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Old 11-18-2007, 04:35 AM   #1
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Default Actually planning an LN3 to L67 top swap

Hello. I'm trying not to make this a double-post by disregarding the previous thread about the LG3 to some extent. Considering that there is an LN3 in an older Bonneville that needs to be supercharged, what is needed from a Series 1 engine to do this? The idea is to perform the top swap with the transmission'* life in mind, as weird as it may seem.

I would like to have the 92-93 supercharger because of the lack of coating and the smaller throttle body. This would also make it easier to get a 2.8" or larger pulley to make it shoot in less air. Hooray for transmission life! Will a 94/95'* supercharger pulley bring down the 92-93 supercharger much?

With the supercharger and throttle body swap probably comes the LIM and a set of heads and valve covers. Are the valve covers interchangeable between the engine types? Also, I believe larger injectors are in order, and so is perhaps a very thorough check of the fuel pump. Does anyone know off-hand what the PSI/bar of an LN3'* fuel pump is?

I see that the rear accessory brackets for these engines have the alternator and power steering pump locations quite different from each other. Is a rear accessory bracket swap in order as well? The harmonic balancer, AC compressor, water pump, and perhaps one more pulley seem to be in the right place.

I'd like to do a transmission fluid flush, change the filter, and check up on all the wiring of the transmission to see to it that it'* in its best shape for this swap. So as not to throw too much low-end torque to the transmission, I would like to open up the exhaust to a 3" or so before & afte the catalytic converter. The stock piping is already set up fo a single exhaust pipe that goes all the way back, and that'* just fine. I believe this would make it easier and cheaper to go to a 3" pipe because the heat shields and weld locations may stay the exact same.

What are some things to keep in mind, and what is most important to research? I know I'll look a lot into the PCM and such very extensively, but what is the best way, aside from getting all the parts and gaskets, to get started on this project?
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Old 11-18-2007, 07:27 PM   #2
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If i remember from f14crazys LN3 topswap he had to use 2 front valve covers. he didnt have to swap the heads. He had to use the harmonic balancer from the L67 but it had to be machined to fit the key way on the LN3 crank. he also had to use the accessory bracket from the L67. I think you will have to modify the powersteering lines to get the ps pump to go in the bracket. i dont believe you will need a new fuel pump. But you must check the fuel pressure to make sure that the pump you have in there is good enough. If it isnt than i would replace it with a good one from a L67. you can use the fuel injectors that come with the donor L67. You will need a custom burned chip Probably from Ryan at GMTuners.com or whatever they go by now. Ryan is the one who burned F14Crazy'* chip. When you have it all together you must scan for Knock. That is what i remember from his topswap. You are going to get alot of people to tell you to just swap the whole engine. Because in the long run it will last longer. The pistons and rods are stronger in the L67 and better suited to handle forced induction. But if you get you topswap tuned right then it should run fine for many more miles. Its clear your not going for horsepower. mostly just the cool factor of a supercharger. Have fun
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Old 11-18-2007, 07:32 PM   #3
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You will need the fuel pump. The Series 1 L67 pump is a higher-rated output unit compared to the L27 and earlier motors. Don't skimp on the fueling, or it will cost you a piston or six.

Swap the entire drivetrain. It'* easier and cheaper. It will also last longer. Many of the LN3 and LG3 (and L27) internals were not designed or intended for forced induction. This also includes your axles and transmission.
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Old 11-18-2007, 07:45 PM   #4
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I told you so. will is normally the first to say just swap everything. he knows what he is talking about though. That isnt what this thread is about it is about a topswap. I will assist him the best i can with the goals he has in mind.
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Old 11-18-2007, 10:15 PM   #5
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Hypothetically, if we're capitalist corporate fat cats who will run this into the ground, while taking proper care of it, it is technically possible, though, right? I kind of hate to admit it, but I'd much rather do an all-out Series 2 swap some time later. That would probably be the most effective way to go about it. As for now, however, we're probably going to run a 3" or slightly bigger pulley, if we can find it on eBay (for Mustangs, I believe), and we will open up the exhaust so that the car will sound like it'* about to ravage all those dear to you. As I'm aware, 3800s are emissions-friendly, so most of this should not be a problem.

Will, you are awesome and completely right. Please don't think I'm disregarding your advice outright. In fact, I couldn't agree more. This certain case, though, is weird because we just want to have a supercharged car, not a faster car because of an added supercharger. It may actually still be faster, though.

Is the LN3'* harmonic balancer bigger or smaller than the L67'*? I'm going to check on the following, but I'd like to ask here first if the accessory brackets have the same mounting holes and bolt sizes. I think since the blocks are reportedly the same, it shouldn't be a big deal. How do I contact Ryan at GMTuners? Is that Ryan Gick of Sinster Performance?
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Old 11-18-2007, 10:23 PM   #6
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Yes, that Ryan.

If you're absolutely determined to do this (and I wish you wouldn't just flush your time and money), use a Gen2 91-93 SC and TB ONLY. That'* assuming you can find a 3" or larger pulley. The Gen 3 on the 3" pulley will provide too much boost for you.

You need 5-6psi to be safe.

The harmonic balancers are the same diameter. Contact F14crazy or check his old topic for modification details.
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Old 11-18-2007, 10:49 PM   #7
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Flushing is a great way to put it at first glance. However, it'* a friend'* Bonneville we're modding to do this for fun rather than to make a racecar, and we're trying to do this so that it'* tuned well, has a Gen 2 supercharger, and runs smoothly. I think the LN3 has some pretty good pickup already, and the supercharger, if it helps, should only help just the tiniest bit. The car looks like it'* new, though it has some minor rust on the underside, and the suspension needs to be replaced. This is probably a good time to look into suspension parts that are far stronger than stock.

The other thing about this is that this is an LE Bonneville. It'* so bone-stock that there are map holders on the door panels, and the seats are firm cloth. It reminds me a lot of that Bonneville that was recently found on eBay for less than $300, except it has a full dash with tach and all. Same color & such, though not trashed inside. With this car being so light from its severe lack of goods, we may be able to get away with the supercharger for a bit longer. At length, after this top swap, it will be time to contact Ed Morad to pick up a 4T65-E HD and SII SC.

Lastly for this post, if I can pick up a nice Gen 2 Series 1, I could use the block for some bore & stroke project for my 94 SSEi. Whee.
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Old 11-19-2007, 02:10 AM   #8
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Rad, I am guessing that you already know the hazards of this "operation" you are planning and you just doing this to see if you can. Many people are going to tell you it can't be done or 50 reasons why it shouldn't be done. If your doing it for the hell of it all I can say is please be careful and take lots of pics.
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Old 11-19-2007, 03:09 AM   #9
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Quote:
Originally Posted by roadtech195
Rad, I am guessing that you already know the hazards of this "operation" you are planning and you just doing this to see if you can. Many people are going to tell you it can't be done or 50 reasons why it shouldn't be done. If your doing it for the H*** of it all I can say is please be careful and take lots of pics.


Thank you very much. So, considering that both my friend and I know we're doing this because we really want a supercharger in an 89 LE, can we be assisted by the members here? I promise we won't brag about "how easy it is."

I read on here someone with a BMW wanted a large pulley for an M62 that he wanted on his car. We sent him to an eBay auction for a 4" pulley that fits over the shaft and has that notch in it. I think this was for a Cobra or something. Does anyone recall that? I really don't want a 4", but it'* a start on where to find such a pulley size.
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Old 11-19-2007, 03:18 AM   #10
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How do I know what the diameter of the pulley'* hole should be? Also, here'* a 3 5/16" pulley:
http://cgi.ebay.com/ebaymotors/ws/eB...EF:MOTORS:1123
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