I got a weber 28/36 twin barrel carb, will this be an upgrade to the hitachi dcg306? i'm looking for a bit more performance, i have already done a branch and 57mm free flow exaust but still not all there performance

another question, i got it with 2x coversion plates, one has one big oval hole and the other has two seperate holes, which will be better to use as the engine is dead standard

Will it be an upgrade?
You will get:
* Worse part-throttle performance. Worse fuel economy
* Better medium and full-throttle performance
If you are prepared to keep the revs up more than normal, you'll love the 32/36.

Your engine has a branch/extractor/header and 2.25" exhaust, I wouldn't call that stock. Those parts are good for high-revving performance. The 32/36 will help with that.

I would use the 2-hole adapter, but it probably won't make a difference.

Usually the reasoning behind multi-holed spacers under a carb are for applications where the carb size is borderline too big, and it helps increase the signal strength and hence ability of the carb to meter fuel with lower air flow.

In your case, the carb isn't even gettng close to that sort of size so the open holed spacer is probably the go. It's a tough call without actually seeing it, as the way it transitions from downward flow to make hte turn toward the cylinders (vertical to horizontal flow, can be affected, and a smoother gentle radius will flow more. whether or not that flow gain will equal a power gain (I mean specifically from that radius, not the flow gain from this carb swap) is debatable, sometimes harsher edges can help fuel be re-introduced to the airflow that would otherwise puddle.

So ultimately the best option is to try both adapters and see which one runs better.

It also goes without saying that if the carb isn't setup with the jet/emulsion/air corrector combination to suit the engine, you can find yourself making less power and using mre fuel part throttle (usually just one of the two, but sometimes both). So plan ahead that it might take a little tweaking to get optimised.

the carb is not a 32/36 but a 28/36 and i sent it for jetting etc for the a14

28/32 should run pretty well -- better than the 32/36. The stock A14 carb is a 21/26.