Offenhauser Intake Question
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Elder User
Joined: Sep 2005
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From: Brumley, MO
Offenhauser Intake Question
Ok guys I'm getting ready to do the 4 bbl intake, and EFI manifold swap. I'm kind of having a dilema. Should I buy a new intake or get a used one(I don't have paypal or an ebay account)? I will be getting used EFI manifolds. Should I buy a new carb or get a used one? I can probably find a good used carb, I would kind of like to use a Q-Jet, but I would also like a manual choke, and I don't know if thats possible with a Q-Jet. If it wasn't a Q-jet I would want a Holley Truck Avenger 470 CFM or whatever it is. What do you guys think I should do. Oh btw how much extra power do you think I will have?
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Joined: Dec 2007
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From: Boise, Idaho
Just did this swap on mine (have pics and write up if you want them). I got all the EFI manifolds, dual port Offenhauser, and Holley 390 used. The only stipulation is to be sure there are no broken mounting tabs on the intake.
If you get a used carb, and are unsure of it, just get a rebuild kit and rebuild the whole thing. You're more than likely going to be tuning, tuning, tuning anyway to get a non-stock carb to run perfectly on your engine, so buying one with factory settings isn't necessarily going to buy you a lot.
Besides: New Offenhauser: $350
New carb: $400
$750
Used Offy: $150 - $200
Used carb: $50 - $200
Rebuild kit: $30
$250 - $450
Either way, you could almost use the money you saved to take it down to a professional and have them custom tune the 4bbl to run with your engine.
As for power: You'd be roughly sitting around 160 - 170hp/ 280 - 300tq. Ballpark figure.
If you get a used carb, and are unsure of it, just get a rebuild kit and rebuild the whole thing. You're more than likely going to be tuning, tuning, tuning anyway to get a non-stock carb to run perfectly on your engine, so buying one with factory settings isn't necessarily going to buy you a lot.
Besides: New Offenhauser: $350
New carb: $400
$750
Used Offy: $150 - $200
Used carb: $50 - $200
Rebuild kit: $30
$250 - $450
Either way, you could almost use the money you saved to take it down to a professional and have them custom tune the 4bbl to run with your engine.
As for power: You'd be roughly sitting around 160 - 170hp/ 280 - 300tq. Ballpark figure.
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Elder User
Joined: Sep 2005
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From: Brumley, MO
I'm actually having my mechanic do the job. If I did it I would scew it up. He said the labor would be around 250-300 bucks. I found the intake for like $260 at Summit and Jegs. I really don't want to sign up for ebay or paypal. I know I can find EFI manifolds used locally, but I won't find a 4bbl intake for a 300 six.
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Joined: Dec 2007
Posts: 7,987
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From: Boise, Idaho
I found my intake/carb setup on craigslist. It's usually just the luck of the draw. Your call on Ebay though, but it could save you a couple hundred dollars.
$250 - $300 to put it all on is a fair deal. If he's going to tune all the jets for you for your engine while he's at it, it's an excellent deal.
You're not going to know what hit you after you drive it out of your mechanic's shop. This setup changes them into a whole different beast.
$250 - $300 to put it all on is a fair deal. If he's going to tune all the jets for you for your engine while he's at it, it's an excellent deal.
You're not going to know what hit you after you drive it out of your mechanic's shop. This setup changes them into a whole different beast.
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Elder User
Joined: Sep 2005
Posts: 647
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From: Brumley, MO
Yeah I know I'll probably hurt something, like the clutch. I need to drive it a lot more and get more used to it before I do the swap, but I gotta save a little money anyway so thats what I'll do while I save money.
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Joined: Dec 2007
Posts: 7,987
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From: Boise, Idaho
What transmission does it currently have in it? Most of the transmissions in those were designed to bolt up behind the big V8s, so they should be okay. None were really 300 exclusive. Unless it's the SROD (aluminum 4 speed manual with overdrive and a push down reverse, which I have bolted behind mine), most anything should withstand whatever you throw at it.
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Elder User
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From: Brumley, MO
It's either a NP435, or a T-18, not sure which one, but it's a cast iron 4 speed with a granny gear. BTW did you notice a difference in exhaust sound after the EFI manifold swap, because my buddy thinks my motor sounds like a V8, and he hates any thing that sounds a little ricey, so that was a compliment for sure.
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Joined: Dec 2007
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From: Boise, Idaho
You've got nothing to worry about with either of those trannies, unless there's something already wrong with them. 
As for sound, it's hard to say what affected what since I replaced everything from the block back. Went from the stock manifold, 1 7/8" exhaust, SUPER plugged cat, and a rotted out old muffler (also plugged with chunks of the cat), to the EFI manifolds, 2.5" exhaust, high flow cat and turbo muffler.
YouTube - 1981 Ford Bronco 300 Straight Six new exhaust
It sounds even better now after it's been broken in. Nice,deep, and throaty. A lot of it will depend on the muffler you chose though.
As for sound, it's hard to say what affected what since I replaced everything from the block back. Went from the stock manifold, 1 7/8" exhaust, SUPER plugged cat, and a rotted out old muffler (also plugged with chunks of the cat), to the EFI manifolds, 2.5" exhaust, high flow cat and turbo muffler.
YouTube - 1981 Ford Bronco 300 Straight Six new exhaust
It sounds even better now after it's been broken in. Nice,deep, and throaty. A lot of it will depend on the muffler you chose though.
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