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Old 10-29-2007, 12:13 AM   #1
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Default LG3 top swap to supercharged S1?

A friend of mine has an 86 Oldsmobile 98 Regency, and it has about 92K miles on it. He'd like to do an engine swap to a supercharged S2 L67, but something interesting has come up.

Someone mentioned that because the LN3 uses OBD1 and so does the 92-93 supercharged 3800, one could do a heads, manifolds, valve covers, supercharger, and injector swap, among maybe a couple other things. Would this work? I think the blocks are the same, and if so, wouldn't a top swap be technically feasible? If it really is, how would the transmission deal with it? I'd recommend at least a smaller pulley on something and a larger pulley on the supercharger for less stress on everything. How possible is this?

Also, can the S1 top switch to S2 valve covers?
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Old 10-29-2007, 12:21 AM   #2
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Either way, there would be wiring to add for the BCS and you'd need the PCM to properly control everything. A full swap with engine/tranny/PCM would be your best bet, with the Series II having the better starting point.

Yes, the the top end from a Series I L67 should bolt up. I don't know what the compression ratio is on the 86, though, and might cause havoc on KR. That and that bottom end isn't built as strong as the L67. And you'd be dealing with proper fueling and potential BOOM from lack of BCS control if you don't do a wiring/PCM swap.

The transmission might last a little while, but it definatly wasn't designed with the L67s low end torque in mind.

L36 valve covers are the same as earlier models, I believe. The S2 valve covers have reliefs for injectors.
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Old 10-29-2007, 12:31 AM   #3
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BCS? Body Cavity Search? Bangladesh Civil Service?

This is a really cool reply. I thought this would go slow, but it seems this is pretty much covered. In a perfect world, how much work would have to be done? Can this be reduced to man hours? In a non-perfect world, could this be done, tested, not liked, and reversed?
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Old 10-29-2007, 12:37 AM   #4
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BCS - Boost Control Solenoid - PCM controlled device that dumps boost in times of engine trouble - occasionally saves the bacon.

Full swap? A week if you know what you are doing. Top end swap? A couple days. Then add in time for wiring. And remember to get an EPROM burnt for the particular combo.

It can be reversed, but it would be a pain in the *** to swap an engine back in. Although, Boosty is pretty good at engine musical chairs.
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Old 10-29-2007, 01:11 AM   #5
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"Engine musical chairs" is a really cool way to put it.

How accurate is the assumption that this is made easy because of similar transmissions? I think they're at least similar because they run off of vacuum lines whereas the 4T65s are mostly electronic.

If the top end swap is done, it'* just a bunch of gaskets, the heads, LIM, UIM, valve covers, supercharger, and fuel injectors? Possibly the fuel pump would need to be replaced, but are the cars different enough to require tinkering with the gas gauge? I'm aware that the S1 and S2 share the same fuel gauge ohms, but how about the 86 LN3?

I think past this, the first step to it all, should we happen to do this truly, is to get the service manuals for the two engines we're going to be tearing apart. But! What about the 92-93 supercharged engine? If it'* still good, can it get all the LN3 goods without as much of a hassle?
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Old 10-29-2007, 03:30 AM   #6
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The bottom end wasn't designed and built for it.
The transmission in the car wasn't designed or built for it.

Will it work? Maybe. For how long?

That'* the question that also dictates 'how much will it cost to make it last?'
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Old 10-29-2007, 03:38 AM   #7
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If we can find a 4T60E-HD, we'll try to put it in, but I see nothing wrong with turning the LN3'* transmission into pudding for the time being. It'* not my car, though...

If a 4T60E-HD goes in, is there much else to keep LN3-tuned? I think it would be almost a supercharged S1 swap, right? If the LN3 doesn't deal with it, we may be the first to let you guys know.
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Old 10-29-2007, 03:10 PM   #8
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The 86 is not an LN3...

This would be the LG3..... But the Question is weather or not its the Vin 3 or Vin B..

Either way both of these engines should be 8.5 : 1 compression.. But the question becomes will the L27-67 Heads even fit the LG3?

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Old 10-29-2007, 03:15 PM   #9
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Well, I found a pic of your friend'* car you posted.

Name:  P1010720.jpg
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Answer is no. The engine he has is the Pre "3800" called the 3.8 SFI (RPO LG3). If I am not mistaken, the block is different, and will not allow the 3800 heads to bolt to it, as coolant and oil passages are in different places. Plus the LG3 isn't the strongest engine in the world. I have seen alot of them kill the timing gears, and eat bottom ends. :(
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Old 10-29-2007, 03:18 PM   #10
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Wow. How much of the VIN do you need? What are the differences between the LG3 and the LN3?

I kind of feel bad, though, since the engine idles very smoothly and has no kinks or anything. It looks steady as when off when idling, and the acceleration feels really smooth. Is this sacrificed regardless of the top end swap job quality? I can't imagine superchargers hinder smooth idles, not even in cases like this.
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