Small-block Chevy: Toss carb for fuel injection?

[Dantilla]

I've got an older Chevy pick-up powered by a 350 using an Edelbrock carb.

I'm re-thinking plans to toss the engine for a newer LS-based engine, prolly a 5.3.
The 350 runs strong, but uses gas like.... An older Chevy pick-up.

MSD, Holley, and a few others make bolt-on kits that toss the old-tech carb for a fuel injection system that sits on the existing intake manifold.
Looking around the internet, lots of opinions (duh!), but everybody who has actually installed one has nothing but good things to say

-Way more better fuel mileage
-No more "gassy" smell in the garage
-Overall increase in power
-Better throttle response
-Yada, yada

Local auto parts guy showed me the MSD kit. Besides the throttle body, sensors and controller, comes with fuel pump, fuel filter, even new fuel hose, guesstimated install time of four hours, complete.

Anybody have experience, or want to add more internet opinions?

[GH85Carrera]

Do it. Don't look back.

I took off my OEM POS carb (Rochester Computer controlled) from my El Camino 15 yeas ago. I went with just throttle body FI and it starts and runs like a modern car and get 3 to 4 MPG more than the carb did. The real bonus is when it is below freezing the car fires up instantly and just runs fine, or if it is 105 and the engine temp is 210 and I shut it off for 30 minutes it just starts instantly. Over 150,000 miles of trouble free injection and no hesitation at all. The old carb was scary in some situations pulling across a street or into traffic.

Back when I did my conversion it was mostly find the parts and make it work thing. Now there are tons of kits on the market from complex to simple.

The biggest reason I did the throttle body was it did not require a new intake manifold (or exhaust) and it was just a long weekend working by myself.

[Instrument 41]

Yes, yes and yes. You can find a kit that will bolt on to your existing intake. Unless your 350 is just tired I'd keep what you got. Not real cheap but well worth the money.

[patz]

I did an Edelbrock FI conversion on a 454, better gas mileage, HP and ran great. Do it.

[wdfifteen]

No options, just nostalgic for the the gassy smell and the moan of a four barrel at full throttle. I feel sorry for people who may never experience that.

[A930Rocket]

I have a friend that went from EFI to carb on his mustang. He worked for years on the car's EFI to get iit right, but it just didn't work right (granted it was a track car that was making stupid RWHP). The carb wasn't as efficient but it worked great.

[sammyg2]

LOL, reminds me of something I wrote a long, long time ago. Please forgive the simplicity of it:


CARBURETION OPERATION AND THEORY

FUEL DELIVERY
The fuel pump pressurizes the fuel to around 3 to 5 psi for carburetors.
The fuel flows through a filter (hopefully) and into the carburetor float bowl chamber.
As this chamber fills, a float on a pivot rises with the level. As it gets high enough, it closes a valve, shutting off the flow of fuel. When the level drops, the float valve opens again and lets in more fuel.

IDLE CIRCUIT
The engine wants to run fast all the time. The throttle plate controls the engine by restricting how much air it gets.
The engine tries to pull more air in but the carburetor won’t let it at idle. This pulling causes vacuum, an area of low pressure in the manifold.
There is a small hole in each of the throats of the carburetor just below the throttle plates.
These holes are connected to a passageway that goes up, then back down to the float bowl.
The vacuum pulls fuel from the float bowl, up through a restriction orifice (jet), and down into the manifold. Most carburetors have a needle adjusting screw that adjusts how much fuel flows into the throat. Many also have small holes in the passageway that let air in so that it mixes with the fuel and starts to atomize it so that it is well mixed as it enters the manifold. Some have idle mixture screws that adjust how much air is allowed into the passageway.

TRANSISTION CIRCUIT
As the throttle plates (butterflies) start to open, they expose a second set of small holes that are also tied into the idle jet passageway. As the butterfly passes these holes, the vacuum pulls fuel through them and mixes it with the higher velocity air that is rushing to squeeze through the small opening. Remember, there is low pressure below the throttle plates, but normal atmospheric pressure above them (except for full throttle high rpm conditions). Some carburetors have one transition port, some have as many as three or four. Their purpose is to try and correctly meter the amount of fuel so that the right ratio of fuel to air is maintained. Most driving is done in this circuit.

ACCELERATOR PUMP
When the throttle is opened rapidly, the manifold vacuum can suddenly drop to near zero. No vacuum, no fuel gets sucked into the engine, no go. Just a big bog.
The accelerator pump is a band aid for this problem.
As the throttle is opened, a piston or diaphragm is actuated, displacing fuel and pumping it right into the throat of the carburetor like a squirt gun. It mixes with the air and burns to keep the engine happy. Since the air is not moving very fast during this condition, the fuel has a tendency to puddle on the manifold floor or stick to the walls.
V-8’s use hot water or oil to heat the floor of the manifold to keep the fuel mixed up. It works, but is a major compromise.
Because the fuel doesn’t stay mixed very well during this low vacuum, low rpm condition, the carburetor has to add extra fuel so that we are sure to get enough into the motor. Not good for emissions or economy. Carburetor systems that have a single barrel for each cylinder and are mounted directly in line with the intake ports are the least susceptible to this, except for fuel injected motors. There are some problems with this type of carburetor set up (like reversion).

MAIN CIRCUIT
As the engine rpm rises, the air that is flowing through the carburetor barrel has to go through a section that is a little smaller than the rest of It (venturi). The air really wants to get through, so it has to speed up a little so that all the air can get by. So it speeds up and squeezes though the tight spot, then the opening gets bigger again. The air is still going fast and straight. Right at the tight spot there is a small area that has lower pressure than the rest of the barrel. This is caused by the air trying to keep going straight, and the velocity makes it not want to bend back to fill the entire barrel. This is called the Bernoulli principle (I hope I spelled that right). Right there where the pressure is lowest, there is a small port, or passageway that is connected to the float bowl. The fuel is pulled from the float bowl, up the passageway, mixed with a little air, squeezed through the main jet, and goes into the carburetor throat. Some carburetors have a booster venturi, but they just do the same thing the same way.

Carburetors are simple things, but try to do an impossible job. That is, add just enough fuel to maintain a perfect air/fuel mixture, no matter how much the throttle is opened, the engine rpm, the air temperature, the engine temperature, The fuel level in the throat bowl, the list goes on and on.
My father told me a long time ago that carburetor is a French word which loosely translated means “compromise”.
He may be right.
Early fuel injection systems had as much as 30 different "maps" or compensating circuits depending on input conditions, modern systems can have millions of "maps" due to the multiplication of all the variables.

Carbs work fine if you run WOT all the time, but for normal driving fuel injection rules.

[Dantilla]

Thanks for the replies! The Pelicans come through once again!

Originally Posted by wdfifteen

.... just nostalgic for the the gassy smell ...

The other thing I have to do with this truck- Right now, the exhaust dumps out the side, behind the rear wheels. This means the last two feet as I pull into the garage, all the exhaust is blowing inside. Same when I start the truck- Until I back out far enough, the garage is getting pretty stinky.

I'm going to have a muffler shop bend the tips so they dump out the rear.

Another reason- Pull up at a drive-through to get a cup of coffee, and the exhaust echoes between the building and side of the truck. Truck sounds good and all, but I'd like to enjoy the V8 lope on my terms, not be annoyed with it.

Leaning towards the MSD kit, just because it's the (very knowledgeable) parts guy's favorite.
New kid on the block is FI Tech, but their whole sales pitch is "We're cheaper than the other guys". Not interested in cheap if I do this, looking for quality. We'll see how the new guy's reputation develops.

Whatever I do, yanking the carb and bolting on a throttle body sure is easier than an entire engine/computer swap.

[BeyGon]

you can get injection that looks like you are still running carbs or Webbers, it looks good

[lin7310948]

i have mass flo efi on the all aluminum 434 sbc in my 71 911. starts right up in all temps and has excellent throttle response. and it uses ford cobra components...hence easy to find parts almost anywhere. it is also self programming after a couple of initial installation steps. i have dual wahlberg pumps installed in my fuel tank with a ford lightning fuel hat. the engine dynoes a little over 550 chp...plenty for the 2200 pounds coupe with shortbell 930 gearboxc!

[Dantilla]

Originally Posted by A930Rocket

... He worked for years on the car's EFI to get iit right, but it just didn't work right (granted it was a track car that was making stupid RWHP)...

Different kits out there- "up to 600 hp", "up to 1200 hp"

For a truck, sounds like FI is the way to go for part-throttle driving.

[Dantilla]

Originally Posted by lin7310948

... a little over 550 chp...plenty for the 2200 pounds ...

Yeah, I think we can put that in the "Adequate" category.

[RANDY P]

a complete 5.3 will yield you the most power, and the hardware is probably pretty close to the price of a NEW EFI setup. For the dollar per cost LS is the winner, however the bolt on EFI is probably easier to install- and you get a known quantity in the form of a fresh long block.

Installation will be a bit of a trick since you need to notch the crossmember for an AC compressor or invent some other sneaky way to hang the AC compressor higher for an LS setup, new A/C lines, and the rat's nest of wiring, VATS delete (security) and all that BS.

I don't know about using an aftermarket EFI on a daily driver, that thing craps out while you're out of town that would suck.

With that said, a TPI swap would get you OE quality stuff, and doesn't cost too much. Fairly simple to wire up and can be used with the current engine layout.

rjp

[RANDY P]

PSS- those TBI type setups (mimic a carb) I don't know if I would consider that- the TBI on the P/U is a dog. I own one, I know. I just leave it alone since the engine is fresh, but I had a chance to do it again it would get a 406 TPI....

[Arizona_928]

I vote for 5.3 swap. Can be done cheaper then a FI setup, if you rework your harness and use all the truck parts.

[HardDrive]

Originally Posted by lin7310948

i have mass flo efi on the all aluminum 434 sbc in my 71 911. starts right up in all temps and has excellent throttle response. and it uses ford cobra components...hence easy to find parts almost anywhere. it is also self programming after a couple of initial installation steps. i have dual wahlberg pumps installed in my fuel tank with a ford lightning fuel hat. the engine dynoes a little over 550 chp...plenty for the 2200 pounds coupe with shortbell 930 gearboxc!

Whoa. Do you have a link to more info about your car? Beast mode!

[asphaltgambler]

Really depends on your budget and expectations. I will tell you from vast experience that the Edelbrock carb is the absolute worst choice.................period for modern carburation. It is the same late 1950's 'technology' that Carter (original design / manufacturer) that was installed on late 50's / early 60's Chrysler / Dodge / Desoto products. That is not to say the rest of Edelbrock products are bad - they are, in fact, some of the best aftermarket products available. They bought the patent and manufacturing rights so they could offer a complete Edelbrock engine - IE: from air cleaner -to- oil pan for John Q Public.

Further the Holley / square-bore based designs have progressed so far that you can really buy almost the exact carb for your application with little tuning after, good throttle response and decent mileage. Advancements for street driven vehicles are down-leg (main fuel) boosters, parts not cast but precisely machined, 2- stage power valves, .5 incremental jetting choices.

Also the original GM Quadrajet is a really fantastic carb having very small primary bores and venturis with sophisticated, multi-stage transitional idle-to-main circuit for great throttle response and good fuel economy. It has huge secondary throttle plates coupled with tune-able air flow valve for performance and smooth wide open throttle

Finally, obviously, your engine must be in good mechanical shape. One low buck trick is to install a modern profile mileage / towing camshaft and lifters. The problem with older 70's and 80's SBC's are that GM reduced the profile and retarded camshaft timing in order to meet emissions. This did nothing but take away performance and return terrible gas mileage numbers. To be clear, I'm not talking about a lumpy hot-rod camshaft - Edelbrock and Crane offer just such bolt-in cam, lifter and timing gear / chain packages that with work your stock valve springs.

As your engine accrues mileage and age - the stock timing gear and chain wears significantly further retarding the cam and ignition timing resulting in even poorer fuel mileage and performance.

If you budgeted $800-$900. that would buy a complete camshaft / lifter / chair-gear package, gaskets, and a down-leg booster Holley style 650-750 carb, fresh plugs and oil change

If your budget is closer to $2000, several companies offer very good high pressure port injected set-ups that bolt-on fairly easily, are for the most part self tuning and low maintenance. One thing is for certain, whatever path you choose anything is better than the carb you have.

[VincentVega]

Great info gambler

I think FI is great but I'm not sure you'll see

Way more better fuel mileage

. Sure, a few mpg but a 350 truck is never going to get over 20mpg unless you are hypermiling/lucky/engine off down hill. The ~$900 package above is a good way to get some power and decent mpg, if you can keep your foot out of it.

[Dantilla]

More good comments. Greatly appreciated.

To do a 5.3 swap, I would do the same as with the hot-rodded 911- Buy a wrecked truck from the insurance auction.
This way, it is guaranteed that the engine, wiring harness, brains and all sensors play nicely together, as they all left the factory together.

+ Most power
+ Best efficiency
- Much longer install time
- Takes massive garage space to have both trucks in pieces
- the hassle of parting out the remainder of the donor truck
(Quite a bit of the donor 911 was disbursed at John Walker's swap meet)

The current 350 is strong. Crate engine with an "RV" cam. That's all the info I have from the prior owner. To install FI on existing engine:

+ Quick install

The other issue, the transmission. The truck has a 4-speed, and I'm keeping it a manual tranny truck. As far as I can tell, GM never sold any 5.3 powered vehicles with a manual tranny, so there is quite a bit of head scratching and custom parts building to mate the Vortec engine and clutch/tranny. I've already got an NV4500 tranny to convert from 4-speed to 5-speed. First four gears are the same, but with a 5th gear overdrive.

Other guys have mated a 5.3 to an NV4500, so it's not re-inventing anything, but it is time consuming, with lots of different parts from different vehicles to scrounge up. Only makes sense to do it all at once.

I'm leaning towards tossing the carb, installing Fuel Injection, and having the truck back on the road with the 4-speed still in place.

[asphaltgambler]

Then it is just a matter of budget. Please toss aside any TBI / throttle-body types of FI. They are nothing more than low pressure fuel / drips just like a carb. They (factory manufactures) were introduced when the need to transition from computer controlled carbs to fuel injection made sense. Compromise at it's finest.

High pressure port injection systems where there is a runner style manifold will return the best low-mid-range torque and response for your application. You should shy away from EFI systems where they utilize an intake manifold that resembles a high performance 4bbl intake and 4bbl throttle body. Those are great - but tuned for lighter and higher revving performance oriented engines. While they will work - you will be disappointed.