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Has anybody switched out their quadajet for a EFI Carb on a 400 CI ?? If so how difficult was it? What brand did you use and how did it change the performance? Thanks in advance.
 

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Has anybody switched out their quadajet for a EFI Carb on a 400 CI ?? If so how difficult was it? What brand did you use and how did it change the performance? Thanks in advance.
Here is some reading for you. Click on the links and it should answer your question.




 

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Cameo Ivory 1967
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Many people have and there are many threads on it here. My 2 pieces of advice would be:
  1. Not to be fooled by the entry level pricing of some... by the time youre done, you will spend $2000.
  2. Yes you will get better mileage, response, and ease of operation, but you wont get more maximum performance unless your current carb is not tuned well... However, most carbs are not jetted on a dyno, so yes you'll likely "feel" more power, IMO
 

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Discussion Starter · #4 ·
Here is some reading for you. Click on the links and it should answer your question.




Thanks for all the info.
 

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1967 400ci/TH400
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I installed a SNIPER EFI on my '67 GTO 400ci - my 2 cents; easy to install but won't fit as is on stock GM manifold spreadbore. You'll need a thick gasket riser or a square bore manifold. You'll also need to install an electric fuel pump, new gas lines / including a return; Sniper has built-in regulator for 59psi. Found it easier to order Holley fuel tank with electric fuel pump which was a direct fit. So when all done, like @armyadarkness said, you'll be hitting $2000+. Runs very well, very responsive throttle BUT....I've gone back and installed a Quickfuel carburetor. Had an issue with my distributor cap which took a while to diagnose....small crack in one of the terminals and rotor was rusted. SNIPER EFI sensor kept thinking A/F ratio was too low so kept dumping fuel in carb, leaking out of exhaust manifold and puddling out of exhaust. Called HOLLEY and they told me to reset / reload firmware and software which I did. By then spark plugs were fouled so changed those. The A/F sensor still was off, I suspect the 02 sensor in exhaust also got fouled.as well...so kept dumping fuel. Got frustrated and put a Quickfuel carb....runs great and easy to tune. So I'm torn - I have one on my '68 C3 and runs great. If things go sideways, much harder to fix issue with a SNIPER on board.
 

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Seeking information on a 1969 Judge my folks owned
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I also have to wonder about replacement parts when sensors, injectors, etc. start going awry. Hidden costs like that can also be a major factor. Lots of low-budget folks like to buy nice cars like BMWs and Mercedes, then have to park it when they realize they can't afford to insure, repair or maintain it. Just my $0.02.
 
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My modern cars have fuel injection, 60 PSI, sensors and computers. They run great, but on my ‘66 I prefer my Quick Fuel Carb, can tune in every circuit, idle, power valve, power valve channel restrictions, main and secondary jets, accelerator pump etc and curve all for the proper AFR…..so it runs very good, but I want it different than modern cars.

Many guys like the FI and there are many advantages. So really a preference.
 

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Must have missed this thread. For anyone interested in FI on a 400, i put a Holley Sniper on a pontiac 400 in a ‘77 trans am. Ran great with no issues for 2 years. He had edelbrocks version of the RA4 cam, edelbrock performer heads and an edelbrock performer intake. We used a spacer to fit the spread bore. Did an inline fuel pump with pre/post filter from the holley sniper master kit. Went with non-timing control on this setup and still ran great. We have just swapped him over to Multi port fuel injection with the Holley Terminator X for his new 461 Butler stoker.
 

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Been doing a lot of reading as I am waiting for my Sniper kit from Butler. My concern is the “boiling fuel” scenario. It seems GTO44 recommends the Holley rear mount regulator/filter to solve the problem. The Butler kit comes with an adjustable Edelbrock regulator. Since GTO44 says the heat in the fuel is picked up from the Sniper/manifold, I was thinking of running the return from the regulator mounted in the engine bay. I wouldn’t have to crawl under the car for adjustments.

Although the recommended Holley regulator/filter is preset for proper pressure Im wondering how much pressure drop can be introduced, due to friction, in the line to the Sniper. If the pressure at the regulator is 59.5, what’s the pressure at the sniper. It would have to be lower due to friction loss of the tubing.

Is the Holley regulator adjustable? If so it should be able to be adjusted higher to achieve the proper pressure at the Sniper.

Maybe I’m overthinking it but I would appreciate opinions.
 

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Been doing a lot of reading as I am waiting for my Sniper kit from Butler. My concern is the “boiling fuel” scenario. It seems GTO44 recommends the Holley rear mount regulator/filter to solve the problem. The Butler kit comes with an adjustable Edelbrock regulator. Since GTO44 says the heat in the fuel is picked up from the Sniper/manifold, I was thinking of running the return from the regulator mounted in the engine bay. I wouldn’t have to crawl under the car for adjustments.

Although the recommended Holley regulator/filter is preset for proper pressure Im wondering how much pressure drop can be introduced, due to friction, in the line to the Sniper. If the pressure at the regulator is 59.5, what’s the pressure at the sniper. It would have to be lower due to friction loss of the tubing.

Is the Holley regulator adjustable? If so it should be able to be adjusted higher to achieve the proper pressure at the Sniper.

Maybe I’m overthinking it but I would appreciate opinions.
We’ve got a bout a dozen restomods running around with the rear mount regulator setup with no issues. I tested the fuel pressure at the inlet of the sniper the first time we used it and it was right at 59-60psi. There’s nothing wrong with doing an adjustable reg in the engine bay. You just end up spending more money on the extra fuel line for the return. Plus the holley rear mount reg has a post filter built in. Less fittings and 1 less component to mount seperatly under the car. Now if your car is boosted or making 600hp you might experience a drop in fuel pressure with the rear mount. Most cars we sniper are in the 350-450hp range. Once we get over 600hp we go to multiport fuel injection with the Terminator X.

If you live in a climate thats not very hot and you have a phenolic spacer you can just use the built in reg and see if you run into the hot fuel issue. 1 customer drove his car for about 8 months before he had the hot fuel issue pop up. We live in florida where its always 95 to 100degrees and 1,000,000,000% humidity. It may not be as bad for you.
 

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Aren't these system nothing more than a TBI? I have a 1990 jeep YJ that was TBI and the ecu crapped out (impossible to get the 2.5 ecu). I took the TBI off, pulled the dist and ecu. Made an adapter plate for a webber 32/36, installed a vacuum advance dist from an 85 2.5l cj, duraspark ignition and accel coil. It now gets 17MPG (up from 12) and will roll 75mph on 32's in 5th. The general consensus is if you're running 31's or bigger on a 2.5l, you might as well forget you even have 5th gear so going 75 in 5th on 32's is practically unheard of... So TBI has kind of left a bad taste in my mouth so to speak and I'm leery of trying it with my 69...
 

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Aren't these system nothing more than a TBI? I have a 1990 jeep YJ that was TBI and the ecu crapped out (impossible to get the 2.5 ecu). I took the TBI off, pulled the dist and ecu. Made an adapter plate for a webber 32/36, installed a vacuum advance dist from an 85 2.5l cj, duraspark ignition and accel coil. It now gets 17MPG (up from 12) and will roll 75mph on 32's in 5th. The general consensus is if you're running 31's or bigger on a 2.5l, you might as well forget you even have 5th gear so going 75 in 5th on 32's is practically unheard of... So TBI has kind of left a bad taste in my mouth so to speak and I'm leery of trying it with my 69...
And understandably so, as the lion's share of TBI systems, if not all, were speed-density controlled, and very cut-and-dried, meant to supply fuel and that's it. Not much in the way of tunability. This is why mass-airflow systems became all the rage, as they offered a great deal of flexibility and ability in adapting to modifications, much like a carburetor. Though in your situation, I can understand the lack of parts availability -- If a mass-air multipoint or throttle-body-injection setup could have been adapted to your 2.5, I believe you might have a different opinion. Speed density is indeed the dregs of electronic control.

EDIT: I'll add, OP, that an aftermarket batch-fire mass-air system would likely perform much better than you might expect, however, be aware that any component failure would put you in the same boat as with your 2.5L Jeep, as auto parts stores generally don't stock replacement components for these systems, which would have to be shipped.
 
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Been doing a lot of reading as I am waiting for my Sniper kit from Butler. My concern is the “boiling fuel” scenario. It seems GTO44 recommends the Holley rear mount regulator/filter to solve the problem. The Butler kit comes with an adjustable Edelbrock regulator. Since GTO44 says the heat in the fuel is picked up from the Sniper/manifold, I was thinking of running the return from the regulator mounted in the engine bay. I wouldn’t have to crawl under the car for adjustments.

Although the recommended Holley regulator/filter is preset for proper pressure Im wondering how much pressure drop can be introduced, due to friction, in the line to the Sniper. If the pressure at the regulator is 59.5, what’s the pressure at the sniper. It would have to be lower due to friction loss of the tubing.

Is the Holley regulator adjustable? If so it should be able to be adjusted higher to achieve the proper pressure at the Sniper.

Maybe I’m overthinking it but I would appreciate opinions.
 
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