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I've been contemplating heads and came across some interesting info. I pulled the numbers for a bunch of heads and ran them through a flow to horsepower formula. All the flow numbers are taken at .500 lift except for the last 2 which are all out race heads so I used .600 for those.

The optimum ratio of exhaust to intake flow is supposedly aound 80 percent. The horsepower numbers are calculated on intake flow under the assumption that the exhaust flow is optimum. I don't know how to fudge the horsepower down if the percentage is lower than 80 but I would assume it would hurt greatly. These horsepower numbers also assume there are no other blockages to flow like a choked up exhaust or too small intake/carb.

head.......................I......O.....ratio.theoretical hp estimate @ 80% ratio
289 stock heads.......168.118....70%.345*
E0 302's..................155.106....68%.319*
D0 351W's...............179.118....66%.368*
GT40P's..................196.138....70%.403*
Performer RPM's........214.171....80%.440
GT40 X305's.............210.160....76%.432*
Windsor Sr's.............221.146....66%.454*
Windsor Jr's..............186.148....80%.382
Trick Flow TW...........242.178.....74%.498*
Victor Jr's.................288.198....69%.592*
Trick Flow R's............335.230....69%.689*
* denotes heads that won't hit their theoretical potential
due to needing more exhaust work



You can see my 65 fastback at: http://hottarod.stangnet.com/
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hey, that's some nice work with the flow testing...i'm sure that it will come in useful for us the uneducated! :)

College Station, TX
 

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Best computer I know of is the ET clocks at the race track....they're never wrong...*G*

Seriously, I've always been incredibly lucky in getting good performance out of my SBF's and I've always just done the best I could with what I've had around.....
Even the RPM's on the race car are bone stock....

In the years I've run it, people are always amazed how well it does for as mild as it is/was....I always tell them to look at the whole package, not just any one part....

Of course, then there's the driver...*G*

Given the performance of the car, by your chart, the engine isn't completely utilizing the HP potential of the heads (I'm estimating 400 or so flexplate HP)...

Thanks for crunching the numbers for us...

Pat
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Good post Hottarod.

I too have been contemplating heads and that is some interesting info.
 

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Discussion Starter #6
AFR 165...74%...514 theoretical max horses
AFR 185...69%...549 theoretical max horses

If you take the percentages straight down 6% off the 165's is
31 horses and 11% off the 185's is 60 horses so out of the box they probably run just about the same.


You can see my 65 fastback at: http://hottarod.stangnet.com/
http://members.aol.com/macstang/Gifs/macstang3.jpg
 
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