what are people results with all these carbs on a 998?
Depends entirely on wht else has been done to the 998… Bog standard - then stick with a single HIF38. Full race (Cooper S head and 544/649 cam) - twin HS4s on a ‘weber like’ manifold work very well!
i bought a 12g295 but might give it a clean up and sell it on its unskimmed i think i’ll go down the 12g940 route because i’ll get a bit more power what do you think?
piper 270 cam
aldon ayp100 dizzy
balanced, crossdrilled and wedged crank
work on the con rods
bored out +40
steel flywheel and backplate
orange clutch
what carbs?
and what should i do to the 12g295 if it is kept?
looking for around 70+ bhp
??
HIF 38 will be fine for your spec, not sure if that spec will make 70+ Hp either!
You should get around 70 with that spec if it’s all set up accurately and the 295 head is gas flowed properly. You will need to set the compression ratio at c. 10.3:1 or slightly higher and, ideally, fit slightly larger inlet valves.
As for carbs, to get 70 you’ll need either an HS4 or HIF38 on a really good alloy inlet manifold, such as a Howley, or a pair of HS2’s on a good manifold. When I say good manifold, I mean one that has been cleaned up and matched to carb and head ports. The exhaust will be important and for a 998 it seems to be generally accepted that a 3-into 1 as fitted to the original Cooper 998 is best with a good silencer box (R40, Maniflow) and a 1.625" internal diameter exhaust pipe.
As your engine is to be lightened and balanced, you ould probably pull a slightly better cam such as a 286, although it would then be very ‘lumpy’ low down and would need a low diff such as a 3.44. It would, however, then give over 70 bhp. It’s all a compromise, especially with the lovely 998 engine.
do you think putting a 12g940 on it and a if i bought a kent 286 cam would help maybe bore it out to +60?
> HIF 38 will be fine for your spec, not sure if that spec will make 70+ Hp either!
we can only hope…
YES to the 940 head - big valve version if you can find one, but don’t worry about boring out any more than you need to. And yes - the 544 type cam works brilliantly in that engine - I found a 649 was a step too far, tried it, and reverted to the 544. Excellent! But for that sort of power (~ 80 bhp ??) - you want the twin HS4s on a really good inlet manifold - ie NOT the standard alloy one !
with the 12g940 does it move alot of the power up the rev range?
Its not the head itself that moves power up the rev range but the cam, by the way that head works better at higher revs than low/mid range.
About carbs, my money is on the HIF44.
For real power my money is on the twin 1.5’s.
To fit a 12G940 with a cam like a 544 or a 286 I think you’ll need to pocket the block to achieve valve clearance.
The 544 was a great cam back in the 60’s and I used one in several rally cars. Personally I think it’s ‘had-its-day’ a bit and the later cams from Kent and Piper are better these days. However, if you have one in your pile of parts, then it’s still good to use for a road car.
yh ive bought a piper 270 so its a bit of a bugger that a 286 would be better yh i’ll hopefully end up with a 12g940 then i should be able to make the power easier
You’ll be pushed to get 70 bhp with that cam, although it should be a good driveable engine. If you fit a 286 to a 998 it is very ‘cammy’ and won’t pull much below about 3200 rpm if set up for max power, and the max power will only come at around 6400 rpm. Below about 5500 rpm the 270 cam will perform better than the 286 in a 998.
Boring to +0.080" to give 1061 c is a help is are the fitting of Hastings flat-top pistons.
yh what would your guess be of the bhp i’ll get on my spec and how driveable do you think the engine would be.
i’d use it on roads mainly and take it on a few track days if i feel like it.
