What is the flow ratio of FE heads? (Percentage of exhaust to intake flow)

 

This site has some interesting info:
http://users.erols.com/srweiss/tablehdc.htm#Ford

Steve

 

All them #'s are nice, but they fail to tell you what the specific combos they were tested with. You can't really compare 427 highriser heads to a set of C8AE-H heads bolted on a 390 . The highrisers don't work on a 390 bore. Another thing I noticed is the #'s between the C8AE-H's and C4AE-G's. Supposedly the medium riser heads flowed better than the lowrisers, which the C8's have the medium riser ports and the C4's have low riser ports, and they're showing the opposite to be true.Another was the difference between the 289 Hi-po heads and the std 289 heads, they both have the same ports and valves, but they showed them to have different flow #'s , that just doesn't add up.

 

I'm thinking my heads are flowing in the mid to upper 70% range atleast. My heads were never flow bench but assuming there were all matched, I would benefit more from a single pattern, rather then the .548I(278deg)/.580E(290deg) that I'm running.

 

BTW, thanks for the clarification DuckRyder.

 

Just a note to tell you what Crane and Comp had to say.

I’m going to post to several threads that it seems apply to.

Crane said the 801 would work well in a 9.5:1 compression Iron head 390.

Comp on the other hand, recommended against the XE 274 on the basis that they thought it would build too high of cylinder pressure and have “pinging” problems. Said that the higher duration lower lift 280H would be a better choice.

The Crane and Comp appear quite similar on paper.

(and both are quite a bit hotter than the two discussed in this thread.)

I’m going to actually call him on Monday and discuss it further, but I thought it was an interesting turn of events.

 

I don't really care for the Crane cams tech support. They seem to have the best cam but the people on the other end of the phone seem clueless. They told me that if I didn't get rid of my HV oil pump that the distributor drive gear on the cam would wear off and that under no circumstances did any engine benefit from a HV oil pump. The 901 is too small for your build. I would go with the 941 or the 801. I wouldn't want a 901 cam in an engine with 10:1 myself. Cranking pressure would be pretty high. Detonation is likely with iron heads.

 

I would agree with the Crane tech, I'm partial to bigger cams myself.

 

Hey guys I'm a novice mechanic and learning more about the technical aspect of mechanical works.So how do you measure comp. ratios.
thanks jakes69

 

The simplest way to explain it, is to get a Ford Racing catalog and study their formula in the rear of it. Basically, you have to know the exact bore size, the stroke, the combustion chamber size, the deck clearance above or below the deck, the thickness of the head gasket, and the volume of the piston top, before you can figure the comp ratio.

 

I am building a 428 with the same cams and heads. I was wondering if you went with the 941 how well it worked out