from the 1998 or 1999 model years if you look over a wide enough area, such as statewide. There are people here that know of auto recyclers that will ship you an engine if you can't find one on the phone this afternoon. My advice is to get your gar in good condition as an SLS first, then look at your options; if you want an STS, simply trade.

[Cadillac Jim]

I was at the dealer yesterday and was talking to a mechanic regarding an engine he was just finishing up on. He replaced both head gaskets but no timeserts - none. He told me they only put in timeserts if aluminum comes out with the bolt. I think this is why some shops do not have good results. I strongly recommend - do them all, but who knows, he said they have been doing this for years and he is a dedicated caddy northstar mechanic????

[Ranger]

I was at the dealer yesterday and was talking to a mechanic regarding an engine he was just finishing up on. He replaced both head gaskets but no timeserts - none. He told me they only put in timeserts if aluminum comes out with the bolt. I think this is why some shops do not have good results. I strongly recommend - do them all, but who knows, he said they have been doing this for years and he is a dedicated caddy northstar mechanic????

I know that is how GM treats them on a warranty job. It's like playing Russian Roulette.