I haven't got a Rapier but I run a Rapier engine in my Commer Auto-Sleeper camper and I though some might find this of interest. A recent head gasket failure gave me the opportunity to try out some Vizard modifications to the combustion chambers, something I've fancied doing for ages. Being an alloy head it's surprisingly easy to do with basic tools, I do have an air fed die grinder but the air tank on my compressor just doesn't have the capacity to maintain a decent speed - and it's noisy. So armed with a normal drill with one decent burr, a Dremmel with a flexible extension and a variety of sanding and polishing heads I set to work.
I think I see the problem
Looks like cylinders 1 and 2 had had a good steaming
First I made a template from the Vizard instructions
Then coated the surface of the head with a marker pen and scribed the outline of the gasket and template
After removing most of the material with the drill and burr (about 20 minutes on each chamber) I was left with this
Cleaned out the ports, didn't go for a mirror finish but removed enough to take out casting marks and edges especially around the valve throats.
After a good final polish of the chambers. a skim, valve lap and final assembly the seal was tested with paraffin and all was well
Back on the engine and re-united with my rather amazing custom inlet manifold and SU HIF44 conversion.
It's always been a good engine and performed well in the van but this mod seems to have given a bit more mid range pep and pulling from around fifty to seventy mph in overdrive top is smooth and fuss free. Given the weight of the vehicle the engine is pushing along it does very well so in a normal car it should be quite impressive.
Hi Mike and thanks for the reply. The idea is to improve the engine's 'breathing' by creating a smoother gas flow and un-shrouding the valves making it more efficient and so releasing extra power. I'm certainly no expert on the subject but have a keen interest and have put a few performance mods in place on my camper and Mini Cooper. This is the article I followed which explains things far better than I could and the results speak for themselves.
Very neat job, you must be very brave! We used to drive Commer ( and later Dodge) vans on Britsh Telecom (BT) so I know you must be doubly brave to drive one at 70mph! Although I'm sure yours is miles better than our overloaded ones! Happy camping. Jerry Shaw
Thanks Jerry. It's capable of a lot more too but I tend to stick to about 65 motorway cruising speed and with decent dampers up front and the rear Armstrongs filled with SAE 50 to stiffen it up a bit it's surprisingly stable. The big bonus is the torque the engine produces, those long M'way climbs can be done in OD top with little fuss and Shap holds no fear Well over 30 mpg isn't bad either at those speeds.