My Mk3 8v to Mk4 8v Manifold Build/Swap/DIY

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My Mk3 8v to Mk4 8v Manifold Build/Swap/DIY

Post by midwestjetta » Sat Jan 20, 2007 10:22 am

So after having the manifold for about a year, i finally have the time and funds to get going on this...

My car is 98 obd2 so everything i do is in relation to that

Starting it off, Tonight i lengthened all of the wires for the sensors so that they would reach across the bay

this will be an on going thread, i believe up next will be gasket matching the new manifold, for that little bit extra

i will keep you all updated and when im all finished, i will give an extensive writeup with detailed pictures

***UPDATE 1***: It looks as if this might be happening sooner than expected. I will keep this updated

i made a slight outlie tonight, cause im OCD and get panicy if i dont have a list


heres the official write-up that i have put together:

MK4 Upper Intake Manifold
MK4 Lower Intake Manifold
MK4 Valve Cover
MK4 PCV Assembly
MK4 Oil Cap
MK3/4 Valve Cover Gasket
MK3/4 Manifold Gasket
MK3/4 Upper Manifold Gasket
MK3 Grommet for IAC Valve on Manifold
MK3 Elbow for IAC Valve on Manifold
(12) MK3 Injector O-Rings
5' of 3/4" Rad Hose
3' of 3/8" Rad Hose
6" of 1 1/8" Rad hose OR A Breather Filter that fits the MK4 PCV Assembly
Assortment of hose clamps

1. Unplug any and all sensors on the intake system (for me it was the IAT, PCV Filter, MAF, TPS)
2. If not already done (like i had done) lengthen all sensors wires so that they will reach to apporpriate places, i personally just lengthend them all to reach the fender.
3. Take off intake
4. Unhook FPR from the manifold
5. Remove upper intake manifold, 4 bolts up front, 1 in the middle, and 2 in the back
6. Remove throttle body from manifold
7. Carefully unplug the injectors and remove the fuel rail from the lower manifold. There are 2 or 3 bolts holding the rail onto the lower piece.
8. Remove the lower manifold, i believe there are 5 bolts into the head
9. Unhook the PCV assembly from the plastic pipe
10. Take off the valve cover.

1. for the TPS sensor that is located on the old manifold, take a 19mm boxend wrench and remove it from the old manifold
2. Take the new mk4 manifold and drill a 3/8 hole into the backside of the manifold, under one of the vaccum ports. Thread your newly drilled hole with a m12x1.50 tap.
3. Install TPS into new manifold.
4. On the fuel injectors, remove the old o rings. After you remove these rings, you will see a yellowish plastic ring on the injector, carefully cut them off all of the injectors. ONLY cut the plastic rings, DO NOT remove the plastic yellow cap. on the tip of the injector.
5. When you have removed all of the rings, put 2 o rings in the space, this will insure a good seal.
6. Other DIY's said to make brackets, I did not have to, the manifold was plenty strong, as well as some had to trim the fuel rail, i did not, it fit fine.

1. First, install the new valve cover gasket along with the mk4 valve cover, when i installed mine, i had to use a mk4 gasket, because the valve covers are different in shape, though it still fit fine.
2. Next, Bolt on the new mk4 lower manifold with the new gasket.
3. Take the fuel rail and install it into the new lower manifold, push it in with slight force so that it stays in by itself, after this install the bolts on the sides of the fuel rail, this will get the rail to stay in place and into the manifold.
4. Plug the injectors back in correctly
5. Apply the upper manifold with the new gasket and bolt it on. there are small indents in between the runners to get to the bolts in the back.
6. Attach the FPR to the manifold.
7. Install the mk3 throttle body upside-down with a new gasket.
8. run the throttle cable (you should install a vr6 throttle cable as the 8v one is just barely long enough) i have not yet, because i dont know how :banghead:
9. Plug in all sensors and make sure they are clear of anything that could damage them (fans, belts, exhaust)
10. Install intake.

1. On my manifold there were two vaccum plugs, i attached the one on the rear of the manifold to the hoses near the pass. fender. and the one on the left hand side of the manifold to the throttle body.
2. i cut the plastic PCV pipe and ran some hose between it so that it did not have to flex and strech
3. BEFORE you start the car, make sure every single vaccum line is attached and that everything is plugged in and connected, it will save you alot of frustration later on.
4. Start car, test drive, enjoy

:thumbup: :thumbup: :thumbup:

if you have any questions, IM me and i will add them in a Q/A section

thanks to corey for the help, we blasted through this, it took us in total about 4 hours not including parts scourging, lunch, and being lazy. :beer:

Ok, heres some updated pictures, i still have to get the installation pictures but these are after i applied the heat wrap and hid the wiring, i am aslso running a little "velocity stack" that i made out of spare plastic, i still need a filter for it though.

the manifold:

I hid alot of the extended wiring under the manifold inside of the wrap:

this is a bad image, but allows you to see where i placed the IAT sensor on the back of the manifold:

my ABD big bore wrapped up:

I managed to adjust the throttle cable enough so that it is not bent, or stressed, its worked this far and i havent had any problems:

and the "velocity stack":

Thanks to Corstarxxx, heres the build pictures

Heres another picture of the sensor location that i drilled:

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