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post #1 of (permalink) Old 04-11-2000, 06:44 PM
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replacing 351 with an I-6 300

I just starting reading this board a few weeks ago. Now, I have a question.

Is it feasible to replace a junked 351w with an I-6 300? I see someone has one that is hitting 300 pds of torque, which is enough for me. Mainly, I want some gas savings if possible. I had an I-6 in my 1980 E-150, many years ago, and it had some good low end grunt and decent gas mileage. I will drive it 25K per year and when I need the power the most it is usually off-road in woods or plowing at low speeds.

I have a 1985 Bronco (just bought - has a blown up motor and is trashed body wise), 351w, C-6, NP208f, 9 inch rear with 3.50 gears. I want low end grunt to make it up steep inclines or out of muddy ditches along with decent gas mileage, 15 mpg would be great. 0-60 rubber burning is not a priority. I have a Ranger for that :-D

Any in sights? Will the I-6 give me any significant gas savings?




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post #2 of (permalink) Old 04-11-2000, 08:06 PM
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Re: replacing 351 with an I-6 300

Got an inline six in my Bronco and it doesn't do bad. It has been modestly built and gets between 12 and 13 MPG. Fuel injection would add another couple of miles. I have a 600 cfm Holley 4 bbl carb on it now. There is 16,000 miles on the engine and the reliability is there. It has torque like a work horse. I have about 350 lb-ft at 1800 RPM. If I had even a smaller carb than the 600, my mileage would be better, but the price goes up for anything other than the 600 cfm carb. Jet a 390 or 465 cfm carb and it would run perfect. My engine can do anything that 351 can do. I did a tug-o-war at a jamboree and did pretty good due to the fact that I could grunt them out, where they had to wind up the small blocks a bit. She ain't no big block, but it can feel like one at times. It will tractor up anything. I have the granny geared 4 speed in my Bronco (NP435) and I can let it idle and I can dump the clutch as fast as I can and the engine won't die. It will jump real good, but it will keep running. I have the carb set up now to where it could almost run upside down. Let me know if you want details on the engine.

If it ain't broke, I can probably still fix it.
post #3 of (permalink) Old 04-12-2000, 05:54 PM
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Re: replacing 351 with an I-6 300

<font color=purple>The cost of converting from a 351W to a 300 I-6 would buy an awful lot of gas. It'd probably be cheaper to fix what you have & trade it against a 6-cylinder truck.</font color=purple>

TEX

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post #4 of (permalink) Old 04-12-2000, 06:17 PM
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Re: replacing 351 with an I-6 300

Actually, I bought it for $100, so I feel sorta free to do what suits me :> I just want to know exactly what it is before I start ;D

I work at a Ford dealer (lowly lube tech for right now) and have access to tools, parts, and help if (when) I need it.

Will a swap entail more than a bellhousing swap and new relocated motor mounts?

post #5 of (permalink) Old 04-13-2000, 09:55 AM
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Re: replacing 351 with an I-6 300

Here are the tricks to the swap. You will need a radiator out of a truck with a straight six. The inlet and outlet are on opposite sides of the V-8 radiators. New motor mounts for the straight six. No other bracketry will be needed for the motor mounts. You will see when you get them. Make sure you get all of the accessory brackets for the 300, the brackets on the V-8 won't work. The alternator and P.S. pump should fit though. Get hoses for the 300 and with the correct radiator, they will fit perfect. For external parts, you can say the correct year of your truck (1985) and say it is a 300 straight six and you will get the correct parts most of the time. Some internal parts will be date specific. A few wires may need to be shortened or lengthened, but I wouldn't worry about that now. Good luck, Eric.

If it ain't broke, I can probably still fix it.
post #6 of (permalink) Old 04-21-2000, 10:11 AM
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Re: replacing 351 with an I-6 300

well since you got the I-6 truck I'm sure you have the motor mounts and radiator to go with it. Bone stock I got 15mpg with my 83' bronco with a 6 popper and 4speed. I've had 2 80's broncos with 351w and never seen better than 10mpg . I now have a beefed 6 popper and love it, I finally got it dyno tested and it puts out 205 hp and 310ft-lbs. of torque (stock 121hp and 232ft-lbs.) with a offenhauser intake, 600cfm edelbrock card, hooker supercomp headers, 9.2:1 compression, intake port matching, and a Torquey camshaft (compcam 260H cam). but my milage has droped to about 12 mpg with 3:50 gears and 33" thornbirds. my zero to 60 is around 9-10 seconds and My quarter mile droped from 22 second to about 18 seconds. and in the mud NO 302 can chug along at 500RPM like a I6

Do'n it with only 6 cylinders!
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