Thread: Ford 300 six

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I'm considering locating a 300 six to replace the gas pig 390 in my 73 F250. Does anyone know if the original C6 will bolt to the 300? Flexplate? Converter?

I'm pretty much fed up with 8 miles per gallon in a daily driver.

Thanks for your help.

Hey tech. I know that the same transmissions were put behind ford 300s as 302s and 351s, so there shouldnt be any reason that the 300 wouldnt bolt in. As for the convertor and flexplate, use a 302 piece if they wont fit with the stock 300. Hope this helps

Originally posted by drg84
Hey tech. I know that the same transmissions were put behind ford 300s as 302s and 351s, so there shouldnt be any reason that the 300 wouldnt bolt in. As for the convertor and flexplate, use a 302 piece if they wont fit with the stock 300. Hope this helps

i think the 6 cyl. was by itself. they used C4's and you had to change the bellhousen to make them work. i think. dont belive the C6 will bolt up to the 6. just a flash back i had, could be wrong.

Hey Tech Inspector! Sounds like you're going to opposite direction of what I'm working on. 428CJ in a '65 F100 that had the 300 (transplant from a 1975) and three on the tree.

As far as I've been able to tell, the bell housing is different from the C6 to the I6 bolt pattern. If I could get away with it, I'd just put a heavier clutch in the F100 and stick with the 3-speed, but I don't think that old gearbox would hold up.

Someone may make an adapter plate or some such, but I don't think I'd trust it. I'd just try to get the 300 and its matching trans, and store (or sell) the C6. I've checked Summit Racing, and the FE blocks show a unique set of transmissions - don't work with the small blocks or Lima motors.

The C4 does show separate bellhousing, while the C6 is integral. God luck with it.

Just re-read your initial post - hadn't remembered it was an F250. Not sure what they did for trans in these. The C4 is a little light duty - there may be a C6 for it, but I still don't think the FE bolt pattern will work.

Hey Denny! Looks like you have illustrations of all the wierd Ford stuff. Thanks for the info - a picture's worth a thousand words and all that.

Do you think the '65 three speed from an I6 will hold up to the four twenty whatever I've got? I'm sure I can find a 352 bellhousing somewhere...

390 is an FE engine with a bolt pattern all their own. The 300 six uses the same pattern as 289,302, 351W, and 240 six. Flex plate is different, too. The converter should work.

"I'm pretty much fed up with 8 miles per gallon in a daily driver."

Yep that's about right for a 390. The 300's were great motors (came standard in F-600's) BUT, they were never known for fuel economy. As I remember, a 300 would get about 10 to 12 MPG. A 302 would probably be a better choice for economy.

If your heart is really set on a 300 check out the last few years production with the big plenum and fuel injection. Plenty of torque,and very respectable mileage. You could also go diesel,with the 7.3 being far better than the earlier 6.9.

I agree with Dyno, if you don't really have your heart set on a 300, the 302 would probably make better mileage. Or my fave, a 351W! The Windsor should get double the mileage of the 390, with lots more power than the six. just be sure to get the complete motor/trans setup from the same donor car (or truck) to avoid balance problems.

Overdrive, if your engine's good.

A C6 from a small block ford(windsor) motor will bolt up. As for the converter, check with your local transmission parts house. The one from the 390 could have the wrong stall. The wrong stall converter will cause it to run terrible.

As said before, it will need to be a small block C6(302,351W). I pulled the 351W out of my E350, and put in a turbocharged 300 six, and it bolted right up, except the motor mounts of course. But, I decreased mpg with the turbo, I use to get 11 mpg's with the 351, it dropped to 9 mpg's with the 300 six. But it had more torque than a diesel!

get a '87-'95 F150 300 I6, fuel injection and they get fairly good gas mialage, my grandfather got 18 MPG with his '88 5spd 4X4 and with his '95 2wd auto, he gets 20-22 MPG. save the truck's brains and pick up the engine at most any junkyard.