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351W to 300 I6 Swap?

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prodirt6000
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351W to 300 I6 Swap?

Post #1 by prodirt6000 » Wed Dec 02, 2015 6:53 am

Hi everyone,
I'm new to this site and hope this is the spot to ask the question. I have been trying to do some research on google and other forums about swapping motors in my truck.

I have a 1989 F250 EFI 351W with C6 transmission and 4:10 gear ratios. I have spent time and money going through the whole thing with complete tune up, timing, fluid changes, checking all my brakes, you name it. I cant get better than 5 mpg. I brought it to an old Ford mechanic and he says there is nothing more that can really be done. It just smells rich all the time. My grandfather has an old 1985 plow truck F250 with a 4 speed standard and carb I6 that is not road worthy. He said I can have the truck and swap engines if I want.

I would like to keep my truck automatic. I know the C6 is power hungry and is part of the issue for my low mileage, but still I believe I can do at least 10 with the straight 6. From what I have read that engine should bolt right up to transmission .

Anyone know of this working or not? Worth the hassle? Will it pass emissions ok?

Thanks in advance!!

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bubba22349
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Re: 351W to 300 I6 Swap?

Post #2 by bubba22349 » Wed Dec 02, 2015 12:28 pm

:hmmm: Something doesn't seam quite right with some part or parts of the 351 W EFI system if it's too rich. They will do better then 5 MPG when everthing is working right, but the 4.10 ratios aren't helping you either. You need to find someone that's really good with the EFI emissions systems to look it over. As far as the 300 goes yes it will bolt to the C6 and into the truck you will need to get a 300 six C6 flex plate, the front engine mounts, and correct oil pan and pickup tube to fit into your chassis. i.e. Main difference is that a 4x4's oil pans are different then used in a 2x4. As to if will pass emissions test I seriously doubt it, but that depends on the emission rules in the state were you live. For example in Ca. you can't install an older carb engine in place of the later model EFI engine it would not even pass on the visual test. To me it would be be better to get a later model truck with 4.9 / 300 EFI engine 1987 to 94 along with its correct computer and wire harness to use for the swap, its also going to be a lot of work. Good luck :nod:
A bad day Drag Racing is still better than a good day at work!

I am still hunting for a project car to build but with my current low budget it's not looking so good. My Ex- Fleet of Sixes these are all long gone! :bang: 1954 Customline 223 3 speed with O/D, 1963 Fairlane project drag car with BB6, 1977 Maverick 250 with C4, 1994 F-150 a 300 with 5 speed.

prodirt6000
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Joined: Tue Dec 01, 2015 4:57 pm

Re: 351W to 300 I6 Swap?

Post #3 by prodirt6000 » Sun Dec 06, 2015 4:22 pm

bubba22349 wrote::hmmm: Something doesn't seam quite right with some part or parts of the 351 W EFI system if it's too rich. They will do better then 5 MPG when everthing is working right, but the 4.10 ratios aren't helping you either. You need to find someone that's really good with the EFI emissions systems to look it over. As far as the 300 goes yes it will bolt to the C6 and into the truck you will need to get a 300 six C6 flex plate, the front engine mounts, and correct oil pan and pickup tube to fit into your chassis. i.e. Main difference is that a 4x4's oil pans are different then used in a 2x4. As to if will pass emissions test I seriously doubt it, but that depends on the emission rules in the state were you live. For example in Ca. you can't install an older carb engine in place of the later model EFI engine it would not even pass on the visual test. To me it would be be better to get a later model truck with 4.9 / 300 EFI engine 1987 to 94 along with its correct computer and wire harness to use for the swap, its also going to be a lot of work. Good luck :nod:



Thanks for the response. I have checked everything over on my truck and had a Ford guy look it over that multiple people recommended. Everything I do nothing works for the truck. 5 mpg max. Its killing me. I would be happy with 10. The donor truck with the 300 I6 is 4x4, as well as my truck. Besides the flex plate, would that truck have everything I need on it to make the swap? Oil pan should work since both 4x4? Here in Vermont I dont know what the laws are specifically, I know as long as its under 1996 and no check engine light, they dont bother hooking it to a computer or anything. On my other 1994 and 1995 trucks they just jack up the front end check the tires and lights and slap on a sticker. I was hoping to use this donor truck and go to carb since it was all free.

Thanks again.

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bubba22349
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Re: 351W to 300 I6 Swap?

Post #4 by bubba22349 » Sun Dec 06, 2015 5:09 pm

Yes if they are both 4 x 4 trucks it should be a fairly straight forward swap. Well sounds like you could get away with using the carb engine in your state. You will also need to use the 351W starter with your 300 to fit the C 6. Good luck on the swap :nod:
A bad day Drag Racing is still better than a good day at work!

I am still hunting for a project car to build but with my current low budget it's not looking so good. My Ex- Fleet of Sixes these are all long gone! :bang: 1954 Customline 223 3 speed with O/D, 1963 Fairlane project drag car with BB6, 1977 Maverick 250 with C4, 1994 F-150 a 300 with 5 speed.

prodirt6000
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Posts: 3
Joined: Tue Dec 01, 2015 4:57 pm

Re: 351W to 300 I6 Swap?

Post #5 by prodirt6000 » Wed Dec 09, 2015 7:28 pm

bubba22349 wrote:Yes if they are both 4 x 4 trucks it should be a fairly straight forward swap. Well sounds like you could get away with using the carb engine in your state. You will also need to use the 351W starter with your 300 to fit the C 6. Good luck on the swap :nod:


One last question. I talked to a mechanic and he said it will pass inspection fine as long as there is no check engine light. Will doing this swap cause that and if so how can I avoid it/correct it?

Thanks!

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bubba22349
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Re: 351W to 300 I6 Swap?

Post #6 by bubba22349 » Thu Dec 10, 2015 12:35 am

Yes it will. The check engine light is connected to ECU, so you would need install the complete top end parts from an 1987 to early 95 4.9 EFI engine, i.e. The upper and lower intake, exhaust manifolds and y pipe, the 4.9 engine and ECU wire harness, the ECU (computer) from a 4.9 with a C6, all the sensors, etc. that would be a big job. :hmmm: Then of course a burnt out bulb also won't light. Good luck :nod:
A bad day Drag Racing is still better than a good day at work!

I am still hunting for a project car to build but with my current low budget it's not looking so good. My Ex- Fleet of Sixes these are all long gone! :bang: 1954 Customline 223 3 speed with O/D, 1963 Fairlane project drag car with BB6, 1977 Maverick 250 with C4, 1994 F-150 a 300 with 5 speed.

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