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1987 - 1996 F150 & Larger F-Series Trucks 1987 - 1996 Ford F-150, F-250, F-350 and larger pickups - including the 1997 heavy-duty F250/F350+ trucks

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Old Apr 17, 2025 | 11:16 PM
  #1  
Koda1293!'s Avatar
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NEED HELP!!!

I've got a 1990 f250 with a 7.5 and am attempting to convert it to carb from efi by taking the intake manifold from a carbureted 460 in a 86 motorhome and swapping it with my efi intake manifold.
I just want to make sure I'm doing it correctly and so far the only thing that I'm having an issue with is a small difference in the shape of intake ports.

As for transmission control, can I take the "sensor/kickdown" off the motor home as well ?
It seem like it is pretty much identical minus wire harness on the 1990.

Also. Can I now remove ecm and wire harn
 
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Old Apr 18, 2025 | 01:36 AM
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Does your truck have the c6 or E4OD transmission? The motorhome has a c6 which is a '60s era 3 speed mechanical transmission. Your truck probably has the 4 speed electronic E4OD transmission introduced in 1988. Two different animals. You'll still need to run the ECU in your truck to operate the transmission. That means you'll need the throttle position sensor and distributor for the rpm signal. Not the easiest thing to graft onto your carburator.

Have you considered just repairing your efi setup and not modifying the engine?
 
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Old Apr 18, 2025 | 06:34 AM
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Originally Posted by Koda1293!
I've got a 1990 f250 with a 7.5 and am attempting to convert it to carb from efi by taking the intake manifold from a carbureted 460 in a 86 motorhome and swapping it with my efi intake manifold.
I just want to make sure I'm doing it correctly and so far the only thing that I'm having an issue with is a small difference in the shape of intake ports.

As for transmission control, can I take the "sensor/kickdown" off the motor home as well ?
It seem like it is pretty much identical minus wire harness on the 1990.

Also. Can I now remove ecm and wire harn
What is wrong with the EFI system? I have read threads on this forum about the difference in cylinder heads that prevent you from slapping a carb intake on the EFI heads but I do not recall what was done.

What are your plans for the ignition and fuel systems?

Does the truck have an overdrive cancel switch on the dashboard? What about the motor home? Does it have a cancel button?

Originally Posted by Prototypemech
Does your truck have the c6 or E4OD transmission? The motorhome has a c6 which is a '60s era 3 speed mechanical transmission. Your truck probably has the 4 speed electronic E4OD transmission introduced in 1989. Two different animals. You'll still need to run the ECU in your truck to operate the transmission. That means you'll need the throttle position sensor and distributor for the rpm signal. Not the easiest thing to graft onto your carburator.

Have you considered just repairing your efi setup and not modifying the engine?
Fixed that for you.

Absolutely. I would fight my way through diagnosing and repairing EFI.
 
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Old Apr 18, 2025 | 06:44 AM
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I believe the intake and exhaust manifolds are different spacing for the carb'ed heads versus the EFI. I do not believe it is an easy swap.
 
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Old Apr 18, 2025 | 07:04 AM
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It's basically impossible without swapping heads
Never say never, but time is money
The intake ports do not match
Not sure about the exhaust ports, but the intake ports are a deal breaker for a 1986 engine swap to EFI
 
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Old Apr 18, 2025 | 11:53 AM
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The carb solution to EFI intake is here:

https://www.pricemotorsport.com/

Click on carb adaptors.

Everything else is on your own.

I'd fix the EFI.
 
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