Can anybody please inform me about the 48 IDF weber carbs and which IDF weber carb provides more top performance?

48 mm carbs are huge. You'd better have an absolute monster motor to support those carbs. We need more information about the motor they're going on before making any predictions.

Here is some European thinking on carburator size.

One of the fastest ways to create an engine with a less than friendly usable RPM range is to over carb it.. The TIV is a velocity engine and doesn't need massive amounts of intake volume to make it's best power.
we make 200HP from less than 2.3 liters and 9.5:1 CR with only a 44mm IDF carburetor with a stock 36mm venturi.

These engines have a TON of usable power and don't just perform well on the dyno, they have an RPM range thats usable from 2-6.5K RPM and thats the key to making a fast car.

I don't use a 48mm carb till we exceed 2.7 liters, but this is with engines that feature my design thats greatly different from other tuners.
the bottom line is big carbs perform best on big engines and unless you have the budget for a big engine the big carbs will just be hard to tune and make usable power at an RPM that the engine isn't generally operated at. That means their use is virtually worthless on anything of "sane" displacement.

I had a buddy of mine recommend that if I put 44's on the 2056 I would be better off. I told him the motor seems to be running pretty darn good with 40's , and it just seems to me 44's on a 2056 would be a little overkill. It did make me curious as to what difference the motor would have with 44's on it. Am I correct, would 44's on a 2056 be too much carb?

I had 40MMs on my 2056 when I built it . My Son wanted to see how it would perform with 44's. We installed EMPI's 44's and he says he can feel the improvement at high RPM. I know it is running rich but it is cold in Atlanta and I don't want to rejet until it gets warmer. The flat spot at about 3000 RPM is gone with the EMPIs , that could be the rich mixture. Oh! at the Dyno it does show rich now. I'll have a better responce whenit gets warmer.

You'll always be happier with carbs that are too small than you ever will with carbs that are too large. Just because they'll bolt up and they're larger doesn't mean that it's a good thing to do.
Some 22" wheels with spinners might bolt up, they're large too, but that's not a good idea either.

Does seem like a huge carb, I thought the Delorto 45's I had were huge...even though I'll probably never put them on my car.

I'd trust what Jake says about carb-size and performance, he's tried a various number of combos and actually has a dyno to test them.

90% of your driving is done in the low to mid RPM range. A smaller carb will have better throttle response and drivability in these ranges. A larger carb will provide better high RPM performance but it's at the expense of throttle response and drivability. I'd stick with the smaller carb almost every time unless I was building a drag car.

sww914,
Whats wrong with 22's, DAWG...

Yee hawww a couple o buck boards!

Back OT, you are getting good advice, don't over carburate your engine.

Drive the car.
Define upper end for yourself. At our age its probably lower than what your son feels. You can put in a rev limiting rotor to save the motor from your son...I did and he never knew.

Big valves and big carbs will only kick in from 4500-5500 rpm and then your valves start to float...unless you have stiffer valve springs, lighter valves, etc etc.
Track car, living at those RPM's for 20 minutes...you bet.
Street car that stops and goes...never.

I have tried both...the 40mm carb, properly jetted is really a nice match for these motors under 2.2 liter...that seems to be about the limit.

Intake air speed in the lower range is terrible with big valves and big carbs...or one of those alone..even worse. Then the air/fuel mixture stands a good chance of deatomizing with the fuel returning to a liquid..then fouled plugs are the result.

Rich

These guys would not lead you wrong. Keep your 40's and have fun.

I'm in the market for some new carbs. I now have on some Euro bastard child 40 idf models that came with the car and my mechanic is trying his best to get them to work for me a while longer.

He tells me after my engine rebuild that if I do get some new carbs, to look for some nice Delorto's. If not than he recommends I up to the 44's. The engine as it is now is a 2056 with some aggressive CB Performance cams and springs and a set of KB pistons.

My guess is that a pair of new (Spanish) 40's would be fine. Could the 44's work well? Conventional wisdom say's NO NEED.

If anyone has an old useless set of 48mm webers they're throwing out I'll take them off your hands for you.

me too...

This thread seems closely-related to a question I asked a day or two ago.
HIJACK

Me too. Or 44 IDF's, 48 IDA's, 45 DRLA's or any size DHLA's. I have no particular conviction, will help you get rid of any of these models.