Discussion
i have tewo options for carbs on my fast road 998, i have a single 1.75" su and twin 1.25" su's however, which would be better for my engine? it has a 286 kent cam. i am also trying to upload some pictures of the engine rebuild but the it keeps saying "upload failed, unable to get image info, check that the file is a picture" i know the file is definatley a pic because i can see the thumbnail in the folder. anyone know how to sort this? thanks 
Personally I've always liked the twin 1.25 SU's, but I guess it's a matter of choice. A 1.75 on a really good inlet manifold will work well, but I grew up with the original Cooper which had twins.
With regard to the heater pipes, I never run them through any manifold as the inlet charge needs to be as cool as possible. The old Coopers and Cooper 'S's never had water heated manifolds and they do go well. The claim is that a water heated manifold helps on cold mornings. "If you like" as they say! Some induction systems even have cold-air boxes to cool the inlet mixture.
A really good spec for a 998 would be twin 1.25 SU's, a gas-flowed 295 head, a 3-into-1 exhaust manifold, a Kent 266 cam, a comp. ratio of about 10.3:1 and a custom distributor to suit. Maybe a slightly lightened flywheel and an RC40 or Maniflow exhaust system. That lot should give around 55 to 60 bhp or maybe slightly more if built very accurately.
With regard to the heater pipes, I never run them through any manifold as the inlet charge needs to be as cool as possible. The old Coopers and Cooper 'S's never had water heated manifolds and they do go well. The claim is that a water heated manifold helps on cold mornings. "If you like" as they say! Some induction systems even have cold-air boxes to cool the inlet mixture.
A really good spec for a 998 would be twin 1.25 SU's, a gas-flowed 295 head, a 3-into-1 exhaust manifold, a Kent 266 cam, a comp. ratio of about 10.3:1 and a custom distributor to suit. Maybe a slightly lightened flywheel and an RC40 or Maniflow exhaust system. That lot should give around 55 to 60 bhp or maybe slightly more if built very accurately.
Twins are great, but the problem is the poor standard twin-carb manifold. It can be improved by flowing and removing the sharp edges, but there was a twin-SU manifold which looked standard but was much better. It was stamped 'Torquemaster'. I have one, but I don't know where you might find one now. It's not the same as the one for the single SU's as sold by Mini Spares as the Torquemaster Inlet Manifold.
Edited by Cooperman on Wednesday 7th September 19:21
Just for your comparison, my 998 has a cleaned up 12G295 with rimflo exhaust valves and slightly larger penny inlet valves,mini sport mild road cam, 9.7:1 compression, cleaned up std 1 1/2 carb on a howley inlet manifold not connected to the heater pipe, std filter case with a larger inlet pipe and K&N, Mini spares 3 into 1 ex manifold and an RC 40, vac pipe removed from dissy. it showed 64 BHP on the rolling road last summer. hope this helps. Plank
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