Which Carb?

hi i have a 998 but dont want to be restricted for power too much by the choice of carb
ive been told a hif38 is on its limit at 65bhp
and a hif44 isa bit big and can be naff at low speeds
is there any carbs that are inbetween the two what are twin hs2's like?

Depends whats the spec of the small bore, the standard HS4 works along most of his tuning specs, exepct the hotter race engines.
HIf38 is perfect up to 65/70 bhp, same as twin HS2s, but they drink more fuel compared to the HIF, which, when well tuned, give almost the same performance. Over 65 bhp you can use the Hif44 to improve performace, which is a must have if your engine has 70 or more bhp.

12g295 head ported polished etc, alloy inlet manifold, bored out +40,wedged,bladed and cross drilled crank,steel flywheel and backplate,piper 270 cam, balanced con rods duplex timing chain. aldon 100ayp yellow dizzy. rc40 1.75" exhaust system which carb for this?

Edited by D1k1m4y, 10 March 2010 - 10:50 PM.

The only things which effet the carb choice are head, valve sizes, compression ratio, exhaust and cam.
From your spec it appears that an HS4 or HIF38 would do the job, so long as your inlet manifold is a good one. you can 'gas-flow' the carb a bit to improve flow capability or go for an HS6 or HIF44.
I had a 1061 engined car with a 295, 510 cam, 10.3:1 CR, 3-branch manifold and Howley alloy inlet and it gave 66 bhp at 6000 rpm. I really don't think a bigger carb would have given any more and at mid-range a larger carb could have slowed the input charge and lost a bit of power/torque.
Personally, I like the original Cooper 998 twin HS2's so long as the manifold is gas-flowed and the carbs are well set-up on a rolling road.

Edited by Cooperman, 10 March 2010 - 11:04 PM.

so a hif 38 gas flowed would do the job i was looking for around 70bhp

So long as everything else is up to the job that carb will be fine. The critical things to get to 70 bhp will be the standard of build quality and accuracy of assembly, especially the cam timing and the matching of head to manifolds. It vwill all need to be done well as you are scratching for every bhp with a 998.
I built a 1967 Cooper 998 a few years ago as a rally car with a 286 cam, a well-flowed head, lightened flywheel, twin 1.25 SU's also gas-flowed, 10.4:1 CR, all balanced, etc and it gave 72 bhp at the flywheel at 6500 rpm. It was a bit 'lumpy' to drive on the road and we soon changed the engine to a 970 Cooper 'S' lump with 1.5" carbs which then gave 84 bhp at 6800 rpm.

would a hs4 rebuilt and gas flowed be up to the job do you think?
i have loads of them hanging about.

Edited by D1k1m4y, 11 March 2010 - 07:48 PM.