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Old January 3rd, 2012, 11:29 PM   #1
drogers
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Default what carb to use on a 4.3

i got a 4.3 on a deal. it has be bored .60 over looks like it has had head work . it might be stroked ( have to look at it more ). what size carb do u thing i should run .
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Old January 4th, 2012, 06:21 AM   #2
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Need more info on the build - i.e. cam/intake/exhaust and how you want to drive it, but just running the CFM calculations on a 4.5L engine @ 85% VE, it would need a max of 370 cfm.

Seems like a Holley 390 CFM 4 barrel or 350 CFM 2 barrel would work well. If you're going to run it is an offroad rig, TBI would be your best bet, and I can help you out there.
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Old January 4th, 2012, 08:17 AM   #3
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TBI for sure.
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Old January 4th, 2012, 08:35 AM   #4
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a stroked 4.3L crank is $$$ big money.
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Old January 4th, 2012, 09:56 AM   #5
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TBI x3. Just did it, it was cake. But if you need a carb I have a Holley 350 two barrel just professionally rebuilt I will sell you. $150.00
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Old January 4th, 2012, 10:15 AM   #6
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It depends on what you are doing with it.TBI for sure if you are going off road a lot,as long as your cam isn't to radical.If it has head work,more compression,and a bigger cam you could probobly use a holley 600 vacume secondery.I personally dont think the 390 cfm is enough,and I never believe cfm calculaters for carbs.Every motor I build happily uses more carb then the calculater claims it needs.
The 4.3 used in boats made about 25 more hp then the ones offered in cars and trucks,they came with a none computor controlled quadrajet,that is the carb I would probobly use,and modify as needed.
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Old January 4th, 2012, 03:31 PM   #7
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If its got a performance cam I would consider an Edelbrock 600 cfm with Edelbrock# 1485 jet and rod kit for 4.3L Marine engines.
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Old January 4th, 2012, 03:59 PM   #8
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I also have a brand new Holley 500 marine carb w/electric choke tuned for a 4.3L. It was to fat for a stock 4.3L $150.00.
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Old January 5th, 2012, 05:42 AM   #9
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Quote:
Originally Posted by bdd1469 View Post
It depends on what you are doing with it.TBI for sure if you are going off road a lot,as long as your cam isn't to radical.If it has head work,more compression,and a bigger cam you could probobly use a holley 600 vacume secondery.I personally dont think the 390 cfm is enough,and I never believe cfm calculaters for carbs.Every motor I build happily uses more carb then the calculater claims it needs.
The 4.3 used in boats made about 25 more hp then the ones offered in cars and trucks,they came with a none computor controlled quadrajet,that is the carb I would probobly use,and modify as needed.
I'll agree with you on all of that, except to a point; IMHO - for best driveability, the smaller carbs can't be beat for low end and part-throttle response. That's where the CFM calculator comes in handy; you can verify the theoretical need of your engine displacement.

A quadrajet is also an awesome answer - but when I've suggested them in other places, people come back with anything but love. Small primaries for great throttle response and secondaries that open only as far as needed.
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Old January 5th, 2012, 06:34 AM   #10
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Quote:
Originally Posted by ScOoTeR View Post
I'll agree with you on all of that, except to a point; IMHO - for best driveability, the smaller carbs can't be beat for low end and part-throttle response. That's where the CFM calculator comes in handy; you can verify the theoretical need of your engine displacement.

A quadrajet is also an awesome answer - but when I've suggested them in other places, people come back with anything but love. Small primaries for great throttle response and secondaries that open only as far as needed.
About the q-jet most don't know how to tune them, or start with a worn out carb to begin with and wonder why they can't make them work. I ran with a 830cfm known as the 850cfm from an l88 that was tricked out. Boy did it have throtle response.
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Old January 5th, 2012, 07:22 AM   #11
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^ Werd.

Having experience with motorcycle carbs helps decipher a Q-jet.
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Old January 10th, 2012, 09:13 AM   #12
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all right thanks for the info
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