Hi all, been a long time since I ventured into this section of FTE.

'79 Bronco with the '86 300cid still runs fine, but it's falling apart everywhere else, lol. I'm looking into doing a complete rebuild of this truck in hopes to make it good enough that my wife will consider driving it as her DD, lol.

So the question is this: MPG is essentially more important than overall power. Would I be better off converting the old leaky 1bbl Carter to Holley 4bbl and Offy DP, with a rebuild ($$$), or swap in a lower mileage mass-air EFI 300 (more forgiving to mods than a non mass-air) from '96? Either way, I'll be looking at converting to an OD tranny as well. So those with 4bbl NA 300's, and EFI 300's, with OD trannies, what kind of MPG are you getting?



I've never driven with OD, and my old 300 got about 12mpg w/C6 and NP203, and we live 15 miles from the nearest civilization, so it's always highway miles.

 

If its MPG that is important forget about the 4V and Offy intake. The EFI conversion makes sense. Better still, just rebuild the YF Carter - or get a good new one. It will give just as good highway fuel economy as EFI - maybe better since it is not constrained to running around stoichiometric 14.7:1, as is EFI. It could cruise at 15:1 or higher. My '83 van got 21 mpg highway. The EFI will have the best manners for cold start, etc. but will cost loads more than a carb rebuild and a tune up.

 

I happen to now own an 83 Van 300-6. I have just kitted the original carb..and will have it running again soon hopefully..question is..:

Do yo have an opinion about the AUTO-LINE C666 (manual choke version)..I have that in mind for my van if this rebuild don't quite cut it..I TOO have a worn throttle shaft housing. I have a feeling that for many guys running the YF or YFA.. a new carb recommendation would be appreciated...

Thanks for the butt-in patience.

 

I don't know about Auto Line products. Sorry

 

I'm putting an efi 300 into my 79 F150 right now. It's not that hard. Only real fab that needs to be done is a small clearancing mod to the A/C plenum where the lines come out. Building the wiring isn't that hard. Just make sure you get everything from the donor vehicle. The efi runs night and day better than a carb and gets about 17 mpg average. I drive a 95 every day and get that with a lead foot.

 

If you convert to EFI you will want to convert to an EFI cylinder head, which features a faster burn chamber design, Otherwise your spark timing tables will be off (too retarded).

 

havi,


See if this link will help?


https://www.ford-trucks.com/forums/1...-9l-300-a.html

 

I have a pretty big cam, and 4bbl. After getting the calibration kit for the carb, I now get 14.5mpg (with a stock 4 spd, and 2.75 gears). Not the best gearing for hauling or city driving, but not that bad.

 

Thanks guys, gives me something to go with.

 

my 74 2wd ext cab gets 16-18 with a light foot. The m50d-r2 tranny is garbage if u want to ever haul anything bigger than groceries. ZF transplant in the future.