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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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1967 400/400
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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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