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CIH 16V Head

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Take a look at the Latest News Section for the CIH 16V Head Project.

Project Introduction

I compete with my Manta in UK Motorsport Association Hill Climb events.  The class of vehicle in which I run is the Modified Production Saloon Class.   One of the requirements of this class, is that I must use the original engine block for the vehicle that I am using.

I am running a 1979 2.0L Opel Manta SR, so I must use the Opel 2.0S CIH block.  Within this block I am using an 85mm stroke crankshaft and 97mm diameter pistons giving 2.5L capacity.  A modified Opel 2.2L CIH cylinder head which gives better flow characteristics than the original 2.0L head.

Together with Kerrie Thornton, another local Manta enthusiast, we hope to cut down and modify a 3.0L 6 cylinder 24V twin camshaft head, from the Omega/Senator, to produce a 16V head for the Opel 2.0S CIH block.  If the project is successful, I hope to run this head in my Manta, so giving a 2.5L 16V engine.

Risse Motorsport 292PS 2.0L 16V CIH Race Engine

Risse Motorsport 292PS 2.0L 16V CIH Race Engine
Here is a picture of the Risse Motorsport 16V CIH Race Engine, picture kindly supplied by Dietrich Risse.  This engine is 2000cc and has 292 PS on the dyno!  Maximum engine speed is 10200RPM!  This engine was built by Risse Motorsport in 1999.  The complete 16V engine or just the cylinder head are available from Risse Motorsport.  Many additional parts (inlet-manifolds, bigger valves, valve-guides, camshafts, twin valve springs with all caps (titanium), head gaskets) are available from Risse Motorsport for both the 16V and 8V CIH engine.  Have a look at their website, where you can buy all these parts on-line.
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The 6 Cylinder 24V Head

Here are a few pictures of the 24V head as it was stripped and cleaned.

The Opel/Vauxhall 6 cylinder 24V Dual Ram head

The exhaust port, nice and clean with little restriction

Inlet tract removed

Note the simplex cam chain system.  This will have to be replaced with an adjustable duplex chain system if we are to rev the engine above about 7000RPM.

Rocker cover removed

A clean view of the casting

The combustion chamber.  Note how close the injectors are to the inlet ports on the standard engine.  This assembly could be used, as is, if we require a twin fuel injector system

Combustion chamber with valves removed.  It may be possible to increase the inlet valve size by 1 or 2mm.  This picture also shows the poor cross-sectional area of the inlet tract near the valves.

The inlet port.  Much work to be done here to get good gas flow

A clean view of the oil galleries
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Visual Comparison between a 2.0 16V Head and an older 3.0 24V Head

In this section I will compare the 24V head against the newer design of the 16V head from the Opel/Vauxhall all alloy engine.  The 24V head is quite an old design, and there may be aspects of the newer 16V head which can be incorporated into the 24V head, to help increase gas flow.

Inlet Port Comparison

This picture shows the inlet ports of the two heads.  As you can see from the picture, the shape of the ports in the two heads are quite different, but have similar cross-sectional area.  The oval shape of the 16V inlet port probably also gives better sharing, and straighter flow, of the gas between the two inlet valves.  Dependant on the excess material in the 24V head, it may be possible to elongate the inlet port horizontally to give it an oval shape also.

What is not obvious is that the inlet valves are aligned more perpendicular to the gas flow in the 16V head which will naturally give a better gas flow path into the combustion chamber, than on the 24V head.  There is nothing we can do to make this better in the 24V head.

Exhaust Port Comparison

As can be seen from the picture, the exhaust ports on the two heads are very similar in shape, but the ports on the 24V head are about double the cross-sectional area compared with those of the 16V head.

Since the exhaust gases are forced out of the combustion chamber by the action of the piston, I am not aware of any advantage in having large exhaust ports.  However, since we will be looking for maximum gas flow in the final engine, I do not think that there will be any disadvantage to having large exhaust ports.  However, if necessary, material can be built up in the 24V exhaust ports to reduce their size.

Combustion Chamber Comparison

This picture is not very good.  The inlet valves of the 24V head are about 4mm larger in diameter than those in the 16V head.

The exhaust valve alignment between the heads is almost identical.  However as discussed earlier, the inlet valves in the 16V head are aligned much better to the inlet port, so giving a straighter gas flow to the valves and hence into the combustion chamber.  Since the 24V head has quite a sharp curve in the inlet port and the valve faces are far from perpendicular to the gas flow,  most of the gas flow will pass around the valve only on the outside of the inlet port curve.  This means that the effective inlet port cross-sectional area is significantly reduced at the valves compared to the 16V head.  Hence the much larger inlet valves in the 24V head.

Much work will be required on the 24V head inlet ports to gain a significant increase in gas flow, when compared to the work required on the newer 16V head. 

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Work to Fit New 16V Head to Opel CIH Block

Here are our initial thoughts on the work required to transform the 24V 6 cylinder head into a 4 cylinder 16V head for the Opel CIH block.  Those items marked with a (*) may not be required, but further work will be necessary before a decision can be made.

  1. Cut two cylinders from 6 cylinder head        In progress

  2. Fabricate new end plate and weld to head

  3. Reposition head bolt holes in head to suit CIH block        CAD drawings complete

  4. Reroute oil ways in head to suit CIH block

  5. * Reroute water ways in head to suit CIH block

  6. Fabricate adjustable duplex chain sprocket for primary cam chain drive to the exhaust camshaft, and align with sprocket on crankshaft

  7. Modify primary cam chain guides and tensioner for duplex chain

  8. * Fabricate one fixed and one adjustable secondary duplex cam chain sprocket to drive inlet camshaft

  9. * Modify secondary cam chain tensioner for duplex chain

  10. * Fabricate extension plate for cam chain housing in head (if duplex primary and secondary cam chains used)

  11. Fabricate blanks for inlet and exhaust camshafts

  12. Fabricate new cylinder head gasket

  13. * Modify hydraulic tappets for fixed operation with high lift camshafts

  14. Modify camshaft cover and plug lead cover for new 4 cylinder head

  15. Modify head on gas flow bench for maximum torque (including new inlet and exhaust valves, valve seats and valve guides)

  16. * Fabricate twin valve spring seats and caps (may not be enough room in head casting to fit twin valve springs)

  17. Profile inlet and exhaust camshafts to suit flow benched head

  18. Fabricate inlet manifolds to suit 50mm DCOE Carburettors, or 48mm DCOE throttle bodies (with or without original injector assembly)

  19. Fabricate 4-1 or 4-2-1 exhaust manifold

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Latest News

Various cuts made in head
Kerrie has completed transferring the head specification to a CAD package.  This will allow most of the work on the head to be carried out by CNC machine.  This will make modifying further heads easier at a later date.

The first cuts have been made into the 24V head, as part of the process of removing two of its cylinders.  Pictures provided by Kerrie Thornton.

Kerrie is presently waiting for me to provide a spare block so that he can test drill it for a head bolt which needs to be moved.  Unfortunately the block is in the car keeping my gearbox in place until the new 2512cc engine is ready for installation.

I would like to thank Marek Gamola who has provided us with information about the work done on the 3.0-l race-engine used in the German Touring-Car Championship in the early 1990s.  This is the same engine from which we are hoping to develop a 16V head for the Opel Manta 4 cylinder CIH engine.

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For problems or questions regarding this web contact [Project Email].
Last updated: Tuesday, 18 May 2010.