8 replies to this topic

[TAYLOR30]

As the title states I basically want to know what it the best carb or carbs are to run for a cooper s 12g295 head. Twin hs2, hif44, twin hs4 I really don't know.

To help you out here is a bit about the engine specs.
998cc engine from 1988
Lightened flywheel
Full maniflow system including 3into1 manifold
Currently running single hs4 with k&n
Going to be putting the 12g295 head on with the new carb

[miniman24]

If the engine internals are standard (i.e. if its just the head, flywheel and exhaust that are uprated) then I would go with a nicely rebuilt set of HS2's - Im running a modified head and RC40 system on an otherwise standard 998 with twin HS2's on Speedwell inlet manifolds and it goes well, not even tuned properly yet either.

[jaydee]

You need to recurve the dizzy first.

Keep your HS4 just carefully choice the correct needle for the new head.

A pair of twin hs2s would give a better throttle response when tuned right, if on standard camshaft dont bother.

[TAYLOR30]

When you say recurve the dizzy what do you actually mean?

[blacktulip]

Your standard HS4 carb is good enough for a tuned 998  Have you calculated what compression ratio (CR) you want to run? Getting the CR correct is so important with the 12G295 head as the standard 12G295 head chamber size is around 28cc per chamber. At 28cc the compression ratio will be way too low for any improvement (probably lose you power). So you will need to skim the head at some point to achieve the required CR but then you may want to look into a better camshaft. Unless you fit a decent road cam i.e (piper 270, Kent MD266 or MG Metro) i would seriously think about what you are doing as you may end up being very dissapointed with the end result  you will definitely need flat top pistons unless you have these already?

 

Have you got any other mods planned for your engine?

Edited by blacktulip, 08 June 2015 - 12:09 PM.

[jaydee]

The standard ignition curve might not deliver the optimal timing, well worth spending money on a custom dizzy and a custom carb needle instead of upgrading the carb to twin or hif carbs.

[TAYLOR30]

Im picking the head up from vmaxscart on friday after they have done valve seats and skimmed to get the compression ratio right. Any suggestions on what to buy jaydee?

[blacktulip]

cool, i have a Vmax2 head on my 1301cc and it performs well.

 

where are you taking it for rolling road?

[coopdog]

I put a 28/36 weber on mine and it sounded awesome