wooldrb

Went to a guy I know and he's offering a ported FC throttle body and the intake manifold that goes with it so that I can bolt it directly onto the engine. The only problem that seemed like it might crop up is the placement of the TPS. Can anyone shed any light on this? Are there other issues when swapping these components in? Are there other threads that touch on this (I searched and couldn't find anything)?

peejay

I've done a fair bit of swapping around between GSL-SE and FC engines and "bitsa" engines of the past couple years.

Assuming a Series 4 manifold and not a Series 5, here.

The intake manifold will physically bolt on to the engine, the end ports and injector air bleed ports will line up, and the plenum brace will line up. The TPS has the same connector and functions the same way. The main advantage to the S4 stuff isn't the larger throttle body so much as it is a better shaped plenum chamber and much larger secondary runners.

That's the good news.

The bad news is that the GSL-SE primary ports, while being the same height as FC, are in a different location. Short of pulling the engine apart and doing extensive runner porting in the center housing, you will have the bad kind of port mismatch - a step in instead of a step out.

I think but am not sure that the GSL-SE primary rail will clear the manifold. I know it won't clear the Turbo II manifold. You can plug the secondary injector holes with a set of injectors and fuel rail, just make sure to cap the fuel rail ends so junk doesn't get in the rail if you should ever decide to use four injectors later on.

You will have to do some work to the manifold to cover the ACV port in the center housing. I forgot that part! The S4 N/A manifold doesn't extend as far down as the GSL-SE manifold (or Turbo II for that matter) and it will leave that port uncovered. This isn't difficult to fix. I had a Turbo II block that I originally used a GSL-SE manifold on for expediency. (Huge port mismatch, to put it mildly) No exhaust leak. Put a Turbo II manifold on it. Still no exhaust leak. Put a modded S4 N/A manifold on it. Exhaust leak. I cleaned the manifold extremely surgically clean, put two screws into the bottom of the manifold for some bite, put some two part "stick" epoxy on the manifold, and filed it flat and to the contour of the TII intake gasket. You'll have to do something similar.

peejay

For what it is worth, I am probably going to embark on this project next week. Testing of my third-bridge GSL-SE block shows that the throttle body is a pretty big restriction. Manifold pressure is 96kpa (atmospheric) at full throttle but starts dropping over about 4500 (!) and is down to 89kpa at only 7000rpm. That's 2 inches of vacuum.

That, and I need to pull the manifold anyway in order to un-block the aux ports. The torque the engine has is nice but I want MORE POWER. I'm only seeing 70% duty cycle which corresponds to about 150hp.

Mind you, that's 15hp more than stock, with sealed-off aux ports...

wooldrb

Well, I just ordered my Racing Beat exhaust, and I'd really like to embark on the intake/throttle body swap as well. Let me know how it goes. If you would, post your progress in this thread. I'd love to see where it goes.

peejay

I'll take photos of the process. While I'm in there to cover the center air port, I'll rework the manifold to meet up properly with the center intake ports. Won't be ideal, but it'll be a whole lot less non-ideal.

peejay

Pictures time.

Here's an FC N/A intake gasket on a Turbo II center housing. The air port has been filled, but the exhaust leak that would result if it wasn't is obvious. (Yes, the header is on upside-down, this engine was used as a jig while converting a 12A road race header to 13B)



Here's an FC N/A center housing and a GSL-SE center housing side by side. Note that the air bleed holes are in the same spot, but the intake ports aren't. (You can also see where the FC intake gasket stopped)



FC N/A lower in vise. Red marks on ruler correspond to GSL-SE intake port boundaries.



The manifold has been thoroughly cleaned with non-residue solvent in the appropriate areas, the new port height marked, and two self-tapping screws run into the bottom to give the stick epoxy some bite.



Where we're at right now. The screws were cut off to about 1/4" away from the surface and half a tube of JB Stick Weld has been kneaded until tacky and worked into place. I prefer the heavy epoxy for things like this because they won't run while they set up. The bottoms of the intake ports have been filled with JB Kwik and some cardboard is clamped on to keep it from running out.

peejay

After a little bit of filing and porting we end up with this (GSL-SE outline in red):



I deliberately left SOME mismatch because I believe that it's not a bad thing, especially in a port that is shaped like this.

Here's a GSL-SE intake gasket on top of the manifold for comparison:



Note that it doesn't 100% cover the ports under the secondaries. I made my own intake gasket.

Other notes:

The GSL-SE throttle cable should work no problem. I was actually using an FC cable on the -SE manifold.

I was wrong about the manifold support. The -SE support is NOT the same as FC - the FC one is about an inch higher and is further out. I used the FC support and made new fuel lines.

wooldrb

Great write up. I'll definitely do this if/when I decide to finally go through with it. Just one question though: aren't you terrified the JBWeld will come off and get sucked into the engine, or is that not an issue?

peejay

Terrified? No. Respectful? Absolutely. That's why I make sure every area where the epoxy MIGHT adhere has been thoroughly scrubbed, cleaned, rinsed with water, blow dried, and then doused with non-residue solvent (brake cleaner, denatured alcohol) and allowed to air dry, so that there is nothing there but CLEAN, oil-free, water-free metal. Not even fingertips get to touch it.

I first epoxied up a manifold in the winter of 2000/2001. That was a shutter valve elimination on an FB 12A intake that used three or four (maybe five) cards of the stuff. (It wasn't worth the effort, power wise) Since then I've done a couple more 12A intakes, probably three or four 13B FI intakes including this one, and then there was the whole peripheral port project.

2GSLSE

iTrader: (6)

How many wires need to be changed/longer for the swap? any electrical issues to work around? I have a friend with a gslse and is going to use his S4 streetported engine/manifold but keep the gslse wiring if possible untill he can upgrade to an aftermarket ecu.

peejay

The GSL-SE fuel rail fits under the manifold just fine. The TPS and air temp sensor are in roughly the same spots, the air temp may have to be switched out though if the connector is different.

Beyond that, I have no idea. I'm not using a BAC or the ACV (or even a factory computer) but I'd imagine that a BAC is a BAC is a BAC, and I don't think the ACV would be functional anyway because of the fundamental port differences. Both engines have similar thermowax setups so that is just a matter of making the coolant hoses fit. (I'm not using that either)

One thing to pay attention to is that the vacuum ports are different. Some of the ports are manifold vacuum, some are ported vacuum, and some are not even vacuum at all, but filtered atmospheric. A couple of the ports on the GSL-SE manifold go to the secondary side, which will be different vacuum-wise than the primary side.

Since I'm not running any of the stock stuff, I map out where goes what and run the fuel pressure regulator to manifold vacuum, the vacuum advance can (only one for me) to ported vacuum, and the injector air bleed goes to an atmospheric feed. I've rerouted the brake booster to get vacuum from the primary side plenum as well.

j9fd3s

iTrader: (3)

the BAC valves use the same bolt pattern, so you can use whichever one fits the ECU.

the ACV is weird. the 86-88 NA ONLY uses ports in the end housings. EVERYTHING ELSE after 1981, uses a port under the primary intake ports.

so if you use an S4 lower on a gsl-se block it will NEVER EVER pass smog, and in fact the ACV will be blocked off.

you can use an S5 lower, with an S4 upper if you really need to pass smog

i went the other way on one of mine, it was an s4 block with SE injection, it worked GREAT except i couldn't smog it, because of the ACV thing

2GSLSE

iTrader: (6)

ok thanks I told him I didn't think it would be bad but wasn't sure what needed to be done, worst case we will use the GSLSE injection with its own manifolds and the S4 block.

jesseluck

iTrader: (2)

Ok so just to clarify I have a gslse tps and I would like to replace the faulty one on my s4 turbo. If I understand peejay correctly than I can do this?