40 vs 44, Quick question Options

[schreiber]

I'm looking at a nice set of Weber 44 IDF's. Will 44's fit on my 1.7? From what I've read, 40 IDF is usually used on 1.7 and 1.8, while 44's are used on 2.0's. Any insight?

I've been told this should work fine; I thought I'd see if the group had anything to add...



For good measure, my current *crappy* setup:

[VaccaRabite]

You want dual 40s.
unless you are going larger then stock in the near future, you don't want dual 44s.

The can be made to work, but you will have a much finer line tuning them, and will probably use way more gas then needed.

Zach

[Todd Enlund]

Your gonna want 40s on a 1.7... 44s are kinda big even on a 2.0 unless you make some other changes.

If you're interested, I have a set of Italian 40s that I'd consider trading for a set of 44s... I'm building a 2270 with a few performance mods... not radical, but definitely would benefit from 44s.

[dr914@autoatlanta.com]

You want dual 40s.
unless you are going larger then stock in the near future, you don't want dual 44s.

The can be made to work, but you will have a much finer line tuning them, and will probably use way more gas then needed.

Zach

Zach is dead on! 40s for the street 44s for the high rpm 914 raced at the track

[schreiber]

Your gonna want 40s on a 1.7... 44s are kinda big even on a 2.0 unless you make some other changes.

What 'other changes' am I looking at?

[VaccaRabite]

An engine is just a big air pump. The bigger the carb, the more air the engine will suck down.

Larger carbs can pump larger air, but the engine has to be properly tuned to use all that air and fuel, or the benefit is lost. If you put too big a carb (like 44s) on a small motor (like a stock 1.7), even if you use the smallest venturii made for the 44 (32mm?) you will still be sucking more air then the engine can process through most of the power band.

What you will see, is that from 0 to 3K rpm you have little to no power. From 3K to redline, the engine will SCREAM and make LOTS of power. The reason being that below a certain RPM, the engine can't process the air/fuel it is being given.

This is why George from AA said that the 44 would be good on a track car. The engine will always be at WOT (Wide Open Throttle), it can process all the air, and make good power.

But, driving to the grocery store or just around the block at WOT is not a good idea, at least in the long term. (IMG:style_emoticons/default/wink.gif) Therefor, you want to limit the amount of air going into the engine to be efficient at lower RPMs. Ergo, smaller carburators.

Zach

[VaccaRabite]

Your gonna want 40s on a 1.7... 44s are kinda big even on a 2.0 unless you make some other changes.

What 'other changes' am I looking at?

For a 1.7, changes you might make to want a bigger carb...
A turbocharger. (IMG:style_emoticons/default/chowtime.gif)
5 pound flywheel
Race cam.
Dual spark heads with bigger ports.
A full roll cage
Track Tires.
no-heat headers
A truck and trailer to tow the car to the track and back (IMG:style_emoticons/default/poke.gif)

Even on my 2056, with 44s necked down as small as they will go, the car still wants to make power in the upper end of the rev range.
Zach

[SirAndy]

I ran 44 IDFs on my hot 2056. I had to choke them down to 32mm venturis to get rid of the off idle flat spot.

I can't imagine getting them to work right on a stock 1.7L ...
(IMG:style_emoticons/default/huh.gif) Andy

[So.Cal.914]

Your gonna want 40s on a 1.7... 44s are kinda big even on a 2.0 unless you make some other changes.

What 'other changes' am I looking at?

Put a set of 96mm P&C's which will increase your displacement to 1911cc. Run the 40's and you WILL have a fun car.

[r_towle]

I ran 44 IDFs on my hot 2056. I had to choke them down to 32mm venturis to get rid of the off idle flat spot.

I can't imagine getting them to work right on a stock 1.7L ...
(IMG:style_emoticons/default/huh.gif) Andy

Even with them choked down, you probably still ran very rich around town, and got about 20mpg.

IMHO 36mm dual carbs are great on the 1.7 and 1.8.
40mm are to big, but will work.
40mm dual carbs on a 2.0 liter runs nice and its tunable...

If you change the camshaft and clean up the heads,,,,slightly larger valves, then 40mm dual carbs on a 2.0 liter are perfect.

If you increase the compression ration to around 11:1 or higher, and get a very aggresive camshaft, plus increase the valve sizes...then you could use 44mm carbs on a 2.0 liter.
The last example (Like King George said) is a motor that has no power below 3500 rpms....all the power is from 3500-7500 rpm...not a street car.

I think (dont quote me) Jake does not use 44mm carbs until 2.4 liters or more.
I had a 2.4 race motor running 40mm carbs...scca rules.

Rich

[schreiber]

Wow thanks for the input guys! I went ahead and purchased the 44 IDFs (I figure I'd rather barter with those than with nothing)... So now I guess I'm testing the water- anybody want to swap for a good set of 40's? I think I'd prefer Webers cause of their good reputation, but will be happy with any 40's that are in really good condition.

Also, I tried getting in touch with the PO of my 914. If I recall, I THINK he told me that he increased displacement to 1911cc when he did a rebuild a couple years back. I still want to find out if he used a more aggressive cam.

Hopefully I'm on my way to a better 914 (IMG:style_emoticons/default/smile.gif)

[Jake Raby]

Some combos of 2056cc engines like 44s... I use them on every engine between a 2056-2615 for full street usage.

The key is going down 2 mm on the venturis with a small engine to enhance drive-ability and throttle response. Thios works much better than a larger vent in a smaller carb and is easier to tune.

A stock 2 liter or smaller engine will run best with 40s