I agree with what you said and the decision will ultimately come down to what I choose, but being a new guy to all this and knowing just enough to get in trouble these forums give me a lot of different things to think about. A lot I would not have ever considered. I know we all have our opinions and preferences, but reading here gives me new questions to ask and gives me new leads read about what I am researching. IT'S ALL GOOD! And a good way to start learning. Thanks for the input.

 

I actually have a 1980 302 in it now with a new 600 cfm Holley Avenger on it. Engine is stock and just not what I want. I ran across a heck of a deal on a 1993 302 HO with very few miles on it with the EFI and all still on it. Engine starts and runs like a new one. Mods so far are prototype Legend Gear and Transmission 3.92 rear, Wilwood 12" discs on front and back, Wilwood dual master cylinder, RYR flywheel, Spec clutch and plate, T-5 trans but will be switching to a Keisler 6 speed in the near future, 17" AR 500 wheels, BF Goodrich Super Sport tires, 8" on front 9" on rear. Car was taken down to the metal and rebuild wit all new parts. Project now is this engine swap and upgrade. I definately want a new cam and heads and have no idea which to use for EFI. I had my carb package picked out until I started questioning taking the EFI off now I am back to square one.

 

I agree 100%. I will never have the expertise to tune anything that complicated. If I don't want to go custom and want to keep my stock intake, if possible, any cam or head suggestions? Thanks.

 

I have been very satisfied with my Retroteck Powerjection 3 and wish I wouldve done this year ago before I spent $2000 on a carb/fuel system. I had a issue a few days ago because i swithchde laptops and it erased my file for the tuning. I reloaded a flash drive to my new laptop, programmed it in less then a minute and drove it.DONE.If I change cams or heads or whatever, even raise or lower my boost, its nothing more a few clicks of the mouse and its retuned.

 

My point was to try and make the most valid comparison I can. Comparing what one car ran at 1 track in 1 part of the country, to another car at an entirely different track in an entirely different part of the country is simply not a valid comparison. Like I said, stock 3V's are a know 13.60-13.70 car with solid 60's in fair weather. At the track I've run at (Famoso) I've never seen a stock 3V, even on 2.0 60's driven by people who actually know how to drive, go any faster than 14's. Most typical drivers in stock 3V's out there go 14.50's. Folks throughout California go there because other tracks are shutting down, and they all say the same thing, they run slower out there than many other tracks. It's just how it is.

And my point was not to compare which car was faster, but to show that despite the design limitations of my engine(pushrod head, no variable cam timing), a carbureted engine of similar size and produce similar power. Even without accounting for weather(which results in an unfair comparison) the difference in mph can easily be attributed to variable cam timing and a better cylinder head. How much of it do you really think is the carburetor?

And as far as me not "proving" anything, you either didn't read what I posted earlier, or you didn't understand it. Either way stating it again is pointless. Like I said, EFI will compensate completely for atmospheric changes, while a carb can only do so marginally. But the actual changes in fueling aren't usually enough to make much, if any, power difference. A street engine at 12.8:1 vs 13.3:1 isn't going to make more than 1-2% more power. In a street car that won't matter. Carbs have disadvantages, one being the lack of ability to precisely compensate for atmospheric changes. But that's usually more than made up for in atomization and emulsion advantages.

 

Are you now talking about a 4.6 3V or the 4V 5.0?I have a 3V, it does run mid 13's and with a tune and gears it runs 12's. A 5.0 4V will run 12's easily. Im well aware of Famoso and go out there once in a while and its one of the quicker tracks in the area.Im not sure the people you talked to said they run slower because I know me and my friends have ran quicker there then Irwindale or Fontana which we go to weekly.

Either way, its based your opinon, im still waiting to see what a dead on tuned $1500 carb looks like.

 

Partially true. The manifold portion is correct. But the part about carbs you got wrong. The fuel doesn't "dribble out at essentially 0 pressure."

Consider the basics of carb operation....airflow through the venturi drops pressure below atmospheric, right? So the fuel is actually pushed through the system at a pressure that is the gradient of the atmospheric pressure vs booster pressure. Given that the booster won't reach total vacuum, and there is also booster pressure signal loss from the air bleeds, you're looking at something like 10-12psi of pressure, perhaps as high as 13.5psi, pushing fuel through the metering system. So the fuel doesn't dribble out, it's pushed out under pressure, albeit low pressure.

But there's even more to it than that. Booster design greatly influences atomization. The shape and design of the booster, and where the fuel comes out in the booster, determines how the high air velocity distributes fuel as it leaves the booster. There are also sheering forces at play which pull the fuel apart and distribute it into the airstream. And that's all before the fuel even gets past the throttle blades of the base plate. Some booster designs are better at this than others.

Older booster designs like on the older Holleys for example, that have the bar going over the booster, were quite bad at this. The bar design impeded airflow in the booster, resulting in signal loss and disruptions in airflow that prevented good fuel distribution. The fuel came out of the bar in the center of the booster, and the idea was to try and centralize fuel delivery to evenly dist. it, but it didn't work as intended. The most common now is the downleg booster. The fuel comes right out of a single hole in the side of the booster where it comes from the main well. Ironically it dists. fuel into the center better than the old bar style did. The airflow velocity and sheering forces pull the fuel apart quite well and dist. into the airstream quite quickly. Going a step further, some carbs run a "stepped" downleg, where a countersunk cut is made in the bottom of the booster up to where it intrudes partially into the hole the fuel comes out of. This step actually generates a very strong turbulence as the airflow passes by it and it creates huge sheering forces that help to pull the fuel apart even more for better atomization.

Then there is the newest design(and quickly becoming popular), the annular. Ford was smart when they used annulars on their carbs, and there was a very good reason for it. With an annular, the booster actually has a "ring" or fuel channel INSIDE the booster body. The fuel comes from the main well through the booster arm and fills up in the ring around the booster, and is then distributed out into the airstream from a series of holes around the entire perimeter of the booster. This means that the fuel is most evenly dist. into the airstream around the entire booster. More holes that are smaller means smaller fuel droplets that are more evenly spread around and more rapidly atomize. Annulars are large though, and actually restrict airflow. It helps them to atomize better since the booster velocity is higher, BUT it can be a breathing restriction if the carb is sized on the small side. Typically though the loss of flow is offset by the power gains from a better atomized mix.

The Quick Fuel I run actually has very nice annular boosters. It's a stepped annular design, where the inside of the booster has a "step" that is just at the top of the discharge holes. So in addition to the high airflow velocity, you have a huge sheering force where the fuel discharges. The atomization on those boosters is insane actually. Without even being at WOT just free revving the engine, the fuel cone they spray is impressive. It's basically a massive aerosolized mist of a fuel cone that occupies the entire venturi. You can't even see the throttle blades when they're running full tilt, so it's certainly atomizing.

http://www.youtube.com/watch?v=XREjAZpf1kE This is a video of Demon testing a carb with downlegs, to give you an idea. Notice the fuel cone is relatively narrow. The larger annulars generate a wider fuel cone with more angle, so that it encompasses the entire venturi. The fuel cone itself in an annular also generates airflow restriction.

THEN.....there's also the matter of the emulsion system. That's more a matter for an entire other thread, as it gets into various other things such as fluid surface tension, fluid vaporization points, 2 phase flow etc. But, to simplify it, one of the things the emulsion system in a carb does(as a side benefit really) is to reduce the surface tension and vaporization points of the fuel. It actually breaks the fuel up into extremely tiny droplets, and turns the fuel into a foamy, frothy mixture while still inside the carb. The foamy, frothy fuel mix is much closer to it's vaporization point, is much easier to lift(helps raise it up the main fuel well), reduces the inertia so the fuel moves/distributes more easily, delivers fuel from the booster already in a partially atomized state, and requires less thermal energy to get to a highly combustible state.

The lack of emulsion in EFI means it NEEDS high pressure and specially shaped nozzles to deliver the fuel in a form that can easily be mixed/vaporized and combusted. Carbs deliver the fuel in an emulsified frothy form, EFI delivers the fuel in an aeroslized liquid form.

But, that gets into one of the drawbacks of the carburetor. While EFI uses a constant high pressure and nozzle shape to aerosolize the fuel, a carb relies in air velocity in the venturi. That means that at lower throttle positions and lower rpm, where air velocity is lower....boosters become less efficient. And while you can get a carb to deliver a reasonably well mixed fuel supply under part throttle such that the car runs fine and gets decent mileage....it simply doesn't have the precision and efficiency needed to come anywhere close to generating low emissions. Carburetors are most efficient at WOT.

http://www.pro-system.com/scoop92102.html This is an older article from Pro Systems(who build carbs for NHRA, IHRA, NASCAR etc) breifly discussing the differences between carbs and EFI.

 

I'm talking about both. Every time I've been out there running the 4.6 3V's are way off their pace, everyone is. Most of the time at Famoso the temp is high, or the humidity is high, or both(at least at the test n tunes in the summer). And track prep isn't always good on test n tune nights. Every time I've been there stock 4.6 3V's can't get out of the 14's, even on 2.0 60's with good driving. Most of the time at that track, cars run a half second off their pace. So that means if guys are posting basement 13's in a 2011 and are a half second off....that would make it around a mid 12's car, which we both know is the case.

If you want to know what carbs can really do, read this. I've posted it on other threads before.

http://www.epi-eng.com/piston_engine..._cup_to_f1.htm

It's an honest comparison of the 2 mostly highly developed race engines in their respective class, 1 carb'd(NASCAR Cup) and the other EFI(Formula 1). One thing he discusses is the fact that the Cup engine is just a few % down on efficiency from what the F1 engine is doing....but the Cup engine has crippling engine restrictions, and even has to run a carb that's about 20-25% smaller than what the engine needs. When you factor in all the restrictions on the Cup engine, it's clear that having a carburetor isn't costing it performance.

Granted, that's way the hell beyond $1,500 carburetor performance, but it's a comparison of the most highly developed EFI engine to the most highly developed carb'd engine. It's the peak of development for each system.

 

If they are getting a 2.0 60ft, that is NOT good driving. I cut consistant 1.78-1.82 60 fts in my 06 convertible on 20's.

Either way, everybody has their own side

So no pic of this $1500 carb on a 302 still?You do relaize that sounds rediculous right?

 

2.0 60's on street tires at a track that sucks for launching on street tires? Even if you think 2.0 60's suck, a stock 3V with a 2.0 60' should still be showing high 13's with a mediocre driver.

And the carb itself is not $1,500, I said I probably have a total of $1,000-1,500 into setting it up, in terms of parts. Jets, air bleeds, emulsion bleeds, metering blocks. It all adds up. In the end the carb will run with what it needs, and the rest of the parts used for tuning sit neatly in a box, ready to be used again(possibly) when something gets changed down the road. In terms of the total into the carb itself as it will sit on the car with what it needs to run, somewhere in the region of $700-800.

It's basically an annular booster mechanical 650, with a pair of these http://www.quickfueltechnology.com/m...-cir-5eml.html And I have a large collection of these http://www.quickfueltechnology.com/m...-bleeds-1.html As well as 3 different air bleed assortment kits, a mountain of jets, gaskets etc.