guys i jut wanna ask i plan to use the dcoe 40 on my datto but with all internal stock will it be ok ?? i need some advice ..

Depends on what motor it is, where the DCOE's came from, you might need to chokes them more and alter jetting, you will need to change the advance curve in the distributor to run without vacuum advance.

You should get DCOEs to run well on any motor, stock or not, whether you have money left in your pocket afterwards is another story.

if im using a15 ?? everything stock including the cam

I would recommend getting a mild cam only if you can afford to get it dialed in and distributor recurved to match, find someone with a dyno who can work on webers and have a chat to them. A15 with a cam and webers would go nicely.

Just my two cents worth on the issue if you are keeping the motor stock why would you want to add twin sidies?????????I agree with white sedan get a cam and maybe polish your inlets and raise compression a little.I have been told that by adding the sidies to a stock motor you would over fuel the engine get bore wash and end up with a worn and tired motor in the end.Maybe if you do what white sedan said you may just get away with it.

Agreed, i used a stock sub, but with head work and a cam to spec. this would be what those Webers want.. and u aswell probably ^_^

I used twin 40DHLA DelLorettos on my race car (pictured in the avvy) on a stock 1200 bottom end. Had a mild cam and had cut the head to about 10:1 C:R. It ran pretty well although didn't idle too well. Idled at about 1500 and pulled well to 8800. Dyno'd once and it seems to me it had about 90HP at the wheels.

If you are sporting the 15 it should be a bit better. I would recommend, as other have, a bit of a cam and cut the head to bring the C:R up.

so in other wprd will it reliable or not ?? how about downdraft weber ..

It will be reliable if they are in good gondition and you have them tuned to your engine properly.
Seconhand carbs $500+. Good dyno tune and carb parts $500+

The problem with webbers/Delortos is unless they have been set up for a very similar engine you can spend hundreds on changing chokes, jets, emulsion tubes etc.

Downdraft weber, same problems.