I have two engines here with ECK-C heads.  Both are 1955 engines with one being out of a 1955 Ford police car with a standard transmission and the other being out of a 1955 Mercury also with a standard transmission.  Both engines are 292 and both have ECK-B blocks.
 
Not really related to the advertised HP numbers but here’s some info on the carbs.  Both have teapot carbs with the police engine having a ECK-T carb while the Mercury had the ECK-G carb.  Date coding both engines finds the Mercury engine being built five months earlier than the police engine so that jives with the carb numbers as both carbs are listed for both the 1955 Ford and Mercury 292’s.  The 1955 Thunderbirds had their own carbs and differed from these.  The difference in the two carbs I’m dealing with is apparently a revision of the main jets and the power valve sizes which was likely a normal deal during the course of production during 1955.  The ‘G’ carb came stock with #51 main jets and a 0.040” power valve while the ‘T’ carb came stock with #50 main jets and a 0.043” power valve.
 
The quandary here (according to what books I have) is the Mercury is rated at 188 HP while the Ford is rated at 193 HP.  The Mummert site lists the ECK-C heads as being 198 HP but I’m inclined to believe that’s the automatic transmission HP rating which should be another set of heads getting the compression ratio up around 8.5:1.  I reverse engineered the static compression ratio for the stock police engine upon disassembly and found it to be 7.6:1.  That comes close to my books saying that both the 188 HP Merc and 193 HP Ford 292 are listed as being 7.5:1 SCR.  I haven’t disassembled the Merc engine yet but will also reverse engineer the SCR and confirm that it’s in the 7.5:1 range as listed in some of my literature for the stick shift cars.
 
So my question is “What’s the correct HP number for a 292 with ECK-C heads?”

Lorena, Texas (South of Waco)

Ted
In Mummerts site you will notice that the ECK **** C heads are grouped in with ECL****B and ECL****C units.  All of which are slated for Mercury and T Bird applications.
I have documentation from the "National Service Data" books.

Under the Ford listings and in  the cylinder head section there is no specification or decree for the ECK****C head application used for the 1955 model year.
There is also no listing for head application in the Mercury section.

It does list under Ford as the heads used are ECL****A , ECL****B , ECK****B , ECG****A

In Mummerts listings your ECK****C heads are associated with additional heads speced with the same compression ratings.Those similiar compression heads are cast as  ECL****B and ECL****C .

Now the reason that I mention this is because of a notation in the National Service Data book regarding a differing cylinder head thickness measurements on the ECL****B heads.

It specs two differing  head thickness on the ECL****B heads. 
One is speced as .999 - 1.001 slated for  the 292 Thunderbird engine and the other is speced as .964 - .966 on the 272 Special (early) engines.

I"m thinking that since there was a "pool" of heads  (ECK****C, ECL****B , ECL****C ) , that were compression interchangeable that perhaps a pair of those ECK****C  heads (of yours) were cut to fullfill the ECL****B  -   272 needs but instead got installed onto your 292 engine upping your horsepower rating.

There was also a camshaft change that is noted as a  "material specification change only".
The early cam was cast as ECB and the later cast as ECK.
Might want to see if those cams are actually of the same event timing if they are cast as different critters.

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