75 250ci General Questions

[dudeigota66]

I was looking through the classic inlines tech page but couldnt find the size of a 75 250 head. I see it ends at 74 and then picks up at 77 so im not sure of its size. Anybody know its size?

Would this be worth rebuilding with performance in mind in comparison to an 80's Fairmont 200 head?

Also did these have 1100's on them?

And this 250 has a three speed would it be the same 3.03 that was on the 200? Im thinking of putting it behind my 200.

Thanks Guys

 

[bmbm40]

I think the 80's head has bigger intake volume, bigger intake valves and ok for unleaded gas. May have had a Carter carb. Not sure about the trans. Get a copy of the Falcon Performance Manual, will answer all that stuff.

 

[tri-power 250]

dudeigota66, On the top of the log intake is there a D7xx cast on it? If so, I believe you have the same head as the 77-80 flat top of log head. The 77-80 hexagon shaped log is distinct. My 76 has the D7xx casting, which is the flat top of log head.
Ken

 

[dudeigota66]

Would the difference between the 80's head and the 75 head be enough to discourage the rebuilding between one or the other? I wanna get the most bang for my buck here and want to know if the 180cc difference between the 75 head and the 80 head be noticeable enough.

Im looking to build an engine with mean take off and strong highway power for regular street and above average muscle on the highway. Im gonna put a t5 behind it and want to be able to downshift that sucker and have her purr down the lane.

 

[CZLN6]

Howdy Bck:

Dude-
Q- "but couldnt find the size of a 75 250 head. I see it ends at 74 and then picks up at 77 so im not sure of its size. Anybody know its size?"
A- A '75 250 head will, most likely have 1.69 intake valves, 62 cc chambers and, assuming it is an "M" casting, a flat topped log with a volume of 1240 ccs. It may or may not have induction hardened intake valve seats.

Q- "Would this be worth rebuilding with performance in mind in comparison to an 80's Fairmont 200 head?"
A- An '80 casting will have 1.75 intake valves and hardened seats all around. The intake tract volume is 1,420. the chamber volume is 62 ccs.

Q- "Also did these have 1100's on them?"
A- a '75 250 would, most likely, have a Carter YF. An '80 head will, most likely, have a Holley #1946.

Q- "And this 250 has a three speed would it be the same 3.03 that was on the 200?"
A- yes.

Either head will work. I'd choose the '80 casting because it already has the larger intake valves. Either head will need to be machined to your CR goal. Either head can be modified for a larger carb. To meet your performance goal, you will need a combination of parts and machining; a performance cam, higher compression, well tuned ignition, more carb, improved exhaust, and better gearing. The head alone won't get you there, but is is a foundations for the rest of the story.

Adios, David

 

[dudeigota66]

Alright, Hopefully no one beat me to the 80s head. Its currently hiding in the trunk of some forgotten thunderbird in the corner of the lot.

Thanks alot for the posts guys. Now im gonna put things together for ma honey. 8)