22 replies to this topic

[Cooperman]

+1 for the twins. Once set-up they are very good, especially at mid-range revs. Make sure you remove all the casting 'flash' inside the manifold and match the manifold to the carbs. The standard BMC alloy manifold is poor, but it can be improved greatly with some re-shaping of the tracts.

[oltonlad]

there you go, conformation from mr cooperman........you cant say fairer than that.............

[Easyrock]

Best order some linkages then :) just whilst we're on twins, my cars going off for paint in a few weeks so I was gonna take out the 998, whilst it's at the spray so and give it a quock checkover with new pumps etc would it be worth fitting twin hs2s to it? It's a completely standard engine at the moment

[oltonlad]

you can put the hs2's on a standard 998, you will get a bit more torque........................but it would have been even better if you had bought that cooper cam that ive got............

[Easyrock]

I was very tempted to buy that, but got offered a 266 from someone local, but, he then decided to keep it :/ not too bad though really because I wasn't actually looking for a cam for the 998, just thought it would match the twin hs2s and cooper manifold I've got haha

[Cooperman]

Twin HS2's on an otherwise standard 998 are really not worth the trouble. You have to fit the linkages, get a better ex. manifold to clear the alloy inlet (I think) and then get it on a rolling road to get the correct needles and settings. The standard head is the big limitation as well as the cam, so you might as well stick with the single and save all that work. If you had a 295 head and a 3-into-1 ex. manifold with a better exhaust system, then the twins would work better and with a better cam it would go very well indeed.

[Easyrock]

Ah ok, think i'll leave it for now then and just use them to build a pokey little 998 when I come to fitting the 1380

[Cooperman]

The 998 is such a rewarding engine when nicely improved. It will rev to 'high numbers' without getting harsh like a 1275.
With my grandson (Cooperkid) we built a 998 which was bored to 1061 cc (+0.060"), fitted a gas-flowed 12G295 with a C.R. of 10.2:1 and slightly larger inlet valves, an improved HS4 on a Howley alloy inlet, an early 3-into-1 ex. manifold with an RC40 exhaust system.
The cam, which 'Cooperkid' found in a box in my workshop, was an early 1275 Cooper 'S' 510.
We changed the distributor for an Aldon 'Yellow' and fitted duplex timing gears and a slightly lightened standard flywheel.
It gave just over 60 bhp bhp at 6000 rpm and was lovely to drive so long as it was revved. However, around town at lower revs it had nice manners and was not at all lumpy.