My Monza's 16V motor remained unchanged until January 2000. In December 1999, the alternator's earth strap came loose and touch against the intake manifold where it kept on sparking. This burnt a hole through the water channel causing the motor to overheat badly. So, I decided to bore it out to 2.1 when I rebuilt the motor. In January 2001 I decided to go further with the modifications on the car as I rejoined the Opel Owners Club after a two year absence. Firstly I installed a limited slip diff to help with the launch. I also decided to go with sidedraught carburetors. Fitting sidedraught carbs isn't always as easy as it looks. When you move down this page you will see why I say that.

When I bought the 16V engine it had the deep dished flywheel. I got this 'flat' flywheel when I bought the LSD. Upon swapping I weighed the two flywheels and there was an amazing 3.1kg difference! with the dished one weighing 9.7kg and the flat one 6.6kg. The most notable difference this makes is when launching hard or when snap changing the gears. the weight difference together with the LSD makes for a much more controllable spin and hardly any spin on gear changes.
The manifold is an imported manifold made by SB Developments in the U.K. As you can see it has straight runners and not angled ones. This makes for much better airflow.
The manifold is manufactured with a water channel similar to that of the injection manifold. Unfortunately it didn't have a water hose fitting.
I was able to find a hydraulic fitting with the same thread. It was a bit long though, so I cut it a bit shorter.
Here is the manifold fitted with the modified hydraulic fitting.
I also decided to go a step further and match the ports of the manifold to that of the cylinder head. Here you can see where I used a permanent marker to 'mask' the area where I needed to trace the new shape of the port.
My next problem was to make a bracket for the accelerator cable. I cut a piece from this metal channel and hammered it flat as you can see from the piece in the middle of this picture. I then made a cardboard template for the bracket. Later I found out that this metal was actually stainless steel.
Here is the finished version of the bracket.
Here you can see how close the one carb is to the one pressure limiting valve on the brake master cylinder. It is due to the manifold having straight runners. Upon pulling away and hard acceleration the carb actually touched the valve. This nearly caused major trouble for me as the carb 'broke' the valve one Sunday night during a dice. Fortunately I had lots of road and just enough pressure on the floor to stop the car. That same night I took the two valves out and put the brake lines directly into the master cylinder. I will be moving the master cylinder and booster to the left of the firewall so that I can actually fit air-filters.
I had to take a bit of metal off the one carb and the rear top edge of the alternator as the two were actually touching when you wanted to adjust the fan-belt tension.
Many guys might argue that side-draught carbs don't make such a big difference in performance, especially 40's. Well, I've got 40's and here's the proof that they do work. These two dynamometer printouts show the difference between standard fuel injection and side-draught carbs. A full 15kw on the wheels! Not bad considering that no jets or anything was changed on the dyno and that the carbs only have 34mm venturis. Just the CO's and synchronization was adjusted.
Here you can see I finally got a set of ram tubes. Apparently these are very important to get the air flow characteristics right. Although removing the limiting valves gave me more space, I could still not fit the tubes. The top brake line towards the front of the car was still in the way. So I grabbed it and started bending it to go straight from the master cylinder to the firewall as you can see here. It's not a 100% straight but at least it's not in the way anymore. The only filters that will fit here is the sponge 'sock' type. Otherwise I will really have to move the booster and master cylinder if I want to use any other type of filter.
I used this power file to take away some metal on the cylinder head so that the lobes of 288° cams I was installing had enough clearance.
Here is a photo of the two intake cams. The one on the left is a reground cam and the one on the right is the 288°. The 288's have about 5mm extra lift over the other cams.
This is what can happen if you slip a gear. The stripped gear you see here is third. I could have it repaired for about R850 but I'd rather try and get an F18 gearbox with long ratios. My reasoning for wanting long ratios is that I should get slightly better 400m and 800m times because of less gear changes. Top-end should be much better as I won't be running out of revs.
These two pictures show the plenum chamber I made to fit over the throats of the carbs. The first is of the wire frame work serving as my 'mould'. I used 1.6mm galvanised steel wire which is fairly rigid but you can still shape it fairly easy. I bent all the arches using piece and then solder a few more pieces into place to make the structure more rigid. The thin wire you see is soldering wire. I put it on the frame to give some support to the fibreglass matting. The second picture is where I finished the fibreglass work and cut a hole in the larger end for the air tube coming from the front bumper. The other end is 'lower' so that it won't interfere with the brake piping. The hole is 75mm in diameter and due to the spiralling metal reinforcing band in the air tube I was able to just 'screw' the tube into the hole.
I had to make this mounting plate for the plenum chamber. It is made out of 1mm sheet metal. I bolted two gaskets onto the carbs and glued a piece of cardboard onto the two gaskets to use it as a template for the holes in the plate. The two cords you see are shortened bungee cord tie down straps. These will hold the chamber into place. The chamber also rests on the two 'lips' I bent into the bottom edge of the plate.
Here is the chamber fully installed. The flexible air tube runs through the hole in the right inner fender to the front bumper. There are two big advantages you get from using this kind of setup. The first is the greatly reduced induction noise coming from the carbs and the second is that you feed cool air from outside the car to the carbs. The only drawback was that I had to remove the ram tube because there wasn't enough space to get the chamber over them.
The first picture is a view of the air scoop from outside the front bumper. This scoop is fibreglassed to the inside of the bumper as can be seen in the second picture. The air tube coming from the carbs is then attached to this scoop.

Keep an eye on this page as I progress with the work.

Last updated: 29 July 2003