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2,484 Posts
Discussion Starter · #1 ·
How to… Performance manifold into Mk4 Astra.


Performance manifold
Fitting kit
Gaskets - Not supplied with manifold. Can be purchased from Vauxhall or a local autofactor


Hydraulic jack and axle stands but preferably proper ramps or a vehicle lift.
Socket set with star sockets and extender bars
Spanner set
Adjustable pliers/mole grips
Angle grinder
Safety goggles


Ensure you have left the engine to cool sufficiently before starting as the components that you are removing become extremely hot extremely quickly even if the car has only been moved a short distance!!


Check you have all tools required and all of the parts for the manifold and fitting kit. There’s nothing worse than getting half way through a job and realising that something is missing, especially when you’ve just cut your exhaust in half!!

You have been warned!!

Step 2:

Move the metal and rubber pipe out of the way by removing the three bolts on the front of the block with a star socket then lift the pipes up onto the rocker cover out of the way.

Remove the dipstick and the rubber hose going in to the rocker cover, on the right using adjustable pliers/mole grips.

Remove the four bolts securing the heat shield using a star socket. Mine are allen key bolts as they are aftermarket ones but the standard bolts are star bolts.

Step 3:

Remove the ten nuts holding your old manifold in place ensuring that the engine has been left to cool as the heat will cause the metal to expand and can cause trouble when removing them. Some will come off with the stud still inside and some will come off on their own this is normal so don’t panic. If they have gone slightly rust apply some WD40 and allow it to soak in for a few seconds.

The three lower circles that appear empty show the approximate location of the bolts under the manifold.

Step 4:

Apply some WD40 and remove the two bolts holding the bottom of the manifold in place.

Step 5:

After removing the old manifold lay it next to your shiny new one and appreciate the craftsmanship involved in it’s construction while seeing the shocking difference between the two!!:D It’s easy to see why it improves exhaust flow when you see them like this!! Can you guess which is the new one??:p


2,484 Posts
Discussion Starter · #2 ·
Step 6:

Remove the lambda sensor with a spanner. I found this easier from underneath The vehicle.

Step 7:

The down pipe from the manifold is one long pipe that is welded in place to the CAT. As the new down pipe comes in two pieces, offer the front piece up to the old pipe and cut through the old pipe about 4 inches after it finishes. This will allow you to fit the manifold and front pipes then cut back the old pipe further to the required length. Just remember you can always cut it back further if needed but you wont be able to add it back on!!

Step 8:

Attach the new manifold and gasket with the ten bolts that you removed earlier. It’s best to lightly coat the gasket with oil to help create a better seal. Remember to tighten the bolts in an uneven pattern to spread the pressure on the gasket and keep an even seal. Then reattach the lambda sensor. Before screwing the sensor in, twist the cable round a few times, so that as the sensor tightens up the twists come out leaving less strain on the cable.

Step 9:

You should now be left with something like the parts below. Attach the down pipe to the manifold using the gasket and the four bolts provided.

Step 10:

The final piece of piping should have two slits in where it attaches to the CAT. These allow the new pipe to fit over the old one before you clamp them down. Offer the final section up to the end of the down pipe and put a mark on the old pipe about 1 inch before these slits start (approximately where my thumb is) so that there are no gaps left when the two pipes fit together.


2,484 Posts
Discussion Starter · #3 ·
Step 11:

Cut the old piece of pipe off at the mark, push your clamp up to the CAT and then push the final section over the top of the old pipe and twist it until it lines up with the down pipe.

Step 12:

Do up the bolts between the down pipe and final section ensuring a nice flush fit before tightening the clamp by the CAT.

This Lexmaul manifold had two bolts and two tapered springs to join the down pipe and final section. Push one of the springs over each bolt ensuring that the small end of the spring is pushed against the bolt head and the large side is pushed against the flange when tightening the bolts. This will act like the movable joint on the standard manifold.

Step 13:

Ensure all of the nuts, bolts and studs are tight around the manifold and then finally reattach the heat shield and piping. When you are happy that everything is in place fire up the engine and check that none of the joins are blowing before taking it for a test drive!!


This "How to" is intended to be used as a guide to give you an idea as to how to carry out the same work on your own cars. The instructions above detail how I carried out the work on my own car and as each persons car, tools, level of experience and circumstances are different then the steps required to carry out the work will vary from person to person and therefore myself and this website cannot be held responsible for any loss, damages or injuries caused while carrying out the work. If you are unsure in anyway as to how to carry out any of the work detailed above then consult a professional for advise or consider paying them to do the work. So take care while carring out the work because YOU HAVE BEEN WARNED!!
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