To EFI or Not EFI, that, and which one, is the question.

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Animal Lawyer

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So, I swapped the engine, stock '73 oc 351c to '71 cc 351c with mild cam and oil mods w/ blue thunder manifold (+ ~100hp) Hookers (the less expensive painted long tube model) and upgraded from a toploader to (eventually, after a host of problems with the 1st T5) a T5 z-spec. kept the Holley-rebuilt SA670 carb.

No matter how much adjustring, the carb kept popping on acceleration and puffing black soot (only see that when the car is starting to move, I assume it does it at speed but cant see the fine black powder then. I'm told it's from dumping too much fuel) and the electric choke never seemed to work correctly (or the mechanic, who I tend to trust really couldn't get the carb dialed in correctly) Finally, on Wednesday, the car lost power on the parkway, necessitating a tow (thank heaven for Haggerty Driver's club). Turns out choke was jammed shut and the fast idle cam was damaged. He also says the idle adjustment is not working 100% and he thinks there may be internal damage from the small backfires., but it is running well now. 

Started thinking about switching to efi (though part of the reason I decided to switch to a muscle car full-time was because I was sick of asking my bmw's ecu "mother may I?" every time I did anything. (Went from 50+ fuses and relays to 7 fuses and 3 relays, and a whole different set of headaches). So, I'm not sure I want to go back to computer controlled engine/fuel, but I am doing my due diligence.

I have read about various issues with the swap, including needing new fuel pump, tank, lines, header issues and needing to swap distributor (I have duraspark now) bringing the cost and frustration factor up there. I am interested in suggestions about whether to swap and if so which manufacturer and model, or if not, whether to stay with the Street Avenger 670 or go to a different carb (I have read a lot of negative comments about the SA carbs0.

Alternatively, if anyone knows a real good carb guy on Long Island, I would welcome the recommendation, and hopefully can get it all sorted out. 

Thanks in advance, luckily I always have my horse Chevy to relieve the stress (Mine's the paint on the right)

boyz.jpg

 

Bill73Ragtop

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Sounds like a considerable portion of your issues involve a carb that has multiple issues and may need to be replaced.  Compared to installing EFI (I've done it since 2005 and continue to show/drive a 69 vert with Holley EFI), replacing the carb and getting a proper dial-in is considerably less expensive.

As much as I enjoy EFI on a vintage mustang - it's trick, it's better all-round performance, better efficiency, etc - there have been many, many times when I was preparing to ditch it all and go back to a carb.  When something goes wrong with EFI, its a whole lot more time, effort and $$ to find the cause of the issue and resolving it.  I'm not up to date on the current  quality carb selections available these days - there are plenty of forum members who can offer good suggestions - so hopefully they can chime in.  

I would estimate your ballpark base budget for all new component EFI conversion is probably in the $3K range (EFI system, ignition system, fuel tank & pump, fuel lines, etc PLUS someone to properly tune the EFI).  Not figured is labor if you have someone who knows what they are doing to install it properly. Hope this helps a little.

 
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I really like my FiTech EFI. They are not completely bolt on but they can work "well" very quickly. There are many ways to go about it, but if you go with a FiTech or Holley TBI unit, use a sump pump style like the Robbmc, get the new hoses around the engine bay,  add wiring and fuses, I think you can get it done for about $1,500. Maybe a bit more if you go with timing control since you will have to change the distributor. Actually, w/o timing control, it may be cheaper since FiTech has a cheaper unit if not timing control is desired. You can follow my build thread and posts about my setup. The sump pump uses the mechanical pump so you don't have to mess with the tank or existing fuel lines. I used the charcoal canister vent line as a return. The sump pump doesn't need a "full" return line like and inline pump.

Robbmc pump: http://robbmcperformance.com/products/powersurge.html

 

Fabrice

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I'm gonna get lynched in public for saying this: carbs are obsolete!!!
Too much plusses with EFI to even look back really.

Even with the few troubles I got along my learning way (all my fault), to me this is the best investment I ever made and already have another Sniper ready for my 429.

 
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Sheriff41

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Tuning a carburetor is an art.  Unfortunately, there are not too many artists left!  Fuel injection takes all the guesswork out of it and will be better in most applications, IMHO.  Someday, when I can justify it, I'll make the switch to EFI.

 

TheDude

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I think this is this one of those things that can be as simple or complicated as you want to make it and range from pretty affordable to very expensive. If the goal is to just replace a carb with something that's easier to live with, you can do that without breaking the bank IMO. But most people tend to do a lot more than just want to swap out for something more usable and look at upgrading to do a lot more. 

Like @tony-muscle above, I'm using a FiTech EFI. Don't have anything to compare to, but it's been almost all good stuff for me. From the very first turn of the key, it's run better than my old the carb had for me. I'm using the basic version with no timing control so no distributor needed. Using an external pump and plumbed the return into the sending unit cover, so no new tank. Using the factory line as the return and a high pressure EFI rubber line for the supply with no sump tank and so far that's been working great for me.  

All in I'm well under $1K and things are great. Of course I don't have all the bells and whistles of some of the EFI models, but I don't think I need or even miss any of them. Maybe if I was racing the car or something like that those features would be more important. I love that there are no cold start issues and that I can tinker as much or as little as I want to get it working how I want and usually without getting out of the drivers seat. 

 

Kilgon

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I just switched over from a Holley 850dp to a Sniper. I had mix emotions on switching over to a efi.  Taking one of these cars and putting modern technology under the hood sort of seems wrong. 

Although I haven't driven the car yet I'm am impress with the overall performance of it just running the engine in the garage.  The engine starts a lot easier and idles better.  I have also notice that the a/f mixture holds more steady. I already have a AEM O2 on it.  I put the Holley's O2 about 8" in front of it.  The both read almost dead on with each other but the AEM fluctuates more.

I have a new Hyperspark dizzy order and am anxious to get it.  I have already built a timing curve table for it.  I can't wait to get everything together and to get it out on the road.

@tony-muscle suggestion with the robbmc would be the the simplest way to go but not necessarily the cheapest.   I do like the idea that with the robbmc very little has to be changed or added.  

I got a feeling that I'm going to end up like @Fabrice and will never want anything to do with a carb again.

 
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midlife

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I'm gonna get lynched in public for saying this: carbs are obsolete!!!
Too much plusses with EFI to even look back really.

Even with the few troubles I got along my learning way (all my fault), to me this is the best investment I ever made and already have another Sniper ready for my 429.
Get the stake with kindling at the base ready!  Burn the witch!

 
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73 Grande will undergo three phase build process. Phase 1 is to make roadworthy. Phase 2 is interior/exterior restoration. Phase 3 is ++ performance.
Ok, my 2 cents, for what it’s worth (<2c); I think the answer depends more on you than on us. Why do you have your car? What does it do for you? I believe there are two main types of “vintage” car owners, makers and keepers. The makers look forward to the challenges in figuring out the issues and struggles of keeping their car on the road, or taking it from something left for dead, and bringing it back to life. For the most part, keepers just like to wash and wax their cars.

If you’re a maker, you ought to resolve the issue why you’re having troubles with the carb; it’s a bit giving up to go to the EFI (I’m in the middle of doing EFI, but I’ve got my story straight on why 😀). If you are really more of a keeper, buy a complete EFI kit and do the retrofit; you’ll spend less time under the hood, and more time waxing the hood 🤔. Just my, now, 1 1/2 cents worth.

Note: I have friends who are both, so one isn’t better than another; it’s just important that you know who you are, or you can get very frustrated. Signed, Dr. Phil.

 

detritusmaximus

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Sounds like the problem is either carb or something else. Pretty obvious saying that, huh? If its the carb, then a different carb should fix it. If its not the carb, the the problem may still be there with EFI. I would try another carb first, just to see, even if you decide to EFI. Theoretically, a different carb would fix it or have different problems. If it's the same problem, look elsewhere. EFI is an expensive way to go find out the carb wasn't it.

A question for you guys running EFI...are there fuel/pump shutoffs in your systems? Do they control fuel pump operation or is your pump on a separate circuit that doesn't shut off if the EFI shuts down?  This is a consideration in accidents. The motor stops, key is still on, and the pump keeps spitting fuel out of a damaged line.

 
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73 Grande will undergo three phase build process. Phase 1 is to make roadworthy. Phase 2 is interior/exterior restoration. Phase 3 is ++ performance.
Most have an inertia switch that triggers in an accident, turning the power to the pump off. When you retrofit a system, you should never remove this and if it doesn’t have one, they’re easy to add.

 
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Most have an inertia switch that triggers in an accident, turning the power to the pump off. When you retrofit a system, you should never remove this and if it doesn’t have one, they’re easy to add.
+1 on the inertia switch. I added one through a relay to the EFI.

Another advantage with the Robbmc pump setup is since you keep your mechanical pump, if the EFI stops working, you can have the old carb as a spare working in little time.

 
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Bill73Ragtop

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A question for you guys running EFI...are there fuel/pump shutoffs in your systems? Do they control fuel pump operation or is your pump on a separate circuit that doesn't shut off if the EFI shuts down?  This is a consideration in accidents. The motor stops, key is still on, and the pump keeps spitting fuel out of a damaged line.
Mine is installed in the trunk mounted on filler tube support braces.  It's wired into the power supply side wiring for the fuel pump.  Fuel pump operation is controlled by EFI ECU.  Pump is turned off by EFI if engine is not started within 15 seconds of turning key to power.

 

Omie01

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Sounds like most people are open to the EFI. I don't hate the idea, but I feel it takes the retro spirit out of the car. I hated carbs until I bought a custom built unit from Pro Systems. I filled out a whole spec sheet on my engine build and they shipped me a custom DP Holley. In 5 years it has not changed in how well it runs. I did the initial tune, (which was really easy) and have had no need to look back. And one time for kicks I swapped to a regular Holley 750 DP (for the choke) and instantly lost around 40 hp. It was VERY noticeable. This year I have to install a few new gaskets as I do have a small leak at one of the bowl screws but that is the only problem in 5 years. Needless to say, maybe just a custom carb from a reputable builder is the way to go. My carb was $680 5 years ago, but my father just bought basically the same carb from them because he was having issues with big box carbs too, and I think he paid $100 more, so $780. And they always take the time to assist in tuning over the phone if you need. My 2 cents!! Good luck and happy building!!

 

Hemikiller

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Popping on acceleration is a lean backfire, typically caused by inadequate accelerator pump shot or duration. If the choke isn't functioning properly, then that needs to be addressed before anything else can be diagnosed. Sometimes a "mechanic" is not the guy you bring a car that needs to be tuned. 

There's a great carb shop on LI, Allstate Carburetor. Talk to them and see if they can help, or can recommend a shop to get you sorted. 

https://allcarbs.com/

 

Fabrice

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A question for you guys running EFI...are there fuel/pump shutoffs in your systems?
That's one of the details you never hear about. I recall at the time I installed mine in 2017, that there was not even a mention about this in the install doc.
While they are affordable ( got one from evilbay as Derek VGG would say) and really easy pizzy to install. In fact they should be part of the harnesses of the EFI's that are sold or at least have a connection ready and documented for that. I mean when you pay around $1k for a unit, it's not like the added 10 or 20 that would make a diff.
I'd bet 8 out of 10 installs don't have one.

 

Fabrice

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I feel it takes the retro spirit out of the car
yeah and then comes the winter and you don't care anymore! :O Kuz after after weeks without running, you turn the key, it's 2c outside and the car starts right away with a perfect idle. At $10+ a gallon of juice here, which is hard on the spirit, I also enjoy not be as often as before at the station.
I won't say it takes the retro spirit out of the car, in my experience it awakens it! My car never been so responsive at any rpm and only discovered after the install how well it performed. Considering the diff, it's obvious I sucked big time at carb tuning, I would never have known before.

 
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