SU carbs and RC40
Discussion
hi, my twin 1"1/4 SU's came yesterday but i am still unsure what to use as i do have a single 1"1/2 aswell. the engine is a fast road/race 998 with a kent 286 cam and straight cut gears so which one would be the best to use for most performance? Also where is the best place to get hold of a single box RC40 system, everywhere i look there is only twin box systems available. or is there an alternative exhaust that pops and bangs with alot of noise along with high performance? Any information appreciated 
thanks
thanksTwin 1.25" SU's are good with the 276 & 286 cams, so long as the inlet manifold is cleaned up and matched to the head ports.
When fitting the twin-carb alloy manifold with the LCB you need to ensure that the centre pipe flange on the LCB clears the inlet by filing the top edge of the LCB to a 45 deg. angle. If you don't do this air will leak in. Also make sure the thickness of both the inlet and exhaust manifolds is the same and if necessary make up washers with a 'step' in to ensure it all tightens down tightly.
The ideal exhaust pipe diameter for a 998 is 1.625" internal. Mini Spares can sell you a single-box RC40 for a 998, but a 2-box is probably better for road use. By the way, an exhaust system should not 'pop or bang' but should run smoothly if the engine has been set-up properly.
With that cam you'll need the ability to run the engine to around 6600 rpm to get best power and to stay on-the-cam through the gears. There will be little power or torque below about 3300 rpm. I built a 998 engine with a 286 cam, lcb, twin-box Maniflow exhaust, twin 1.25's, a 295 head,eyc, and it gave 73 bhp at 6400 rpm.
It had a SC CR box and a 3.9:1 final drive.
When fitting the twin-carb alloy manifold with the LCB you need to ensure that the centre pipe flange on the LCB clears the inlet by filing the top edge of the LCB to a 45 deg. angle. If you don't do this air will leak in. Also make sure the thickness of both the inlet and exhaust manifolds is the same and if necessary make up washers with a 'step' in to ensure it all tightens down tightly.
The ideal exhaust pipe diameter for a 998 is 1.625" internal. Mini Spares can sell you a single-box RC40 for a 998, but a 2-box is probably better for road use. By the way, an exhaust system should not 'pop or bang' but should run smoothly if the engine has been set-up properly.
With that cam you'll need the ability to run the engine to around 6600 rpm to get best power and to stay on-the-cam through the gears. There will be little power or torque below about 3300 rpm. I built a 998 engine with a 286 cam, lcb, twin-box Maniflow exhaust, twin 1.25's, a 295 head,eyc, and it gave 73 bhp at 6400 rpm.
It had a SC CR box and a 3.9:1 final drive.
Gassing Station | Classic Minis | Top of Page | What's New | My Stuff