Help with carb swap

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May 30, 2015 | 06:00 PM

XLT GOLD 84

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Help with carb swap

Hi I'm still new to FTE and I'm wanting to swap my stock 2bbl for a 4bbl but I'm having trouble deciding which one. I have a 1984 F150 302 and it's my first truck and its carborated so I want a kinda simple 4bbl but what do recommend for a swap. I'm hoping to do a swap with. A month so I have some time to decide any help or tips is appreciated.

Jun 3, 2015 | 01:33 AM

baddad457

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From: south louisiana

Easiest thing to do is swap to a 500 cfm Holley 2 bbl, or a 350 cfm Holley 2bbl. Both will bolt right in place of the stock carb. You will need to address what to do with all the emissions crap though, no matter what you do. To do a 4 bbl, you'll need to swap the intake manifold too. Most common 4 bbl for this is an 1850 Holley 600 cfm 4 bbl. May as well do the 350 cfm Holley 2 bbl though as your motor will never use the secondarys on the 600 cfm Holley 4 bbl. The only way you'd get them to open up would be to rev it out at WOT on the open road after changing the secondary spring to the lightest one they offer. With the spring these carbs come with, the they'll never open up at any rpm less than 5 grand. And by that rpm, your motor's done making any kind of power.

Jun 8, 2015 | 12:48 AM

FordFETruck

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From: Algona,WA

http://www.summitracing.com/parts/su...2LsaAn6i8P8HAQ

Annular boosters,(REALLY helps with fuel atomizing) externally adjustable floats, top of the carb comes off. Makes for 10 minute jet changes. Modeled after the Autolite 4100. Uses all common Holley tuning parts. Vacuum secondaries are load sensitive, they open when the engine vacuum reaches a certain point under load, and are triggered by many different factors. Not just "5000 RPM because it's a tiny 302". And is adjustable with about 7-8 different springs you can put in there. A 302 will be in to the secondaries plenty. What about those factory 4bbl 289's Ford produced?

Besides that, most 2bbl's don't have as crisp of throttle response as a 4bbl. They're also ugly IMO.

As far as an Intake manifold. Either an Edelbrock performer or a performer RPM. Which ever you feel like getting. Just don't get a single plane intake.

Jun 8, 2015 | 08:35 AM

baddad457

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From: south louisiana

Quote:

Originally Posted by FordFETruck

Vacuum secondaries are load sensitive, they open when the engine vacuum reaches a certain point under load, and are triggered by many different factors. Not just "5000 RPM because it's a tiny 302". And is adjustable with about 7-8 different springs you can put in there. A 302 will be in to the secondaries plenty. What about those factory 4bbl 289's Ford produced?

Besides that, most 2bbl's don't have as crisp of throttle response as a 4bbl..

You obviously didn't read what I posted. With the secondary spring Holley puts in a 600, the secondarys will never open on his 302, no matter what you do or how you drive it. And only after changing that spring to the lightest one, will they open then. But if the motor will actually put the extra fuel to good use ? That's open for debate, his motor is all done making power by then. As for the 2 bbl not being as responsive as a 4bbl, the 350 cfm 2 bbl has smaller throttle bores and venturis than the 1850 600 4 bbl. So that part just ain't true. The old 289 was more motor than the 302 the OP has now, so yea it would use more carb.