Link to Opel Manta Owners Club myopels pic Link to Opel Tuner's Source

Cylinder Head

Home Up

Home
Up

 

2512cc Opel 8V CIH Competition Engine

Cylinder Head Specification

Initial porting work in progress Scribe marks show limit of initial porting No work yet done in combustion chamber, original seats not yet replaced Looking from valve side, shows how much work is still to be done A view along the inlet port A view along the exhaust port Polished combustion chamber, still awaiting inlet v/v seat & exhaust v/v guide New inlet & Exhaust valves with 5/16" (7.94mm) stems, note valves not wasted Valve heads are flat, to help keep static compression up A better view of the back of an unfinished valve head Special competition valve guides Rocker Arms & Stud Girdle

The cylinder head originally came from a Vauxhall Carlton 2.2l engine.  This head is very similar to the 2.0L Manta head, except that the inlet ports sit about 20mm higher in the head and it has larger valves, so giving better airflow as standard.  The design requirement for the head is that it should run on Super Unleaded Petrol (97-98 RON), and should maximise the torque to be delivered by the engine throughout the rev range.  With this requirement in mind, this head has been given to Jim Garrard of "Competition Cylinder Head Developments" in Driffield, East Yorkshire, England.

 

The finished cylinder head Head porting has been completed Ports, valve seats & combustion chambers A closer view of the inlet & exhaust ports Modified Inlet Valve Spring Locator for new Dual Valve Springs Timing in the Camshaft Final flow graph for the new head

The final specification for the 2.2l head is as follows:

Special competition 5/16" (7.94mm) valve guides
Special Inlet & Exhaust valve seat profile
47mm Inlet Valves with 5/16" stems
40mm Exhaust Valves with 5/16" stems
Crower Dual Valve springs (installed height 1.600" (40.64mm))
Modified Inlet Valve Seats for Dual Valve Springs
0.300" (7.62mm) Deep Exhaust Valve Spring Seats
Special Piper Cams 290° duration solid lifter Camshaft with 12.60mm valve lift
Cam Effects Roller Rocker Arms
(ratio is about 1.557, Opel rocker ratio is 1.52)
Modified Opel CIH Hydraulic Lifters (with flat top insert)
Cam Effects Stud Girdle & Poly-Locks
Hardened EN24 Steel Dual Valve spring Caps
Kent Vernier Camshaft Pulley
Modified Risse Motorsport thermostat housing

The new flow graph shows the inlet and exhaust port flows, using the 47mm inlet and 40mm exhaust valves.  The valves have 5/16" (7.96mm) stems, and the valve head profile is very different from the standard valve, looking more like a flat head nail than the tulip shape of the original Opel valves.  I have included the flow results taken from the standard head before work started, and the flow results for the SP Performance head.  Jim Garrard of "Competition Cylinder Head Developments" in Driffield, East Yorkshire, has done a computer simulation on both the SP Performance head, and the development head, and says that the new head could give 20-25% more peak power, at the flywheel, even though we will be using a cam profile with a 10° shorter duration.  The SP Performance head when rolling road tested, by Emerald Cams in January 2001, gave peak power of 194BHP, at the flywheel.  Jim puts most of this expected increase in peak power down solely to the increase in exhaust port flow, which has been increased from 65CFM, on the SP Performance head, to 96.8CFM (@ 0.500" lift) on the finished head.  Average torque at low to medium RPM will be increased dramatically compared to the SP Performance head.  The increase in this torque is due to the much better port and valve head profiles.

We are using 5/16" stemmed valves, and special competition valve guides have been made.  Originally we had intended using Triumph TR6 5/16" guides, but there was no way to ensure the guides couldn't slide in their bores, so we are having special valve guides made from a special material used by the Formula One Teams.

Based on the head, combustion chamber and port layout, new inlet and exhaust valve profiles have been developed, to allow maximum flow.  These valves will have 5/16" stems and weigh significantly less than the average competition valve.  The valve spring rate will be chosen to match the valves and the rest of the valve train components.  New valve seat inserts have been manufactured and installed for the inlet valves , which have a diameter of 47mm.  The exhaust valve seat inserts will not be replaced, but re-cut, as the valve diameter is to stay at 40mm.  The valve throat profile is quite complicated, having about 7 different angles between 35 - 75°, all cut using a single tool.  The actual valve seat is 1.5mm wide at an angle of 45°.

When the head porting was complete, the engine was computer simulated, and the optimum camshaft profile and duration selected for best overall performance.  The actual (I have checked it) cam profile we are using is as follows:-

  Inlet Exhaust
Rated Duration (°) 287 292
Opening Events (°) 33 76
Closing Events (°) 74 36
Duration @0.050" (°) 240 244
Opening Events @0.050" (°) 10 52
Closing Events @0.050" (°) 50 12
Duration @0.200" (°) 146 149
Lobe Centrelines (°) 110 110
Gross Tappet Lift 0.318" (8.08mm) 0.327" (8.31mm)
Gross Valve Lift
(Rocker Ratio=1.557)		 0.495" (12.58mm) 0.509" (12.93mm)
Lobe Separation 110°
Overlap 69°

The camshaft manufacturer was Piper Cams, in the UK, using one of their Opel blanks as a starting point.  Because we will be using a static compression ratio of about 11.5:1, the camshaft duration can be kept down to around 290°, to maintain a suitably high dynamic compression.

Since we will be using 12.58mm (Inlet) and 12.93mm (Exhaust) of valve lift, and a 290° (average) short duration camshaft, the acceleration slope of the cam will be quite extreme, even for a solid lifter cam.  With this in mind, the Stainless Steel valves (using a 5/16" stem diameter) and solid lifters (modified hydraulic lifters which are hollow inside) are as light as possible, so that the valve spring rates can be kept to a minimum.  This should ensure that the stress put on the Cam Effects roller rocker arms and Opel solid lifters is kept to a minimum.

Dual Valve Springs with the new Spring Caps Top & Bottom view of the double spring caps Sketch of Inlet & Exhaust dual Valve Spring Installation Double Spring Exhaust Valve Seats fitted to Head Modified Inlet Valve Spring Locator for new Dual Valve Springs

The new Crower dual valve springs have an installed height of 40.64mm (1.600").  The spring rate is 255lb/in, and gives a seated pressure of 93lb/in.  The spring set ID is 0.750", OD is 1.350".  I want to get the installed height of each spring to within 0.25mm (0.010") of each other or better, most manufactures suggest all the spring heights should be within 0.50mm (0.020") of the designed installed height, so that all valve seat pressures are as similar as possible.  As it happens, the installed height of 1.600" (40.64mm) is almost perfect for my valves and spring caps.  In the case of the exhaust valve springs, a 0.300" (7.62mm) deep seat/locator is required to replace the original Roto-Caps.  Only one of these spacers had to be reduced in height by 0.015" to get all the exhaust valve heights matched.  To fit the inner inlet valve spring it has been necessary to reduce the diameter of the original inlet valve spring locator to 0.750" (19.05mm), as shown in the sketch.  For the inlet valve springs, the chosen installed height is 1.590" (40.39mm") ±0.005" (0.125mm), as I didn't want to cut into the head again to reduce the height of one of the inlet valve seats.  I needed two 0.015" and one 0.030" shims to get the inlet valve installed heights matched, and these had to come from the USA because there is no off the shelf shims available in the UK.  Apparently nobody bothers to match valve spring installed heights in the UK.

Cut away of CIH Head with Cam Effects Roller Lifters/Rockers installed My new Roller Rockers Poly Locks for the new Roller Rockers Roller Rockers and Stud Girdle Trial Fit on my Head Roller Rocker when Valve is in fully open position Roller Rocker when Valve is in closed position

I am using the new roller rockers from Cam Effects Inc.  These rockers have a roller at both ends, and are actually a copy of the design developed by Bob Legere, with a rocker ratio of 1.557.  With a roller at both ends, these rocker arms will put very little side loading on the valve stems and the solid lifters, which should give better reliability and longevity.  Most self-aligning roller rockers are designed to be used with 3/8" or 11/32" valve stems, so Cam Effects have modified a set so that they can be used with my 5/16" stemmed valves.  I will also be using the Cam Effects Stud Girdle and Poly-locks to hold the roller rockers in place.

The Vauxhall Frontera 2.4i Rocker Cover, slightly modified Breather cover plate removed, and ribbing cut back Another view of the cut back ribbing, and the rubber gasket Replacement smaller breather baffleNew paint job & oil filler cap

An unmodified rocker cover cannot be fitted over the roller rockers and stud girdle, without using a spacer plate and two cork gaskets.  Since it now seems unlikely that a spacer plate will be supplied as part of the Cam Effects Roller Rocker kit, I decided to see if it was possible to modify an alloy rocker cover so it did fit over the roller rockers and stud girdle. As I have have never had much luck in getting the cork rocker cover gasket to seal properly, even with liberal use of Sikaflex-221 Polyurethane Sealant (it works perfectly on my engine sump, go figure!), I have decided to use the 2.4i cover from a Vauxhall Frontera, which has a rubber sealing gasket (Vauxhall/Opel Part No. 90322930).  (Note: the rubber gasket doesn't fit the 2.2i cover without modification, I've already tried it!)  The internal ribbing in the rocker cover was cut down until they were only 3mm deep, on a milling machine.  A new smaller breather baffle plate, made from 1mm aluminium plate, has been tack welded to the cover.  The bottom left picture shows its location.  I have filled the new baffle with competition fuel tank foam, in lieu of the original steel mesh.  The rocker cover has been repainted, and a new posh oil filler cap purchased.

Flat top lifter designed/supplied by Bob Legere Lash Caps for lifter as supplied by Cam Effects Sketch showing Flat Top Lifter My new flat top inserts & modified hydraulic lifter bodies lifter005.jpg (120558 bytes)

The Cam Effects Roller Rockers come with Lash-Caps for the Opel solid lifter.  However, I prefer the original Bob Legere design using the hydraulic lifter and flat topped insert, which don't have the small added risk of lash-cap failure.  As you can see from the pictures, my new flat top inserts are very similar to those designed by Bob Legere.  They were manufactured in "Silver Steel" and heat treated.  The specification for "Silver Steel" is available at http://www.westyorkssteel.com/u.k/Product_Info/Tool_Steel/silver.htm, and are about 16 grams lighter than a solid lifter and lash-cap.

Future Options

Cam Effects Roller Cam Kit Roller Cam Profile for Opel CIH Engine Roller Lifter Drilling Jig CIH Roller Lifter and Sleeve Drilling Jig is used to drill a hole for a set screw which holds the lifter sleeve in place

I am hoping to install a Roller Camshaft and Roller Lifters from Cam Effects Inc. sometime next year.   Like the Roller Rockers, sourcing a manufacturer was part of an Opel Tuners Source project, check out the site for the latest information.   Bob Legere in the US has ordered five roller cam and lifter sets.  So far he has installed one kit in a 2.5L Opel GT.  Info about the installation, pictures and results can be found here on the Opel GT Forum.

Back to Top
For problems or questions regarding this web contact [Project Email].
Last updated: Saturday, 25 September 2004.