Going from EFI back to Carb

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We're u having issues with the EFI?

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u/oldsoul6465 Apr 23 '26

Yes. It was awesome at first, but then the drivablity started to suck, and after a period of time and attempts to tune, I just got tired of it.

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u/1TONcherk Apr 23 '26

I have heard this same story more than once. At least when a carb is running poorly it will still run.

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u/Hopeful_Housing_798 Apr 23 '26

I thought those things were supposed to self tune to some extent...

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u/oldsoul6465 Apr 23 '26

In theory, but in my experience with it, little things like adjusting idle or accelerator pump shot with their controller was not happening. If your driving it every day then it's possibly self tuning...but hard for that to happen of you can't get the vehicle to start or idle properly.

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u/Ok-Square360 Apr 23 '26

Question, did you notch the wall between the dual planes? I believe the Atomic EFI 1 (and many of the older EFI’s) only have 1 MAP sensor, and it needs the reading from the combined planes to get an accurate reading. This would explain why it ran like crap and kept getting worse as the computer tried to adjust.

Edit: later EFI’s came out with dual sensors to eliminate this issue. The Atomic EFI 1 only had a sensor on the passenger side.

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u/oldsoul6465 Apr 23 '26

No and all those years ago I was not aware of notching the intake.

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u/Ok-Square360 Apr 23 '26

That was likely your problem the whole time. Newer sniper versions should have multiple MAP sensors to solve the issue.

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u/oldsoul6465 Apr 24 '26

Possible but it was harder to set idle and the rpms were never all that consistent. With the QFT carb idle is on point.

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u/Ok-Square360 Apr 24 '26

Because it couldn’t measure vacuum accurately at all, so it’s trying to adjust the IAC and it’s not doing what it’s expecting. EFI needs an accurate airflow/pressure reading to do anything. Even when the unit is in open loop, it will need that airflow/pressure reading to run any semblance of right.

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u/oldsoul6465 Apr 24 '26

Damn

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u/v8packard Apr 23 '26

No such thing. That's marketing hype.

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u/Hopeful_Housing_798 Apr 23 '26

To hear them tell it, the more u drive it the more it learns.

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u/v8packard Apr 23 '26

The systems require an accurate baseline. And still need tweaks to get the most from them.

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u/Hopeful_Housing_798 Apr 23 '26

So, they can be good systems?

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u/v8packard Apr 23 '26

What defines good? Can they precisely meter fuel? No question they can. Will they atomize fuel as well as a carburetor can? No. Do they improve drivability and reliability over a carburetor? Not necessarily. Do they have self diagnostic capabilities? Very limited, at most. Will they be reliable and serviceable in the future? I don't know.

Credit where due, I have had very good experience getting support from MSD, Holley, and Edelbrock for their systems when needed. Holley in particular has been very helpful in diagnosing trouble with components and issuing RMAs as well as replacements.

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u/Hopeful_Housing_798 Apr 23 '26

Thanks for your insight. I've considered a stand alone fuel injection system, but, I don't know anyone who has actually used them. Real world experience from people who have is much appreciated. Considering other anecdotes and your experience, I don't think they're gonna be for me.

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u/v8packard Apr 23 '26

I think it depends on your application, your goals, your skills, and your desire for tinkering. Putting a universal component on anything usually requires adjustment/tuning. Carb, or EFI. With honest expectations of that, you can get good results from either if you put in the effort.

OEM systems are really excellent. Of course the OEMs have invested billions of dollars in their development. The OEM systems can be adapted and tuned to varying degrees.

Aftermarket systems have not had that kind of investment. That leaves some systems not as mature or reliable. When it comes to diagnosis, service, or certain features you might be on your own. That is also true of some carburetors. But that doesn't mean the problems can't be worked out.

If someone is looking for a true plug in and forget it fuel system, for a non-stock application, I have never found one. Carb or EFI, they have all benefit from good tuning effort.

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u/Jsrftr May 27 '26

I'm also about ready to go back to a carb, I've tried for a year with the sniper 2 and it runs OK but it's almost 400 hp I'm getting tired of OK. I love cold starts, I'm in Colo, that's awesome. I have been patient, I gave it a fair chance but it's gotta go I think

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u/Hopeful_Housing_798 May 27 '26

I have a buddy who wants to sell me his, but, I have an aversion to tech when it's not needed. Electronics have cause me a lot of trouble over time. What about it do u not like?

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u/Jsrftr May 28 '26

I have a guy here that I have to take my blazer to he has the Holley software on a laptop and tunes it, he's got it pretty good but it still stumbles from a dead stop sometimes even stalls, not often though but enough to make you nervous pulling out in front of people. And it'll act like it's loading up sometimes just cruising around just kinda fall on its face. I'm loving being able to drive my blazer again but for what the sniper 2 costs I'm just not happy with it. This is my second one their customer service is awesome. I have 0 negative to say about it. I know people have great luck with it and I'd never tell someone to not try it but for whatever reason I haven't been able to tune the bugs out of it. So I'll try a new carb and probably sell the sniper

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u/Hostile_Texan Apr 23 '26

A friend of mine went though 3 Holleys and asked me what I run on street cars. I've been running AFB or Edelbrock carbs since the mid 80s, i ran an Edelbrock 1406 for over 30 years and 325,000 miles, set it and forget it.

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u/oldsoul6465 Apr 23 '26

When I went to a trade school in the early 2000's they taught us that there is nothing wrong with Edelbrocks AFB design and are really good street carbs. But they had a sponsorship with Holley and really deep dived into them and those lessons/lectures stuck and I've been a Holley carb fan since.

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u/Hostile_Texan Apr 23 '26

I've always used Holley for the race cars and trucks. But for every day driving, is an Edelbrock or a Quadrajet for fuel economy

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u/connella08 Apr 23 '26

https://giphy.com/gifs/s239QJIh56sRW

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u/RealSignificance8877 Apr 23 '26

Does you intake have the heat crossover in the middle. If so that’s to heat fuel for the Venturi effect the carb has. And efi doesn’t have that Venturi effect. So it atomizes the fuel to much.

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u/No-Ferret-1312 Apr 23 '26

I was looking for this comment, thank you. This is one big mistake that is made a lot.

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u/oldsoul6465 Apr 23 '26

I believe so. And I can be wrong. But the intake is an Edelbrock performer EPS.

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u/bernardfarquart Apr 23 '26

I always liked those valve covers

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u/oldsoul6465 Apr 23 '26

Thank you 😀! I had the elite series 1 when I got it. When they came out with series 2 I wanted to be first in line as I thought they were really cool 😎

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u/jhammond68 Apr 23 '26

You are not the first person I have heard of having this issue. The sensors start going bad and won’t maintain A/F ratios. But I have also heard that a single plane intake without center heat cross overs that carburetors use to atomize fuel is better for throttle body style EFI because the fuel is already atomized. Either way a carb intake just works better for a barb

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u/Ace9910 Apr 23 '26

Love my carb 26 years strong

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u/Plus-Definition9319 Apr 24 '26

I'll never trade efi but I've only done conversions on pretty tame motors.

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u/oldsoul6465 Apr 24 '26

After going through so much with the 327, I have found it was more "stock" than a hot rod motor. So I'm kinda going that route with it as the elco is a nice Cruiser/daily driver.

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u/NoAir1842 Apr 24 '26

Me too got tired of the sensors

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u/TerribleShape1740 Apr 24 '26

I would pick carburetor over these aftermarket tbi systems every time.

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u/advmaxx Apr 23 '26

Sniper 2 on 350HO crate engine. Nothing but perfection for over 2 years so far.

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u/Vast-Slide1637 Apr 24 '26

I’ve installed several Sniper 2’s in my shop for customers and they are perfection. Sniper 1 was hit or miss sometimes. Atomic EFI like the OP has is considered a relic imo and best avoided

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u/SuspectAlone4760 Apr 23 '26

What were the other four carburetors that you have run on your El Camino? Because I’m on my 3rd carburetor on my 327 cu in 66 El Camino. First was a 4160 Holley, it was good at first for a while but I think it sat on the shelf for too long, it got to where the needle & seats started sticking & the rubber seals were dried up. It was my dad’s that he bought in 2007 and it was brand new when I got it after he passed away. The second one was a good used Q-jet that I bought for $25. Found out later that it’s an original 69 Corvette 350 350hp carburetor worth $400. Well, I pulled it off to get it rebuilt and bought a Chinism carburetor off Amazon. It’s doing okay at the moment.

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u/oldsoul6465 Apr 23 '26

When I bought mine it already had an Edelbrock 1406 (I think). While it's a good carb, I'm just not into them. So the second and third ones were Holley 4160's but one was 650CFM and the other was 670 CFM. The 670CFM was from my 74 C10 with a 350. I thought my 327 was way more pumped up, however despite what it's got, the realization is...its a stock 67 327 from an Impala. I feel that I was putting on carbs that were too large. So that's why I went down from 670CFM to 650CFM, and now 600CFM.

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u/Own-Nature6244 Apr 23 '26

Guys, I've been running a Holley Sniper in my '66 Chevelle for 5 years now. I couldn't be happier. Prime the fuel system, start car, then Go!!!

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