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EFI to Carb

Old 04-25-2017, 10:14 AM
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Question EFI to Carb

I'm taking out my 300 6 cylinder motor and dropping in a 351m. The 300 is electronic fuel injection and the 351m has a carbureator. What all do I need for my truck itself to change it over so that the carb motor will work?
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Old 05-18-2017, 09:24 AM
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You will need a fuel pressure regulator they have special ones for EFI to carb swaps with built in bypass and the associated hoses and fittings. Or you will have to pull your fuel pumps and get an exterior fuel pump. New distributor either a hei distributor or duraspark setup. You have to wire your fuel pump to a 12v ignition wire. That should be it as long as you have a manual trans or an older automatic. I swapped my 302 from EFI to carb last year....I think with the 351 you will have to get another radiator, hoses, and motor mounts.
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Old 05-20-2017, 10:27 PM
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A couple of comments on this:

1) If it is a 351M you will need to change the transmission because they will not bolt up. 351M use the big block bolt pattern for a 429/460 while your 300 uses the small block bolt pattern.

2) unless the 351M has been rebuilt recently I would check the bearings. Those engines are notorious for wide bearings and having no oil pressure because of it. After 150k on my rebuilt 400 I ran into that problem myself.

3) You really would better off getting a 351W due to the transmission issue, even if used it will probably have a longer service life.

4) Other than the engine itself, you would have to get all of the non-EFI components as with any engine swap - it's been done a bunch before so you probably can google someone else's work on it.

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Old 06-15-2017, 08:03 PM
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best bet is to dump the EFI fuel pump and go with a carb pressure fuel pump. i tried using a pressure regulator, two of them in fact, when i swapped a carb for EFI on my old 83 grand marquis, and the pump just blew the fuel past the regulators and flooded the carb as if the regulators were not there.
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