i have a 1971 model 1200 coupe and am getting my A12 reconditioned, nothing great.... reconditioning to original, but i want to invest in twin 40 carby's.

i also plan to get low RPM street spec extractors...

are all 40ml carby's from different companies the same in regards to performance and fitting?

i keep seeing 40's from different companies with DCOE, DHLA and carby's with numbers next to the model like 34/35 etc etc.... what do they mean?

what 40's would best suit my plans?

and what else would i need to get them working?



sorry i'm a joob to old school motors as i've always had EFI....

thanks

DCOEs are weber sidedraught carbs - in 40 and 45dcoe. That refers to their throttle diameter in mm. That doesn't determine their flow - the venturi section does. WEbers have removable/swappable venturis (called 'chokes' in weberspeak, but not to be confused with teh choke mechanism for starting), so you can tailor their size/flow to suit a particular engine size/rpm range They are basically the ones you want. 40dcoes would be plenty for a mild a12, and you'd maybe get to a point of needing 45dcoes for higher revving a14-a15s.

DHLA is the model designation for sidedraught dellortos. they are basically the same in principle (and function) as the webers. Parts are a little bit harder to get for them, and generally most racers stick with the webers. Same deal though 40 and 45 dhla.

There's all sorts of downdraught webers - IDAs in particular. Generally not used on inline 4s - though they do have their place on boxer or flat engines where the intake ports are completely vertical - so they are good on performance vw engines, some alfa boxer engines, and a few ferraris and the like with flat 12 engines.

Then there is the more 'meat and potatoes' weber carbs - the 32/36 dgv (the numers refer to sizing of the primary and secondary barrels in this case) - and ther is a dgav, dgf (I thnk) - basically in that case teh letters after the numbers indicate if it had a manual or auto choke, whether the throttle linkage was on one side or the other.. The 32/36 weber isn't a bad carb, but I'd argue that if you were going to upgrade the output and want to stay normally aspirated, then twin 40 dcoe webers would be without a doubt the ones making the most power. If the budget didn't stretch that far, then an aftermarket manifold and twin 1 1/2" SUs would be worth a look (similar to the factory GX setup but since it's not the 'genuine' setup it is doable for a hell of a lot less money than originals go for)

Probably the most honest advice would be to really work out the budget. Whilst webers are 'the go' they aren't cheap, and for the money, you could instead acquire an a-15 and do that up instead - with a set of twin SUs - that'd outpower and out-torque an a12 with webers for sure.

Obviously then you'd really want to look at getting the head ported (and for that matter which head to start with) and a cam selection so it all worked together harmoniously.

All to often IMO our little datsun engines are over carbed. Upgrading to twin sidedraughts on there own will not gain a massive power increase. I can understand that you would desire twin 40's on your A12 as there do look fantastic bolted up to most engines.
In your own words you stated that your A12 is essentially going to be a std reconditioned motor, saying that [especially if you are on a tight budget] I would be very tempted to fit a DGV-5A series downdraught.[the variants are DGEV,electric choke and DGAV, water temp based choke]. Thes carbs can be found at the wreckers and or on most car forums for sale.
If you really have your mind set on a sidedraught, then IMO I would really really consider fitting a single sideddraught weber. There are manifolds availible and when match with a warm street cam would be a real goer. Also keep in mind that the DGV type carbs are a asynchronous in operation and are good for the economy side of motoring. the DCOE carbs are a synchronous type [both barrels open at the same time].

My vote goes for the DGV, but would happily fit a single sidedraught for a bit more performace [and aesthetics].

best of luck with it.

cheers

Yes I agree - twin side draft webers are over kill on a standard 1200, you will not be using them to their full potential and you will find it harder to keep them tuned right and it will be expensive to set up. One thing you need to be careful of is that you can actually loose power by over-fueling your engine. The other sidedraft used is the twin 1-1/2" SU, but again that is overkill, but probably cheaper and easier then the webers.

The DGV is a great set up - I have one on an A14 and it gives good performance and great economy. I am looking at the DGV with a nice set of headers for a standard 1200 that I have! I think that is all you need.

I dont think standard round ports would even flow enough to get much benefit from twins, too restrictive for high rpm so definitely get porting done along with a cam if u have your heart set on twin sideys, otherwise as they said a single will do the job. its only 1200cc after all.