Thread: Top Swap Info and Faqs, Also lots of 3800 Info

Simplest is just to keep the L36 EVAP system. It would connect to the L67 TB the same way as it does the L36 TB. Only difference is you would need to block off the line that normally goes to the L36 FPR.

If you want to switch to the L67 setup, the main difference is that it's mounted on the back of the engine instead of the front. A bit of rerouting, but nothing too difficult.

You need to run the l67 map, it has a bracket for it and it bolts to the supercharger.

Originally Posted by beastin1

30 - Run a vacuum line to the fuel pressure regulator and the MAP. The fuel pressure regulator needs to see boost in order to operate correctly. Go ahead and attach the Boost Bypass Valve to the supercharger. It's held on with a bracket and two bolts. Run a vac line from the tree on the supercharger to the top nipple on the BBV. The bottom one needs to see ATMOSPHERE, because our L36 PCM's cannot control the BBV.

31 - We can now put the exhaust back on. First, connect the HVAC, EVAP and Brake booster vacuum lines. For the exhaust, a 3 inch downpipe should be used to get the most out of your swap. You will need a new gasket for the manifold-downpipe and then downpipe - resonator. Transfer your oxygen sensor and hook it up to the harness.

Okay I might be doing a stop swap soon on my 1999 GP GT. My dad has got a deal on a Buick Park Avenue that has an L67 with a broken harmonic balancer. He wants to do a top swap on my GP. He is pretty savvy under the hood and generally familiar with working on 3800s, but I'm sorta doing the homework before we get into this. He has this whole thread printed out and is gonna look over it. However, I have a few questions:

1. In step 30 (it was just rather confusing), what exactly are we doing? IIRC, we are buying new vacuum lines and adding something that is NOT already on the L67. The reason I'm saying it's not making sense is because if the BBV is ON the supercharger, how/why am I running a vacuum to a tree on a supercharger?
Also, where/what do they look like are the FPR, MAP, and BBV? What should I be looking to do exactly with the 3 of these and a vacuum line? I understand that I will need the L67 MAP sensor and its connector.

Maybe all of this will become very obvious once we start working with the L67 as it is WHOLE and hooked up to the Park Avenue.

2. Is the 3in. downpipe an ABSOLUTE must? I'm pretty sure Dad's gonna want to keep it pretty much stock, so will my GT stock exhaust system be fine?
I read various things about KR and how the downpipe and the U-bend delete would reduce that. And I understand that with more compression and boost you would need more breathing room. But, what I'm not understand is if this top swap is basically making a stock L67 in my GP, then why is there a problem if the L67 basically rolled off the assembly line like this?
Also, we don't have any readers or anything. Dad has a friend that check the engine codes. What is needed to check for KR? What ALL takes it away and what all makes you HAVE KR?? EDUCATE me on KR info. hahah

3. Is the CAI an absolute must as well? Will my GT stock air intake box do just fine?

Other than that I think we can make our way through the steps.
IIRC, we will need the top of the L67, the MAP sensor and its connector, the L67 Throttle Body, and L67 Injectors/Fuel Rail and will have to twist the fuel line's end to fit in the L67 rails.

I just want to make sure I'm getting all bases covered. I'm sure we'll run into something else later on, but this should get us off to a good start. Since my GT is not running right now, is it fine to remove the fuel rail without releasing all the fuel by turning it over? The upper intake is off of my L36 at the moment. The fuel rail is off but not disconnected from lines or anything.
Also, we JUST put a LIM gasket on my L36 in the GP. Must that change/must we undo that; are they the same as the L67?

So other than my questions (sorry, just trying to get it right), I need to get my Grand Prix GT's PCM tuned for the Top Swap and other than that my swap should be smooth with new bolts/gaskets/etc?

Thanks so much! I appreciate any and all help on this.

Brandon. Pretty sure everyone has told you to read the safely modding thread...and if you have you wouldn't be asking what KR is because there is a sticky there that explains it all to you. This thread is very useful and explains the entire top swap too...you HAVE TO HAVE BREATHING MODS. No...maybe...or just a U-Bend delete...like HEADERS...you NEED HEADERS. Not a 3" DP and nothing else. I would never do a high compression built without doing AT LEAST headers if not having the heads ported.

Sorry, must've missed the KR sticky. I read it now, thanks.
And after reading the top swap thread word for word, step 30 just doesn't make sense.

Originally Posted by brandonl2000

Sorry, must've missed the KR sticky. I read it now, thanks.
And after reading the top swap thread word for word, step 30 just doesn't make sense.

what part of it did not make sense? You are going to have to be a little more specific if you want help...

Originally Posted by Liquifire

what part of it did not make sense? You are going to have to be a little more specific if you want help...

Okay. Step 30 is pretty much the only one that is losing me. The bit about running a vacuum line to the FPR and the MAP and running a vacuum line from from the S/C tree to the BBV's top nipple. And then it starts talking about the L36 PCM.
I'm not just scrambling parts together, I have a together L67 that I want to swap the top into my GP.
So maybe a little more explanation as to where at/what the FPR, MAP, and BBV look like.
And as far as the PCM, I intend to have my L36 PCM tuned for the top swap before starting it. So I was just confused as to why it can't control the BBV.

Which, like I said, I may be confused for no reason as I haven't seen what the L67 has and identified the individual parts yet.

But thank you for the help.

The FPR is on the fuel rail, and the MAP is on the back of the blower. Both of these need to see boost, so they need to be connected to a vac line after the blower. The BBV actuator is the black canister on the front of the blower. You will need to connect it to a vacuum source before the blower, which is what that manifold (tree) is. This opens and closes the BBV based on manifold vacuum, which is a good thing. Normally on the L67, the actuator is also connected to a solenoid, which is connected to vacuum after the blower. The computer controls this solenoid to force the BBV open for things like traction control. Flashing an L67 bin to the L36 computer has been hit or miss on whether it can control that solenoid or not, so the general recommendation is to just leave it vacuum controlled and not worry about letting the computer interfere.

okay thank you. that helps A LOT. but what do you mean by before and after the blower?

So from the L67 on the Park Avenue, will the vacuum lines I need already be there and I just re-route them according to how I need it on the GP? Or am I running all these new lines?

blower = supercharger. I'm talking about before and after the air is compressed. The air comes into the throttle body and into the blower. This is before. After it goes through the blower and into the lower intake, it'll be at higher pressure. This is after.

The vac lines should be the same, the only change you'll need to make is on the BBV. Normally there's a line going from the FPR to the BBV solenoid, you need to eliminate.

i knew what blower meant! lol

but thanks for explaining, that really helped a lot.

The L32 block the same between W-bodies and F-bodies? I know they're the same motor, I'm wanting to know if the mounting locations are there for all platforms.

Well, I know in the LSx world, the mounting locations are always there, sometimes there are bolts for mounting accessories that are not drilled out from the factory (different accessory drives).

I thought that I read somewhere that any of the motors can be put into any of the platforms, just want to make sure so I can broaden my searching for a new motor.

That's what I meant, always get the numbers confused. Just wanted to find out if the f-body motors can be swapped into w-bodies.