200-250 head swap

[Anonymous]

Im new so forgive if i beat a dead horse.

ive got a 65 ranchero with a 200 and 3 speed manual.

want to put on a 250 head with my rebuild.

ive found a rebuilt 250 head for 69-71 and one for 75-79

will these work on my 65 200 and what is involved with swap.

what is best head to go with the 69-71 or 75-79

plz help new to 6cyl engine want to get ride running with extra power..

 

[Guest]

Did you read the first topic on this forum? It will answer your questions.

Al

 

[Anonymous]

yes i read it and understand guess what i want to know ,what is the difference with the two heads if any?...is onne a better choice than other...like better valve sizes ext?

 

[Anonymous]

HI JOKER71,

WELCOME TO THE FORUM. YOUR QUESTION AS TO WHICH HEAD WOULD BE BEST REQUIRES UNDERSTANDING HOW TO READ THE CASTING NUMBERS. THE CASTING NUMBER IS ON THE TOP OF THE INTAKE MANIFOLD. FOR A 1969 HEAD IT WOULD START WITH "C9". A 1975 HEAD WOULD START WITH "D5". THE LARGE VALVE HEAD IS THE "D7" AND LATER HEAD. "D" MEANING BUILT IN THE 70'S, AND "7" BEING THE YEAR. D7 = 1977 HEAD. IN 1969 ("C9") TWO VERSIONS OF THE HEAD WERE BUILT. ONE WITH A 1.5" CARB MOUNT BORE AND ONE WITH A 1.75" CARB MOUNT BORE. THE 1.75" HEAD IS THE BETTER CHOICE. THIS WOULD BE THE C9 XXXX M HEAD. LAST LETTER OTHER THAN "M" IS THE 1.5" BORE. FROM THE C9M UNTIL THE D7 THERE IS LITTLE DIFFERENCE IN THE CASTINGS. D7 AND LATER IS THE LARGE VALVE HEAD, BUT THE LARGE INTAKE VALVE CAN BE INSTALLED IN THE EARLY HEAD.

HOPE THIS HELPS - STEVE

 

[Anonymous]

thank you for the info..helps alot.

ok one more dumb question and i think i got it.

if i get a 250 head i have to mill down to keep my CR and know it is better to have the bigger carb port in intake.

but if i took my 200 head and had the carb hole drilled to 1.75 and bigger valves put in with all the valve work done and port/poilish job done in the end what is the advantage the 250 head has over my 65 200 head?

thanx for all your help.

 

[61Futura]

The intake log is larger also. It will flow more cfm. About the compression ratio, the 250 heads combustion chamber is probably 10cc larger. You'll have to mill .050 from the head and block for the difference. The newer head gasket difference will want another .020 or more. Milling a total of .070 has me concerned since I am planning on putting a C9-M head on a 200 that has a C7-D head on it now.