What >> percentage << of performance ( horsepower, responsiveness, fuel mileage, cold weather starts ) decrease should one expect to wind up with if one replaces a perfectly good fuel injection system on a perfectly running 1.7 for example without changing the cam or distributor? How much would a centrifugal type distributor improve on overall performance?

I am not arguing that a dual carb set up with proper cam and distributor or a fuel injection system is not vastly superior - I am just wondering if anyone can define what vastly superior is in ballpark numbers.

Jim

Its more a driveability factor. The single carb can be tuned to run great a WOT but getting there smoothly and with all the hp is the problem or at cruise or idle. Not to mention the icing of the runners..

Having all the at their best is what FI is all about, accurate fuel at all three.

The stock dizzy is a centrifical dizzy witha vacuum advance/retard on it. If its in good working order just install electronic ignition on it. Going to a type 1 009 limits your total advance to 17 degrees so you fight with that big hole at off idle.

very cool and informative reply - thanks - jim

From what I remember timing my '76 914, you start with 7 degrees advance anyway so you get a total of 24 degrees?

I am not putting out fires with gasoline here, i am just stating my personal exsposer
end "not carb vs FI debate starter" disclaimer

We put a set of 34 icts on Shanes 1.7 liter almost two years ago and he has been happier than a pig in poop ever since! I might goes as far as to say it is the peppiest 1.7 I have ever drivin!

I have single progressive that I just to just move cars from here to there, Not work the headaches IMHO...

Some 30 years ago when my 2.0 EFI left me stranded on several occasions, I installed a single barrel Ford carburetor until I got some Weber duals. The carb was too big for the motor, but never left me stranded which was a huge relief at the time. It drove exactly as one would expect from an over-carb'd motor. Poor off-idle and low speed response. Ran fine at cruise, and probably faster at WOT than the EFI. FWIW.

Andys

What headaches did you experience Dino?

Hmmm
Poor idle, and bad milage or good idle and bad at speed! The biggest headache was getting the damn thing centered so the flow was equal! One bank would run then the other! On the plus side, rebuild kits are at your FLAPS...
Add the ice, and it is just a PITA.

So rather than futz with it, I bought a whole car with Fuel Injection. The single is on Ugmo so I dont have to push it. Once I start gathering part for that car, Samba here comes the carb!!

I have yet to install my single carb. I'll run that until I figure out D-Jet or can afford dual carbs. You know carbs are made to be jetted. There is no reason why a single carb should be a horrible experience. Unless others have some info particular to the 914 application.

Not trying to hijack your thread Jim, just trying to get some hard facts about problems with single carb that could be remedied to make it a better experience.

Long runners make the mix run lean, due to the fuel dropping out of the mixture before making it to heads....

I know my head temps ran REAL hot, I could hear it while running....

Ended up dropping a valve on that engine...Just be careful.

*ahem* if you would LIKE a single carb system, I have one for you with fuel pump.

b

location, location, location

single carb has air AND fuel that must travel from the middle of the engine to intake valves, not only is it a long distance, but there is a tight corner that the air/fuel mixture must go around once it gets near the head...what happens is that you get fuel seperation due to the some of the fuel dropping out of the atomization mixture and now clinging/driping on the intake tubes. This affects the fuel-air mixture being delivered to the intake valves.

Also, the reason for poor off idle or acceleration response is due to the carb being so far away from the intake valves, you get a "lag" between the time you hit the pedal to the time the fuel makes it's way to the heads.

With dual carbs, you are right there, right now...sure the intake manifold might get a little "wetting" but not enough to change the air-fuel mixture.

The single carbs do work, but there are much better solutions. It seems that 90% of all single carb installs are done by half-ass mechanics looking for a cheap and easy solution....hey, why should a shop care, they are not the ones that have to drive the car

Thanks for all the info. Now I see the short comings. I have all I need except the fuel pump BD.

no problem....heck, the single carb is tempting, only reason my car is not running is due to the fuel injection problems (aftermarket FI which I screwed up the install...doh !!! )

[quote name='Thack' date='Jun 23 2006, 01:03 PM' post='710735']
You know carbs are made to be jetted. There is no reason why a single carb should be a horrible experience. Unless others have some info particular to the 914 application.

The single carb on a type 1 uses a heating tube to arrest the ice. I know that carbs are made to be jetted, but you take a POS carb and a cam for FI add in a ton of time and money, sure you can MAKE it work, but why would you?

futzing

Futzing or "futzing around" is unstructured, playful, often experimental interaction between a human being and a computer, product, or any technology, sometimes but not always with a productive purpose in mind. Futzing can be pure play, learning by trying, or an attempt to achieve breakthrough insights.

Quote "I know that carbs are made to be jetted, but you take a POS carb and a cam for FI add in a ton of time and money, sure you can MAKE it work, but why would you?"

Because the FI is 30 years old and any one component can strand you on the side of the road. Not what I want. Rather have less performance and more reliability until I can afford a better solution.

location, location, location

single carb has air AND fuel that must travel from the middle of the engine to intake valves, not only is it a long distance, but there is a tight corner that the air/fuel mixture must go around once it gets near the head...what happens is that you get fuel seperation due to the some of the fuel dropping out of the atomization mixture and now clinging/driping on the intake tubes. This affects the fuel-air mixture being delivered to the intake valves.

Also, the reason for poor off idle or acceleration response is due to the carb being so far away from the intake valves, you get a "lag" between the time you hit the pedal to the time the fuel makes it's way to the heads.

With dual carbs, you are right there, right now...sure the intake manifold might get a little "wetting" but not enough to change the air-fuel mixture.

The single carbs do work, but there are much better solutions. It seems that 90% of all single carb installs are done by half-ass mechanics looking for a cheap and easy solution....hey, why should a shop care, they are not the ones that have to drive the car
[/quote]

Tell this to drag racers that run tunnel ram manifolds, and you might get a different perspective.

Back durring my salt flat days, we ran a Corvair with a single 4 barrel carb with 4 long tubes that ran to some 140 heads. That little sucker would really set you back in the seat when you stabbed the throttle; and I mean right now!

This is not to say the dual carb setup isn't perhaps better, it's just that a single carb on long tubes can be very effective as well. In the case of the 914, the air plenum floor is lower than the lowest part of the runners (at least on a '73 2.0L). I will speculate that this *could* lead to some fuel puddling, but I never saw this on my temporary single carb setup.

Andys

I'm thinking of a way to keep up the velocity in the intake tubes. Also inducing a vorticie near the bend to keep the fuel drop out at a minimum.

That is a fair statement, I was getting a little snippy, sorry. you would be better served selling the single and getting a used set of ICTs for the itrerum... At idle in under five min I had ice on the runners, and I mean scrape and make a snow cone ice...

I will go back under my rock now

last time I looked at the tunnel ram I had for my Ford 429, there was not many 135° corners for the a/f mixture to go around

It's possible that the intake manifold/plenum on your Corvair might be been designed better???? Also, aren't the intake plane on the heads closer to horizontal?

Ice? I'm in Houston so ice is not a big deal even in the winter. You didn't come off as snippy. I welcome all input as it can only be useful. I tried to buy dual ict carbs here but wasn't quick enough. Are ICT the same as PICT? They look complicated, are they?

does it get humid in Houston?? there is more to carb icing than just the ambient temperature.....

"does it get humid in Houston?? there is more to carb icing than just the ambient temperature....."

Humid? Yes, but with temps in the 90's now I have not seen icing. Is it the fact the fuel evaporates and atomizes taking energy (heat) out of the air?

[/quote]

last time I looked at the tunnel ram I had for my Ford 429, there was not many 135° corners for the a/f mixture to go around

It's possible that the intake manifold/plenum on your Corvair might be been designed better???? Also, aren't the intake plane on the heads closer to horizontal?
[/quote]

The Corvair (both 110 and 140 heads) had a cast-in-head intake manifold designed to accomodate either one or two single barrel down draft carbs per head. Within, were some fairly abrupt changes in direction. Not a very performance oriented design in either case, to say the least. The four barrel plenum style aftermarket manifold had intake tubes that simply attached to the original carb mounting flages.

Andys

Whenever I install a single (32/36) carb I use the metal intake gaskets. This will allow heat to transfer to the manifold and keep the air/fuel from separating. I also drill out the idle jet to .065 or .070.

Thanks everyone for the healthy exchange of views and experiences : )

Jim

ambient temps have very little to do with carbs icing up ...

Andy

I am un sure, I have only used the ICTs and they are sooper simple. Single barrel, check with Carbs Unlimited or webercarb.com

Carbs icing up is due to thermal dynamics. One end of the circuit is red hot therefore the other end freezes. This is the reason why some intakes have exhaust runing through the manifold just to keep it warm on type1 single carb setups. I have had no problem with mine freezing up as of yet and the throttle and idel is great; with my progressive. The only problem I have is the high idel is not as smooth as I would like it to be at about 3.5K. Do you all know if its because of the FI cam? Hey, for about 650$, there is a set of brand new 40IDFs available at an online vender so I will probably get them soon.

In 10 years I have never had the FI crap out on me or left me by the side of the road.

I have had 3 pertonix crap out and be towed home, had a throttle cable break and be towed home, had the clutch cable break and drive home crashing the gears, had the Alt crap out and drive home on the battery until the FI stopped work due to low voltage and be towed home..... never has the FI broke so I couldn't drive. I have blown a MPS but I still could drive it althought running reaally rich. I have never nor can I see a ECU dying or a injector dying (still have 3 more to run on) so this whole BS that 30 yr old stuff leaving by the side of the road is BS.

Now I did have a single carb on my 72 bus which in the winter/fall/spring you drove it would freeze up in about 3 minutes of driving. ICE would form over the runners and stop the motor dead. Sit by the side of the road stuck (these are brand new parts not 30 yr old FI parts) and I had to wait until the ice melted, then you could drive to where ever. I tried ducting hot air and all that, nothing helped so I HATE single carbs.

Duals, FI are what is proven to work and not leave you by the side of the road.

The Type 4 conversions that are used on aircraft are prohibited from using any carb or tbi that distributes fuel from a single central location.
They must use direct injection or carbs mounted on the head.
I always figure the guys making the rules for aircraft applications want to work towards the reliable side of things...
Dylan

For a constant speed motor on a airplane TB's mounted to the heads is nice.

The central TB with runners on a car motor is cheaper, easier to tune and has great throttle response. TB's on the head is nice but a small headache if over come produces good results. (See motorcycles)

single carbs offer no advantages over duals or even stock FI so why go there.

Bleyseng there are other things like wiring, fuel pump, CHT sensor (when they fail the car stops) vacuum lines. Some you can easily fix others you can't detect.
I'm not saying FI isn't superior. I'm saying until I learn D-jet or can afford duals, a single carb would simplify things. I've talked to a few people that only complain about performance ont he single carb.