Carburetor

As a self-described newbie, you are doing what you should, i.e., gathering info and researching here and (hopefully) other sources.  One word of caution: many engine builders are sensitive about accepting advice from an owner who got his knowledge from "online friends".  

I suggest that your research should include which builder will work best for your needs, then discuss options with him.  There is nothing wrong with asking questions.  That's how we all learn.  How you apply that learned knowledge is another type of skill that sometimes comes from experience.  Best of luck as you move forward.  

 Yeah, what Jim said above! Some engine (and transaxle) builders really don't like being contradicted. THAT said-

34 mm venturis in 40 mm carbs should allow a 2276 to go to 6,000 rpm with good power- it's been done before-                     https://www.thesamba.com/vw/fo...rder=asc&start=0

40 mm Dellortos will accept 34 mm venturis readily with no problems. There are some models of 40 mm Weber IDF's, though, that that have a smaller diameter at the carburetor top and 32's are the limit with these. There are IDF's with the larger inner diameter tops (I've been told the same as the 44 IDF?) that you can put 34 mm venturis in. I'm of the understanding that the 40 IDF's with the smaller tops can be machined out to the larger size (although don't quote me on that). I don't know about HPMX's or anything else.

I believe 40 mm carbs on an engine like this will be really close to (or even at) their limit- I've never heard of an engine this large making power to 6500 rpm with these carbs. Doesn't mean it can't- I just don't think I've ever heard or read about it. The great thing about using carbs this well matched to the engine size/power output- instant throttle response throughout the rpm range and the best mileage possible! Al

PS- @Michael Balastrieri- Who do you have lined up to build the engine? What heads are going on it? Do you know what compression will be set at? Cam/rockers? exhaust?

There are those who think a 1776 needs 48 IDAs. There are those who put a single progressive on a 2332. None of this is a black-art, there are formulas for sizing pretty much anything once a set of values are established. 

The thing is... having a "2276" doesn't tell you very much. There are no shortage of guys willing to throw a stroker crank and some 94s in an otherwise super-mild engine and sell it at a price-point. Displacement is only one variable in making power.

Think of it like this (at least for now): an engine is an air pump. The more air that gets moved through the pump, the more power it's going to make. The displacement of the pump has an effect on capacity. But if you are trying to move air through a straw, you'll move a lot less than through a 3/4" pipe, no matter how much swept area is in the cylinders.

Everybody will tell you that the power is in the heads-- because the heads determine how much (and how efficiently) air gets moved. The cam and the heads are interrelated, because the cam controls how long and how much the valves are open. This matters at least as much as the swept capacity of an engine.

Your builder has an idea what he wants to use for heads and a cam. If these parts are mild, he's specing 40s because generally, smaller carbs offer more drivability than big ones. If the engine doesn't need 45s (because of the heads and cam), then putting them on won't help, and will probably hurt.

... or maybe he's an idiot. That's the thing about this hobby-- there's no shortage of thieves and charlatans who prey on guys who know just enough to be really dangerous. Assuming you have a guy who is trustworthy, most VW engine guys fall into 2 camps: drag racers and octogenarian guys who rebuild 1300 cc single-ports. They are going to have different recommendations for sure. Neither are going to build the engine you want, unless they are really listening to you.

If they are listening, and you trust them, then the best advice comes from Jim Kelly. Unless you're ready to assume 100% responsibility for how the entire thing turns out, you've got to pick a guy, and go with what he thinks.

Above all, disabuse yourself of any notion that you can choose more wisely and frugally than most other people, and end up with 10 lbs in in your sack when you paid for 5. In this hobby, you might not always get what you pay for, but you'll always pay for what you get.

Always.

Stan, you make some excellent points, as always!                                                                   Specifically, @Stan Galat wrote- " Assuming you have a guy who is trustworthy, most VW engine guys fall into 2 camps: drag racers and octogenarian guys who rebuild 1300 cc single-ports. They are going to have different recommendations for sure. Neither are going to build the engine you want, unless they are really listening to you."

I have friends with dune buggies; we go out in the mountains for 2-3 days, 3 weekends a summer. My son and I drive our FJ Cruiser and someone else has a 4 door Rubicon (37's- it's quite tricked out) but most of the other guys are driving fiberglass buggies, there usually being 6, 8 or more cars in the pack.

A friend of a friend in the group was building a buggy 3 or 4 years ago to be able to join in the fun and wanted more power than a stock carbed 1776/1835/1915 offered, so I get a phone call out of the blue (we hadn't yet met) with him asking about bigger engine combinations- what works and what doesn't. I already knew that one of the guys (a very good friend) who builds the odd engine and keeps a number of these buggies in good repair has a prettty good recipe for these cars and wanted to build for him a stock 69mm stroke, stock 34-3 Solex and manifold, stock dual port heads, Engle W100 cam and 1½" header, but Neil wanted more, so (having already discussed this with Gerry, the engine builder, as combinations aren't always his thing) I suggested stroking it slightly (74 or 78 mm crank), having the stock heads ported and machining the venturi in the carburetor a little bigger. In a lightweight buggy (or anything really) it would be a killer lower rpm, high torque combo and not cost a huge pile of cash to build.

I put him in touch with a local guy who ports heads (very well respected in the VW performance world) and that's when things started to go south. Darren (a drag racer- damn them!) tells him (without really understanding the type of vehicle it's going in and the terrain we drive- he's a street car guy- 'nuff said) with over 2 liters he's leaving power on the table, it should be revving to 6,000 rpm with power, have big valve heads, more cam and more carburetion. The problem- I've put enough time in these cars to know there's not enough suspension travel with stock VW parts to control that much power, but what do I know- I'm not the big name engine builder/head porter/drag racer. 

End result- the engine ended up being built by someone else (surprisingly, not Darren), cost probably 50? 75? 100%? (Neil was rather closed lip about the final cost) more than he originally wanted to spend (the builder didn't like the parts he'd already collected and insisted on using his parts, which he of course made money selling to him), he can't use the power/rpm at will without it becoming dangerous (that not enough suspension travel thing I mentioned earlier) and on longer trips (we sometimes cover 120 or miles in a day) has to carry extra gas so he gets back.

And yeah, I've also met a couple local builders that refuse to do anything for you if the parts aren't made by the sainted Elves of Wolfsburg (it's stock or nothin'- how boring is that???)- they're a royal pain in the a** as well!

I know, we're off topic AGAIN! My apologies for the rant/boring story, but when I read what Stan wrote... I know, Al, it's time to go back to bed for a little bit...

35 years or so ago I opened an Impala's hood to check the oil and found a 454 under there with a 2-barrel rochester on top. I believe those were like 450 or 500 cfm.

So be generous & call it 70 CFM per liter.

If it had a quadrajet it would be 650 or so but might have got as much as 800 cfm. So, 100-ish cfm per liter, max. 

Weber 40s flow a little more than 200 cfm. In a 2.3 liter engine that's 92 cfm per liter. 

The 44s are close to 300 cfm. That's 130 per liter. 

In the muscle car arena, most people use way bigger carbs than necessary which are also way bigger than ideal.

Common misconception is that more CFMs are better.  That is not always the case!

edsnova posted:

35 years or so ago I opened an Impala's hood to check the oil and found a 454 under there with a 2-barrel rochester on top. I believe those were like 450 or 500 cfm.

So be generous & call it 70 CFM per liter.

If it had a quadrajet it would be 650 or so but might have got as much as 800 cfm. So, 100-ish cfm per liter, max. 

Weber 40s flow a little more than 200 cfm. In a 2.3 liter engine that's 92 cfm per liter. 

The 44s are close to 300 cfm. That's 130 per liter. 

Well... that seems like we are overcarbureted, but there are some things that didn't make their way into the calculations. The most important is the difference in the type of manifolds being used on each engine.

I don't ever recall seeing a 2 bbl big-block, but my memory is poor and for the sake of discussion, I'll play.

But, for reference: a factory LS6 454 had an 800 cfm carb.

The Rochester 2 bbl carb (and indeed, the Quardajet as well) on that Chevelle's 454 was doubtless sitting on two-plane plenum manifold (where half of the carb feeds half the cylinders) Hick-town shop-heads in my part of the world ran single-plane manifolds, so that the entire CFM rating of the carb fed 2 cylinders at a time, but the effect is the same-- half the total CFM of the carb feeds each cylinder. The carb is always feeding and flowing, because one cylinder is always on the intake stroke.

The Webers/Dellortos we use are on individual runners (one throat per cylinder). Each throat is flowing 200 cfm, but it's only doing it 1/4 of the time.

On the plenum manifold-- the banks were divided in half, so each half of the carb fed 4 cylinders, none of which were on the intake stroke at the same time. Half of the carb that flowed 450- 500 cfm (225- 250 cfm) was devoted to one cylinder at a time (since none of the others were on the intake stroke). On a 454, each cylinder displaced 56.75 cubic inches (or about 930 cc).

Our hypothetical 40 IDF (or DLRA) flows 200-ish cfm per venturi, devoted to about 525 cc (on a 2110).

So, the lazy 2 bbl 454 (nobody wanted, or had, a 2 bbl big-block back in the day) was actually about 270 cfm/l (given that half the carb was feeding one cylinder at a time) and the hi-performance VW is being provided about 381 cfm/l by the 40s (given that each venturi is devoted to an individual cylinder, and cannot cross-feed another one).

That's only 1.4x as much carburation on the VW, as compared to a 2 bbl big-block. If we were looking at an engine that even approached the hp/l of the hi-po VW in the V8, we'd see that it was going to take a LOT more carb-- something like 1.5x, which would be a Holly 750 (or the factory 800 cfm carb on the LS6).

What the VW world does to make power may have been arrived at by trial and error, but there are mathematical reasons it works. Science-y stuff nobody but me cares about (until they do).

And once again, Stan takes the boys to school with those darn incontrovertible facts.

Don't ever stop. I learn something from you just about every time you type.

Thanks, Man!

Dude.

I hope some day to build a custom engine from scratch has for my speedster.  I think I can get enough info from all you guys !!😂