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Finally time to ditch the carb?

Scatpack said:
Sounds like the people who went with efi/tbi don’t know how to tune a carb, better yet, drive a car with a carb..... :) (it a joke guys) 30,000 miles with the bee with Holley DP mechanical secondaries with no choke in three years, from -10 degrees to 90 degrees, up and down in valleys and hills, no problem????
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You are pretty much right on that.

Tuning a carb is a skill that must be learned. It is accomplished by turning bolts and changing numerous small parts and gaskets and leaks and fuel where it shouldnt be and on and on.

You must use the same basic rules of air and fuel ratios, but you make adjustments with a small hand held programer, which used to require a full on computer but not anymore, to achieve the changes you want to make in various tuning parameters. Including tuning the ignition.

I am talking myself more and more in to switch over guys.
 
I have no issue with fuel injection except the price. For the system plus tank, sending unit, in tank pump vs. Carb and electric pump the price is significant for a 2 mpg gain. Cold start and fuel boil is an issue unless you run a choke and electric pump. Maybe some day.
 
Paul_G said:
True. I have an a/f gauge installed and use it to dial in the carb. Trying to get a clean smooth idle, lean cruise, richer light acceleration, and full throttle safely rich is almost impossible. Trial and error right? A mess is what I end up with. 2 of those goals are atainable, but all of them not so much with a carb.
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what carb are you using?
 
The 670 works better than the 750. The 670 is factory tuned lean. Upsizing the priming jets a few sizes worked well. Took care of the lean surge at cruise. Got it to cruise in 14 range, but then a little rich at WOT dropping in to low 11 range. Blocking the PVCR a slight bit killed some of the richness at WOT. Got it working fairly well. It was lacking power at WOT compared to the 750 at WOT.

So I started tweaking on the 750. If I get it to cruise in the 14 range, WOT is lean in the 13 range. this was a bitch, get WOT in the low 12's, cruises too rich in the 12's, get it to cruise in the 14 range, then fighting stumbles and hesitation problems. On acceleration it is sluggish in the 13 range till the PV opens, upsize the primaries a little, cruises rich, WOT in the 11's. I am tired of fighting this carb. If I tune it for WOT the engine pulls hard, If I tune it to cruise , kills WOT performance. If I tune it where everything is acceptable, none of it is exceptional.
 
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The EFI versus Carb can be debated with valid points on both sides, but the EFI wins when you consider one item; ETHANOL. It is not impossible that a day will come where E15, or even E25 will be government mandated. For the next two years we might be safe, but depending on the powers to be, it is not unrealistic to have to deal with higher blends of ethanol.

Personally, I can't wait to get EFI someday. I understand the 'driving a classic' opinions, but to me EFI is a "component" improvement much like the old classic cars getting a 6V to 12V conversion, points to HEI, etc, etc.
 
Or disc brakes over drums. Ethanol is a valid point. The more ethanol that goes in the fuel the lower the BTU content, but it maintains the octane rating. Requires more fuel to be consumed. Easily adjustable with FI. Jet changes required on a carb.
 
The cost of the EFI looks better as the power level increases. On a mild 300-400 HP engine the carbs (600-750 cfm) are very affordable and you don't need a real expensive fuel pump/supply system. When you start pricing the larger 900+ cfm carbs, and high volume fuel pumps/supply systems, then there is not much difference in cost. Also, with the carb are the costs of tuning parts and gaskets.
 
Valid points here. But what ever happened to the hobby of maintaining an old car? Where an old muscle car actually took skills to maintain and drive the darn thing? Take an average joe who have never started a car with a carb and bet he won’t be able to start it without help. That’s why I got into old cars, it’s a skill that’s learned. I don’t mind shitty *** ride or 8 mpg or have to use 91 non oxy gas or rebuild the carb every year after it sits dead for 6 months. What are you EFI guys gonna do next? Put tpms on your rims so you don’t have to check air in your tires? Back up camaras so you don’t have to use mirrors? Because that’s the easy way to do things. Yes EFI is easier but anybody can run an EFI and drive an EFI.
 
That's a good point. Really, most of my old cars still have carbs, but part of the adventure is trying something new too, and the EFI is on the Convertible which I plan to take on long distance trips. That is why I an setting it up more like a pro touring car, EFI, OD trans, disc brakes, and A/C.
 
I get the whole EFI point with reliability. Don’t get me wrong, I did carry an extra fuel pump and a carb kit when I drove a 1,000 miles road trip in a weekend in the bee. Nothing did ever happen with the carb but you never know
 
Paul_G said:
The 670 works better than the 750. The 670 is factory tuned lean. Upsizing the priming jets a few sizes worked well. Took care of the lean surge at cruise. Got it to cruise in 14 range, but then a little rich at WOT dropping in to low 11 range. Blocking the PVCR a slight bit killed some of the richness at WOT. Got it working fairly well. It was lacking power at WOT compared to the 750 at WOT.

So I started tweaking on the 750. If I get it to cruise in the 14 range, WOT is lean in the 13 range. this was a bitch, get WOT in the low 12's, cruises too rich in the 12's, get it to cruise in the 14 range, then fighting stumbles and hesitation problems. On acceleration it is sluggish in the 13 range till the PV opens, upsize the primaries a little, cruises rich, WOT in the 11's. I am tired of fighting this carb. If I tune it for WOT the engine pulls hard, If I tune it to cruise , kills WOT performance. If I tune it where everything is acceptable, none of it is exceptional.
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some of this is typical holley. I think to be able to totally tune a holley the PVCR needs screw in jets and some up scale carbs have that. screw in air bleeds help tuning. I think the metering rods in AFB's make all this simpler. we drive our newer cars with ease and wish our older cars would do the same. if one thinks about the complexity of new car fuel management it really isn't possible to totally duplicate it on our dinosaurs. I don't know if it's possible to find a throttle body FI that can learn. I think some kind of direct port with no fuel in a throttle body might be best but then again a total package of fuel/ignition management would be best. i'd think the FI would require a fuel return line but carbs work well with that too. i'm not at the point to where I feel FI is best for what i'm doing and cost plus the paraphernalia makes me a little shy of it. it would be nice for those for folks who successfully done FI start a thread laying out what they have, combos, do's and don'ts.
 
Maintaining the originality of these old cars is important. Some need to be preserved for future generations. Then there are those of us that want to use these cars, want them to be reliable, stop well, go well, turn well. Getting a 40 to 50 year old car to perform more like a modern car is a challenge. Some of us enjoy that challenge. My 72 is on it's way to doing that.
 
Paul_G said:
Yep. Hot dry summer air from 105 to 115 degrees, A/C running, engine running at max temps in 200 to 210 range. To mild winter air in the 50 to 70 degree range, engine running cool at 180 degrees. Carb doesnt like to run smooth with those variances unless mixture adjusted and idle speed reset, etc.

I remember an old episode of Goldberg's Bull Run when the dodge charger had to do a stunt running through a parking garage, (in Vegas maybe?), and stalled out. They claimed the altitude and temperature change caused the carb problem. I can relate to that.
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That was Team Charger. Mike Musto. Just a heat-soaked big Block. Altitude and temperature contribute as my car runs the worst in Reno in Summer. When watching the episode, I could relate. Spacers, wraps, etc have reduced the symptoms. The critical time is an engine at or above normal operating range shut off for more than 10, but less than 30 minutes. Heat soak. I'm keeping the 850 Mighty Demon.
 
Great discussion. The fact is, once you're making 500-700 HP; the cost is nearly identical to run TBI EFI. There is no way on Earth I would pay $800 for a mechanical carburetor (Holley Ultra XP for example) when I can purchase a complete EFI kit for $1,000 with a true warranty. Yes, MPFI EFI systems offer many advantages over TBI EFI; for triple the investment.

For those discounting EFI, they must not own a wideband gauge. Watch how absolutely terrible a carburetor is metering fuel at anything other than WOT / IDLE / LIGHT CRUISE. A carburetor is lost during any sort of transition, which is a majority of our time driving in the city. You can see how quickly, even 1/16" of an inch of pedal travel during cruise can dramatically effect in the air-to-fuel ratio. In high school, my father and I removed the factory EFI system (and A/C) on my 91 5.0ltr lx coupe and installed a carburetor, i'm die hard as they come; everything in the name of cost/performance.

I've ran a carburetor on everything since, even on my blow-through turbo setup. Tuning them became second nature, but they take too much time away from actually driving (frustrated as we often solve one problem with a tune and then that solution upsets another aspect); they offer no true advantage over TBI EFI other than they cost a few hundred less. There are other things I would rather spend my time doing than working on a carburetor for no other reason than to waste time in the garage, JMHO.
 
Sweet5ltr said:
Great discussion. The fact is, once you're making 500-700 HP; the cost is nearly identical to run TBI EFI. There is no way on Earth I would pay $800 for a mechanical carburetor (Holley Ultra XP for example) when I can purchase a complete EFI kit for $1,000 with a true warranty. Yes, MPFI EFI systems offer many advantages over TBI EFI; for triple the investment.

For those discounting EFI, they must not own a wideband gauge. Watch how absolutely terrible a carburetor is metering fuel at anything other than WOT / IDLE / LIGHT CRUISE. A carburetor is lost during any sort of transition, which is a majority of our time driving in the city. You can see how quickly, even 1/16" of an inch of pedal travel during cruise can dramatically effect in the air-to-fuel ratio. In high school, my father and I removed the factory EFI system (and A/C) on my 91 5.0ltr lx coupe and installed a carburetor, i'm die hard as they come; everything in the name of cost/performance.

I've ran a carburetor on everything since, even on my blow-through turbo setup. Tuning them became second nature, but they take too much time away from actually driving (frustrated as we often solve one problem with a tune and then that solution upsets another aspect); they offer no true advantage over TBI EFI other than they cost a few hundred less. There are other things I would rather spend my time doing than working on a carburetor for no other reason than to waste time in the garage, JMHO.
Click to expand...

You are correct in everything you said. The wide band o2 is the key. You will see plain as day what is happening. A carb just can not meter efficiently through out the rpm range with varying loads. It just cant, which is why the OE's dont use them anymore.
 
Well, I'm coming out of left field here, so here goes! The main reason I'm looking into this Injection
setup is to be able to use E-85 in my BB. Alcohol has always been a superrior fuel to gasoline
because it makes lots of HP, runs cooler, and now that we have an "easy" way to meter it,
I think I like it! Hope it gets better and better, and hell yeah, I think there will be a day coming
when gasoline as we know it goes away. The more accurately we are able to supply an engine
with air and fuel throughout the RPM range and at varying loads, the more efficient the engine
becomes and we can squeeze out all of the performance.
 
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