Greetings. I am an amateur petrolhead from Spain, and just have grooved the cylinder head in my '91 Opel Calibra 2.0i coupe:
Engine is a gasoline EFI 2 litre (122 cid) inline-four SOHC 2-valve:
I did many mods, intake and exhaust porting, chamber polishing, back-cut, stem-thinned and polished valves, fresh piston rings, new intake manifold, 10 ºC colder thermostat, etc. Then I milled the head from 10.0:1 to about 11.0:1 sCR and cut three grooves per chamber:
It has been a complete success. The engine now sounds and behaves like an inline-six of larger displacement. Oil and plugs remain clean. Never overheats under abuse, radiator fan is now unemployed. Can lug it at 2000 rpm uphill and pulls without hesitation, car is SUPERB now in hill climbing. Fuel consumption improved about a 15%.
I own another Calibra with a 223 bhp DOHC 4V turbo engine which will also receive grooves next summer.
Many thanks to Mr. Somender Singh and to Mr. Randy Naquin (Automotive Breath).
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