The biggest problem that I had with the car after fitting the turbo’s was the exhaust system. This started out life with stainless manifolds & a straight through pipe from the turbo outlet! This sounded very nice if a tad on the loud side! It was however too loud for travelling any distance & on checking the sound level for competition (1m from outlet & 2/3 rpm) the needle went straight off the 120 Db scale!!! This meant it was far too loud to run in hill climbs etc, especially at circuits like Goodwood which had a 105Db limit. All my theories about the turbo’s taking most of the sound out of the exhaust were wrong.
The first attempt at a solution was to fit some baked bean can type silencers on the ends of the exhausts- straight through of course. This helped but not anywhere near enough, now we were on the sound meter all be it at around 120Db. Then came an oval silencer on the end with some slight baffling & twin outlet pipes, these were also packed with wadding which could be replaced-- result 115Db - still to much. It was suggested (by who I forget) to fit a balance pipe between the two separate exhausts but this only made it louder.... In a desperate bid to get the car ready for a hill climb, some additional baffles were fitted & one of the outlets on each Silencer was blinded off- this got the level down to 110Db for the sound check which was the aim, but of course these drastic measures were seriously strangling the engine at anything above 4000rpm. All this messing around & lost power/ acceleration & there was not even a sound check at the hill climb - life is a bitch at times.
Back to the drawing board again. It was decided to go for two transverse mounted round silencers 24” long & 5” diameter with a 2-1/4 bore, of the straight through type, join the two turbo outlets together & then through the silencers in series. This worked very well in silencing the engine to about 95Db (nearly too quiet) but at high rpm the engine was having trouble breathing - you could feel it holding back. The exhaust piping was modified - again- this time one turbo outlet was routed through each silencer & the result was finally a success, 103 Db without choking the engine.
So with that fixed , I thought that there would be no need to worry about the exhausts anymore , but as usual I was wrong. The next problem was with the manifolds. These at first were fabricated from stainless steel, having an individual flange for each cylinder & using 1.5mm wall tube. These worked fine for a few months & then started to blow at one of the flanges. On removing the manifolds they were found to have distorted but using new gaskets, a big spanner & lots of assembly paste fixed the problem for a few more months. A bigger problem developed in that the manifolds would crack, probably due to the high temperature (nearly 1000 deg C) & resulting high stress. The worst example of this being one day when the exhaust started to blow while out driving & one turbo fell off before I managed to get home. It was left hanging on the oil & water pipes!!!!
A second pair of manifolds were then made using mild steel 2mm thickness & a single flange for the cyl. head, the idea being that mild steel would stand up to the heat better (wrong again), these also suffered from distortion & cracking. The distortion & leaking at the joint to the head was cured by welding a ring to the flange around each exhaust & then machining a corresponding groove in the cyl. head. This worked fine until a hole appeared in one manifold due to the steel being eroded away, back to the drawing board again.
The engine was then fitted with 2 new stainless steel manifolds fabricated using 12mm plate for the flanges & 4mm thick wall tubing sealed to the head with rings. These also suffered from distortion!
Finally I decided to reposition the turbos slightly in order to allow longer manifolds & had some more manifolds made – these were fine until the cars demise a year later.
The last change of exhaust manifolds mentioned above meant that the exhaust housing on the turbo would have to be rotated relative to the bearing housing. When the housing was removed to do this you could see that the tips of the turbine blades had melted. Turning up the boost over the years I had passed the point where the injectors could supply enough fuel – resulting in an expensive repair bill for new turbo’s and new injectors.
The standard Alfa box worked fine at first, this box had 30000 miles on it when it was first fitted & did another 15000 before the engine was turbo’d. After about 2 years & ten thousand miles of pure abuse from me & a turbocharged engine, the box started to whine a little, this I ignored (a mistake) as the noise didn’t appear to be getting any worse. A while later the clutch started to play up, engaging all by itself while sitting in traffic queues - interesting to say the least. I didn’t make the connection with the noisy gearbox, until eventually the clutch made some horrible grating sounds & I was forced to take out the engine / box & have a look.
On splitting the gear box from the engine, the clutch was ok but the gearbox input shaft bearing had a lot of play in it. When the box was dismantled I was amazed that it had lasted to get me home at all. The input bearing had no cage left & the balls fell on the floor. At the other end of the input shaft, the double bearing had broken in half & chewed up the casing. On further inspection 2 syncro’s had had their day as well as fifth & reverse gears.
The LSD was saved & another box found, which had been fully overhauled, including having the input bearing changed to a later (stronger) roller type. The box also had fitted the lower ratio diff gear out of the cloverleaf car, giving a ratio of 3.11 instead of 2.94.
The drive shafts failed once & of course just when I didn’t want them to, that was sitting on the start line for a sprint meeting at Aintree. The light went green, I dropped the clutch, there was a loud bang from behind me & the car just rolled over the start line. The shaft had failed at the root of the spline, at the inboard end & as so remained captive in the CV joint with no other damage. After a trip home on a breakdown truck it was decided to avoid the expense of having special shafts made but carry a spare. The shaft that broke was after all very old & had seen many drag races, sprints etc. before it gave up.
The Tilton clutch worked fine until it was suggested by a passenger that I might make a better start if I dropped the clutch in second gear instead of first. I willingly (or should that be stupidly) obliged & a brilliant take off was made. When it was time to change to 3rd gear the clutch didn’t work. It was found that instead of the tyres slipping, the clutch had done so instead it overheated & welded the plate to the cover. The clutch was upgraded to a twin plate version of the original which had twice the clamping force & was no further problem – I never did try a second gear start again though!
The oil cooler has been changed to a Mocal oil / water type. The old oil / air unit was positioned behind the driver, below the alternator, taking its cooling air from below the car. This was far from ideal as the air flow to the cooler was poor. The cooler needed to be repositioned, but where?. The decision was finally made by a rock, which holed the cooler. A Laminova cooler was purchased to avoid having to move the cooler into a good air flow.
The intercooler has had its fan removed as it proved unnecessary, there being sufficient cooling from the scoop. I have some temperature senders fitted & have seen 120 deg C into the cooler & 50 deg C out.
I also fitted a dump valve, not for the sound, but to help keep the turbo’s spinning on part throttle & when changing gear.
Following the breakdown of the gearbox, while the engine was out, I modified the offside rear corner of the chassis, making part of it removable. This allowed me to remove the box without disturbing the engine or turbos. I expected that the box would need attention sometime in the future.