Tuning your Suzuki consists of increasing the compression ratio, enlarging the intake ports and larger in- and exhaust valves. You can also remove some of the camshaft spline on one end, so you can alter the camshaft timing a few degrees!
By increasing the compression ratio to about 9.5 you will get much(!) better throttle responce, more power and more torque. The downside is that the engine will vibrate slightly more when idling. Even with a compression ratio of 9.5:1 it was impossible to get the engine to "pink" or get it to the point where detonation or pre-ignition occurs. No matter where you put the ignition timing. (Tested on unleaded 95 and BPR6ES spark plugs). Because the head sits lower on the block, you get different, read retarded, valve timing! Tuning the valvetiming is pretty difficult, I filed one side of the camshaft spline, so you can alter the camshaft timing a few degrees!
General guideline to engine tuning: "The 80% Rule". Which means that the intake port area should be max. 80% of the intake valve area, the exhaust valve area should be about 80% of the intake valve area and the exhaust port area should be 80% of exhaust valve area!
In a lot of engines the 80% is already applied. so you can just use the exhaust valve to check the intake port area. It should be a tight fit. In case of the F8B engine is the exhaust valve area is 76,3% of the intake valve area.Have had the head skimmed by 0.85mm to increase the compression ratio to about 9.5 instead of 8.7 to 1. Skimming the head by 0.85mm will just skim the squich area (the bump on the bottom left of the combustion chamber). Do not forget install the BPR6ES sparkplugs otherwise your engine starts pinging at around 105kmh. (Glow ignition!)
Bore the intake port to a nice round 28mm in diameter. Tip: You can use the exhaust valve to measure the diameter, and at the same time to see if the port is nicely round! You can also use 3 28mm wood drills to get the size right.
Note: No carbon deposits on valve or intake port. So in original configuration there are extremly high gas speeds! Smooth the edges in the combustion chamber next to the intake and exhaust valve seat. This will increase torque significantly. Polishing the combustion chamber prevents carbon buildup
Remove all the roughness in the valve seal, You will have to make sure the diameter of the intake manifold is enlarged to about 27mm. An easy way of doing this is buying a few 28mm stealbrushes that fit in a drill. For the curved channels you have to use an extension (5mm tap end) that fits through the vacuum hole on the left. Tip: You can use the exhaust valve to see if the diameter is OK.
