A post on the 80-96 truck forum indicates some differences between the carb and EFI 300s, mainly in the head. Anybody know in more detail what those differences are? Also were there any significant changes in the engine from '65 to 86?

INLINE SIX POWER! '95 F150 XL
300 Cubic Inches of Low RPM Truck Torque! And twin-I-beams too!
"Drive a stick young man! There'll be time for automatics when you're old and unable."

 

I'm interested too.

 

They have different cams too.....

ftwfred

 

Carb head chamber:
http://www.clubfte.com/users/tetraruby/CarbHead.jpg

FI head chamber, notice the heart shaped profile:
http://www.clubfte.com/users/tetraruby/FIHEAD.jpg

 

The fuel injected motors also don't have the provisons cast in for a mechanical fuel pump. In my 81 I have a 300 out of a 96 f150 which i converted from fuel injection to carberated. I had to install an electric fuel pump and block off the holes on the right hand side of the head. Otherwise I have no problems other than if i leave the key on for too long without the motor running, it will flood.

 

Wow! Great stuff. Now we will wonder why the heart shaped combustion chamber as it would seem more restrictive for flow having less area around the valve. Also, wonder what the implications are for exhanging these heads between EFI and carb? Not that I am going to do any of this stuff--just intensely curious.

 

>Now we will wonder why the heart shaped
>combustion chamber as it would seem more restrictive for
>flow having less area around the valve.

It's for introducing swirl in the combustion chamber to speed the rate at which the mixture burns. More Efficient that way.

>Also, wonder what
>the implications are for exhanging these heads between EFI
>and carb? Not that I am going to do any of this stuff--just
>intensely curious.

Supposedly you need only 25 degrees total spark advance with that head, compared to 33 degrees or so for non-fast burn head. Also has smaller chamber that will give better compression. The closed chamber design also provides more quench area, which should make it less detonation prone at a given compression, etc. Has a coupla extra holes for mounting EFI intake.


The 87 and later blocks are supposed to have a different accessory bolt hole pattern. Early stuff will fit a later block, but there aren't enough holes on an early block for the later brackets.

65-66 engines took a main bearing with 3.403 diameter thrust on it. 67-on took one with a 3.602 diameter thrust. The early bearing cost twice as much. It will also fit the later block. The later bearing will not fit the 65-66 block, as is. I think a little trimming and it'll fit. I'm planning on doing that to an engine I'm re-ringing for cost's sake.

Other issues when swapping, they moved the dipstick around from year to year. And the clutch pivot holes may have changed.

 

 

i have a 1997 f150 with a 300 str 6 thinking about swapping to carb to put in a 1953 ford but didnt
know what i needed

 

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