C9DE-6090M HEAD

[terryst]

I was checking the info in the Preformance Handbook and seen where the head that I have should have 1.649 intake valve dia and 1.38 exhaust dia. and combustion chamber volume of 51-53 cc

Upon disassemble it looks to me that the valve size are 1.75 and 1.38 and when I measured the combustion chamber volumes with atf fluid I was getting 62 cc in each cylinder.

Does 62 cc and the valve size look right to you guys or did I not measure correctly.

Head number C9DE-6090M
BLOCK NUMBER C5DE-6015H

 

[Anonymous]

That head is from a 250 engine - not original to your '65. More than likely, the previous owner had it rebuilt with available valves (the larger 1.75 INT). 52ccs sounds too small to me also. I have the same "M" head and it also has chambers around 60ccs. It also had the smaller valves as mentioned in the handbook.

Those larger chambers are hurting your compression ratio. If you are rebuilding, consider milling the head and/or using thinner original style steel-shim head gasket.

 

[falcon fanatic]

I also have the same head sitting on my bench. The chambers are 63cc and it has the smaller intake and exhaust valves. I've been porting it and I plan on installing the larger size valves and running a set of factory style ratio rockers. I'll probably use the basic stainless replacement valves from FSPP.
I'm also going to mill the log flat to direct mount my weber 38. I'm not sure what the chambers on my current head are, but I plan on milling this one down to 1 or 2 cc less than on my stock head. I figure I'll end up around 52cc.

 

[Anonymous]

what would teh compression be on that then?

 

[CZLN6]

Howdy Terry and All:

Terry, Please let me know the reference in the FPH, Page and edition. Recheck the chart on page 6. I'm working from the 7th edition. Please note that there were a variety of C9 castings with various suffixes. It was our original conclusion that the "M" castings were used on the "new for '69" 250 engine. A huge deck clearance and larger 62 cc chamber heads had the CR down to 8.2:1. Since, we have narrow evidence to believe that "M" castings found their way to 200 engines as well. To maintain CR on the 200s the chamber volume had to be reduced. That might explain the chamber size on your "M" head. It is even possible that one of these heads made it back to the 250 engine side, for a higher CR 250.

The other C9 castings, C,F,J, & K, were designed for the 200s and had the 52 cc chambers. They also have a round log and a 1.5" carb hole.

FoMoCo was famous for using the "Empty Bin" policy in making changes. This is expecially true in the early '70s when EPA requirements were coming, hot and heavy. Consequently, it is very risky to use adjectives like, "Always" and "Never" with vintage FoMoCo vehicles.

We have never seen an original "M" head with 1.75" intakes, which leads me to believe that your head has been up dated in it's 35 year history. Did it have the original FoMoCo steel shim head gasket? Or a Composite type? It it have hardened seat inserts? or any other evidence of machining?

This is also a good reminder to measure everything for yourself, twice! Carefully!

What a nice mystery!

Adios, David

 

[terryst]

Did it have the original FoMoCo steel shim head gasket? Or a Composite type? It it have hardened seat inserts? or any other evidence of machining?

David,I was looking on page 6 of the fifth edition of your book and you were right about the size for a 200.I was referring to the 200 65-73 head specifications.I have a 69 head on my 200 6cyl. The intake bore is 1.75 as stated on the head identification page between pages 52 and 53.

The engine did have a steel shim head gasket .I now know why I was getting low cr with this type of head (62 cc combustion chamber)on the engine.Also the head has adjustable rocker arms that I would thing someone used off a different head than the c9de

Thanks for all the help everyone has given

 

[CZLN6]

Howdy back:

Another clue that someone has been doing some mix-and-matching. Will you be using a shim gasket when it goes back together? Reread the sticky at the top of this forum for details on compensating for the different head and if needed, head gasket.

Adios, David