Exhausts - RC40, Millennium and others tested

The recent rolling road re-test of the 1275 engine build I did saw an opportunity to do some exhaust systems testing.

I had noticed a few years back that the RC40 was being manufactured by a different process than the originals - giving rise to a change in the shape of the bends applied to the system. I had wondered if they would be causing a restriction at all - but hadn't had the opportunity to test it. The lack of expected power from the aforementioned engine lead me to investigate all possible angles from the tyre contact patch to the carb mouth. I found nothing that explained the 14 or so bhp I was 'missing'. After some application of the old grey cells I mentally narrowed cause down to one of two things - either the piston oil control rings were still causing excessive drag (75% of all internal friction of an engine is generated by the piston rings) or perhaps these new bends in the venerable RC40 were indeed causing a power loss.

SU Carbs - Connection, HIF type

Although there are a number of different versions of the HIF type carb, they all essentially share the same type of connection layout.

The diagram below depicts the most common type - the connections can be on either the right hand side (as illustrated below) or the left hand side. Some have the connections shared on either side. Whichever, the port functions are the same. It isn't essential the crankcase breather pipe be connected - you really don't want that choking crap from the crankcase spoiling your nice, fresh, fuel-rich incoming mixture - but it's obviously essential to block the port off if you don't. A blob of RTV Silicone is sufficient in most cases. To adjuster mixture - screw the adjuster in to richen, out to weaken. There may be a 'anti-tampering' cap in there on some carbs - just hook it out.

C-AHT772 (3.75”, C-AHT773 (5”), C-AHT774 (6”) WEBER INLET MANIFOLD KIT

Build the manifold up before fitting to the car. The two spherical ended joints screw into the inlet manifold using the flat washers and nuts to lock them into place. The 5/16” rod is a tight fit into the two joints and care must be taken when fitting. The two linkage brackets fit either end of the 5/16” rod outside of the spherical joints using the 5mm nut and bolt to secure. Fit the small rose joints either end of the threaded rod and fit to the throttle linkage on the side required for the Weber carb being used. The 5” metal bar fits in a vertical position to the manifold, secured on the original manifold studs when fitting to the engine.

C-AJJ4064 – 8 PORT CYLINDER HEAD

The combustion chambers are left in a basic shape only with a nominal 16.4cc which allows enough metal for those with the latest advanced ideas of shape to apply them and create the correct compression ratios for the desired use.

Valve and seat material specification allows use of unleaded fuel. Thoroughly clean the cylinder head before final assembly. Check that the small circlip is in the correct position in the valve guide at a point where the guide protrudes through the cylinder head beneath the valve seat. Place the valve spring seat over...

Historical Article - May 1993 - Maximum Side Draught

Maximum Side-Draught Carburettor Potential For many years now, the steel-formed inlet manifolds - produced by a well known steel tube manifold fabrication company in England - have been accepted as THE performance manifolds for side draught carbs. This was mainly due to the extremely poor quality and terrible basic design of the alloy cast manifolds on the market. There were one or two that were deemed on a par with the steel ones - and were supposedly multi-funcitonal to use SU's also - but were more expensive and not particularly readily available.