I currently have a '91 F-150 with a 4.9L inline 6 cylinder engine. I am getting a 390 with a C-6 to swap this weekend. I plan on swapping the engines at the end of may. I was wondering if anybody could help me by telling me any modifications that i will have to make under the hood. THe engine is complete and ready to run. I know that I have top take the harnes from the old truck, and can throw out the computer i think. Do I still need the computer to control my fuel pumo or should I be able to run a mechanical pump? Any info would help me greatly. I would really appriciate it. Thank you for your time.

 

HEY MAN I WANT TO PUT THE SAME MOTOR, IN PLACE OF THE SAME ENGINE YOU GOT, EXCEPT MY TRUCK IS AN 86, THE BOYS ON HERE DONE TOLD ME ITS A PAIN IN THE ***, BECAUSE THE MOTOR WAS MADE FOR THE 70s AND EARLIER GENERATION TRUCKS, HE TOLD ME I SHOULD FIND A MTOR OF MY TRUCKS TIME LIKE A 302 OR A 351W 400, 460 YOU KNOW. IF I HAD THE TIME ID MAKE ALL THE FABRICATIONS TO MY TRUCK TO INSTALL A 390(motor mounts,tranny,etc.

 

P.S. NOTHING ON A 390 SHOULD BE COMPUTER CONTROLLED , JUST RUN A MECHANICAL PUMP.

 

So, your going from and EFI 300 6 to a carburated 390? Some other folks will have to answer the fuel pump question. There will be a difference in fuel pressure and gallons per minute between the electric pump and the mechanical pump and there may be some changing that needs to occur in the tank itself, but someone else can address that issue.

You will have to remove the perches that your 300 sits on and get new big block motor mounts. I would think that the transmission mount would be the same and the length of the tranny is the same, but there could be an issue that would require you to relocate the transmission crossmember and to shorten the drive shaft. That's something that needs to be checked out. Also, if you've got the entire engine, then you should have all the pulleys and brackets to mount your front accessories (power steering, A/C, altenator). You will have to work out a different throttle linkage, kickdown, and cruise control. Lokar makes kickdowns and throttle cables that you can cut to fit, or you may want to get that stuff from your donor vehicle. The radiator needs to be changed and you will need the transmission to radiator tubes that come with your big block application. Your 300 radiator will not have the cooling capacity needed to cool your 390 and the trans cooler as well as the hoses are mounted opposite of the 300 I6 radiator. You will also probably need a deeper fan shroud. Also, check to make sure that your oil pan is a rear sump or it will not clear the front cross member.

Well, that's all I can think of, Good luck,

Slik

'82 F150 2WD w/351W (orig 300 I6)
Slik