11 replies to this topic

[Jacko5]

Morning all,

I am after some technical advise please. Basically i am doing a bit of engine upgradings for a bit more driving fun. I have had all the machining work done. Parts are all collected for the main build. The engine spec is as follows:

- 1275 bottom end with std pistons as the bore wear was 'f' all.
- Polished crank
- Centre main strap machined in. (probably overkill, but who knows what the future holds?)
- 12g940 head which I have polised and ported with some expert guidance, 3 angle seats.
- Std valves which have been relieved and 3 angle seats.
- Sw5 camshaft with matched double valve springs.
- Lightweight vernier duplex timing kit.
- High flow oil pump

The next thing i need to purchase is the twin carb setup that i want. So . . . . . . . Which carbs would be best for this kind of setup? Twin HS2 or HS4?

I think i could really go with either, but i am concerned that the twin HS4s could well be over the top. This is only going to be a road car. Not being built for the track. Although it may go round combe at some point.

Any body who has opinions or similar setups, i would gladly receive your comments and input.

Thanks for looking.

[jackmason]

Morning all,

I am after some technical advise please. Basically i am doing a bit of engine upgradings for a bit more driving fun. I have had all the machining work done. Parts are all collected for the main build. The engine spec is as follows:

- 1275 bottom end with std pistons as the bore wear was 'f' all.
- Polished crank
- Centre main strap machined in. (probably overkill, but who knows what the future holds?)
- 12g940 head which I have polised and ported with some expert guidance, 3 angle seats.
- Std valves which have been relieved and 3 angle seats.
- Sw5 camshaft with matched double valve springs.
- Lightweight vernier duplex timing kit.
- High flow oil pump

The next thing i need to purchase is the twin carb setup that i want. So . . . . . . . Which carbs would be best for this kind of setup? Twin HS2 or HS4?

I think i could really go with either, but i am concerned that the twin HS4s could well be over the top. This is only going to be a road car. Not being built for the track. Although it may go round combe at some point.

Any body who has opinions or similar setups, i would gladly receive your comments and input.

Thanks for looking.

I'm also kind of interested in what people have to say. I had a set of twin HS2's on my 1380 and it run pretty good, but they did need tuning and i ended up using a HIFF44 instead.

[petehuws]

I've been down this route before running twin HS2's which were good, but in all honesty after the eye candy of twin SU's had worn off on me I reverted back to a single HIF44 which was definitely better all around. The HIF44 is perfect upto about 85-90bhp, if you're not breaking that sort of power I'd recommend just the HIF44.

[Jacko5]

Thats interesting. I have got a very good Hif 44. But i really want the twin carb eye candy going on. I have considered sticking with the 44 but its just not the look im wanting.

[Vipernoir]

HS4s.
Without stirring up old arguments, twin carbs are just better - as long as they are in good condition.

[Jacko5]

The carbs are going to be brand new. So condition is not an issue. Or shouldn't be. I have seen the arguements for and against twinning. But i'm set on a twin setup, so that's that.

So HS4s wouldn't be overkill in your opinion then?? Would HS2s be a shortfall? I'm assuming that it is just a case of the 1'' 1/2s giving a greater volume of fuel/air mix over the 1" 1/4s, so more bang for buck. Surprisingly the difference in price for twin HS2s to 4s is literally less than a tenner.

[Jacko5]

Sorry, make that less than £20

[iwatkins]

If you are set on a twin setup, then a pair of HS4s is how I would go.

Just ensure they will fit with cone filters fitted between the engine and bulkhead, taking into account any gaskets, spacers, abutment plates and inlet manifold you choose to use. Also ensure you have somewhere to attach the throttle and choke return springs.

Cheers

Ian

[KernowCooper]

The HIF 44 is good for engines in excess of 100bhp and Vizards says 110+bhp is not a problem so its got plenty of scope and is way up on a pair of HS2s HS4s would be good if you do intend doing future upgrades

[pr3nna88]

Ive got a set of twin hs4s. But currently running a single hs4 on a 1275 cooper engine. Would the twins be overkill on a standard engine? Planning on upgrading the engine in the future just wondering if it was worth fitting them now or after?

[petehuws]

Nothing is really an overkill if you really want it but you must respect the balance of components. If you were to add twin HS4's then you should also be thinking of having an equally compatible LCB and wider bored exhaust, you can actually decrease performance by fitting large carbs and then not giving them enough bore to port & exhaust.

[pr3nna88]

Yeah there hs4s. Its already got an lcb and rc40 centre exit exhaust. That right?