2512cc Opel 8V CIH Competition Engine

Exhaust Manifold & System

A new tubular 4-2-1 exhaust manifold and exhaust system is to be made by Tony Law Exhausts, of Leeds.  Jim Garrard, who did the work on the cylinder head, supplied the tuned manifold specification to suit his head work.

Primary Pipe Diameter - 1.75" (44.45mm)
Primary Pipe Length - 17" (431.8mm)
Secondary Pipe Diameter - 2.25" (57.15mm)
Secondary Pipe Length - 14" (355.6mm)

The manifold specification could not be followed exactly (specifically primary pipe lengths) due to space constraints within the engine bay, and location of the inlet manifold, throttle bodies and air box.  The air box will not be fitted until the head is back in the car, so that it can be located away from the exhaust manifold and bonnet.

I decided that the previous ceramic coating on my exhaust manifold was not going to be up to the job of significantly reducing the under-bonnet temperatures, or be very long lasting, after talking to other people who have tried the stuff.  The exhaust manifold already rust spots showing through on some of the welds, and a couple of minor scrapes had gone through to bare metal, and it hadn't even been fitted.  I was put onto another company by a mechanic for a local Ford Puma WRC Rally Car (Escort WRC engine & running gear).  This company, Zircotec do a much more robust and effective insulating coating for exhaust manifolds called Thermohold GP™.  This coating is bonded onto the exhaust manifold, so it won't flake off like the other spray on product.

The new ceramic coating should allow the heat to be transmitted further down the exhaust, so reducing the under bonnet temperatures.  I have decided not to use exhaust wrap this time, as I did on my last 2.4L engine, after having seen the distortion and damaged it caused to my previous manifold, in only 500 miles (800 Km).

The exhaust system is a 2.75" three box system, which can be disassembled for repacking, and was also specially made by Tony Law Exhausts.  It is a straight through 3 box system, which should allow the car to pass noise testing, which is now down to 95dB at some events.  My previous 2 box system, used with the 2.0L engine until 1999, was giving out 108dB, which would get you excluded just about anywhere now.

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Last updated: Saturday, 25 September 2004.