Johan.  You may already have the information for decoding the vehicle data plate located on your engine compartment's firewall.  IF not, click the link below for a good breakdown of the information the data plate provides.
http://www.ctci.org/decoder.php


NoShortcuts
a.k.a. Charlie Brown
near Syracuse, New York

Johan.  Back to your original cylinder head question that started this thread...

I was looking for information regarding a question Ted Eaton asked last evening about '55 Ford and Mercury 292 cylinder heads.  While I did not find an answer for Ted's question, I located this reference information for you when referred to it from the Classic Thunderbird Club International entry on page 26 of their 'Thunderbird Restoration Details and Specification Manual'.

The information is contained in Ford Service Letter #973, issued 01/25/'55.  It's titled 'Cylinder Head Identification (1955 272 and 292 Cubic Inch Engine)

Installation of the correct cylinder head is extremely important.  If the incorrect cylinder head is installed, rough engine operation will occur.  To ensure installation of the correct cylinder head or to check the cylinder head installed, use the identification given in table 3.  (-info without diagram included here...)
The picture shows measuring the pads described below.  For the '55 T-Bird 292 head the pad should read between 0.999 inch to 1.001 inch)

The 292 cubic inch Thunderbird and 272 cubic inch Special heads (early production) can only be identified from each other by the thickness of either of the two center machine locating pads (fig. 7).  The center pads are located directly below the No. 2 and 3 spark holes on the right-hand cylinder head.  On the left hand cylinder head, the pads are located below below the No. 6 and 7 spark plug holes.  The measurements given in fig. 7 (info. abbreviated and included below) can be used to identify these two cylinder heads either on the car or on the bench.  Late model 272 cubic inch Special heads may be identified by the number ECG-6090-A on top of the head.

The Cylinder Head Identifications in Table 3 indicate the original Ford Part Number, the Engine (application), the Compression Ratio when used on the 292 engine, and the cylinder head Identification information.  -Some of the info in the chart does not apply to other than the '55 'Bird 292 engine, so I'm going to skip listing it.  Here's the short of what you desire to know

292 T'Bird w/ Standard Transmission   -   8.1:1 compression ratio   -   Identification...
-  ECL-6090-A cast in top of the cylinder head

292 T'Bird w/ Fordomatic Transmission   -   8.5:1 compression ratio   -   Identification...  
-  ECL-6090-B cast in the top of the cylinder head

IF your cylinder head identification coincides with this Service Letter info., you're all set.

In another thread, this is what Oldmics turned up in the documentation he had available to answer Ted Eaton's question about '55 ECK-C cylinder heads.  Other '55 heads are mentioned in his article.  Click the link below.
http://forums.y-blocksforever.com/FindPost129376.aspx

Hope this info. resolves your original question.  

Charlie


NoShortcuts
a.k.a. Charlie Brown
near Syracuse, New York

Johan.  '55 'Bird engine shared information...

'55 and '56 'Birds and passenger cars with y-block engines used an ignition advance system tied to a LoadaMatic distributor.  An engine vacuum signal sourced from the carburetor throttle body provided a signal that advanced or retarded the firing of the engine's spark plugs depending upon engine speed (throughout the rpm range) and load conditions.  This system can be problematic due to its design, age, vacuum leaks, or defective diaphragms located on the carburetor base of the Holley 4000 ('spark control' valve) or the vacuum diaphragm chamber attached to the FoMoCo LoadaMatic distributor.

In '57, Ford changed from a full vacuum controlled ignition advance distributor to a combination centrifugal advance AND vacuum advance distributor.  IF your Mustangs were '60s or pre crank trigger, you're likely familiar with this set-up.  Many 'Bird enthusiasts have moved to replace their original '55 or '56 tach drive LoadaMatic type distributors with '57 'Bird tach drive distributors for reasons of drive-ability or reliability.  This changeover has driven the selling of '57 'Bird distributors to an insane level.  In attempting to help an acquaintance in acquiring a '57 'Bird distributor I was directed to buy one that had JUST been listed on eBay and was being 'watched' by 22 people.  The seller offered the option of bidding on the item or paying a 'Buy-It-Now price of $400 + dollars.  UGH!  I got it for him, but will not brag about having done it.  Click the link below to view the '57 'Bird distributor I obtained on eBay...
http://www.ebay.com/itm/1957-FORD-THUNDERBIRD-TACH-DRIVE-DISTRIBUTOR-ORIGINAL-UNMOLESTED-/332148411972?_trksid=p2047675.l2557&ssPageName=STRK%3AMEBIDX%3AIT&nma=true&si=fx4rbCmGGQ%252BPbhHzMikxHvDVbpI%253D&orig_cvip=true&rt=nc
Note:  1) you'll have to scroll down on the eBay page that opens; 2) this distributor was 'molested', someone had added another distributor plate atop the original '57 ball bearing distributor plate.  -Reason yet to be determined.  3) Charlie Brown doesn't think that '57 'Bird distributors are worth the money they are bringing!  BUT, I'm not a purist, either.

Consider swapping out the '55 'Bird distributor and utilizing a '57 to '64 FoMoCo later style y-block passenger car or truck distributor (w/o tach. drive).  IF you elect to use the later distributor with your '55 'Bird Holley 4000 carburetor you could disable the vacuum advance mode of the later distributor by plugging the distributor diaphragm canister port and removing the vacuum line from the carburetor base and plugging the outlet port and removing the 'spark control valve' and plugging that port on the passenger side of the carburetor base.  -A Holley 4150 / 4160 carburetor power valve block-off plug has the correct thread for accomplishing this.  IF, instead, you want to retain the original Holley 4000 carburetor and have it provide the correct vacuum signal for the later distributor you can follow the steps outlined in the following article by Ted Eaton.  Click the link below...
http://www.eatonbalancing.com/blog/2013/03/02/modifying-the-holley-teapot-four-barrel-carb-for-late-model-distributors/

Food for thought.    


NoShortcuts
a.k.a. Charlie Brown
near Syracuse, New York

Johan.  Miscellaneous 'Bird body thoughts...

1955 and early '56 'Bird frames were made of a thinner gauge of steel than later '56 and all '57 'Bird frames.  To 'beef-up' the early '56 'Bird frames, flat stock (my recollection) 3/8 thick x 1 1/2 wide was added to the bottom of the '56 frame rails for additional strength.  The continental wheel mounted on the rear of the '56 is said to have required Ford to stiffen the frame.  Change-over on the '56 frames occurred in February of '56.  Check your '55 frame for soundness in the vicinity of the front mounts of the leaf springs on both sides.  Look for cracks or holes on the bottom side of the frame in this area.  Tapping the area with a body hammer pick end also works well...

'55 Bird door posts had no protection from the weather and road throw-back from the front wheels.  Lift on the end of the mounted doors to determine that the door posts are 'solid'.  '55 door posts had two holes for door hinge attachment.  Door posts are critical components in 'Bird structural integrity.  It has to do with how the inner front fenders, outer front fenders, inner rocker panels and outer rocker panels are ALL spot welded together.  N.O.S. '55 'Bird door posts exist.  IF you need these, let me put you in touch with an individual who has them.  '56 / '57 'Bird door post deflector panels are 'GooD' additions to consider adding in going through your '55.

Original N.O.S. rocker panels for the '55 through '57 'Birds still exist.  These are not cheap, but offer the best structural integrity to the body IF they are properly installed.  Again, IF you need these, let me put you in touch with an individual that has them.


NoShortcuts
a.k.a. Charlie Brown
near Syracuse, New York

Thanks. Yes, there is of course no way that a larger swept volume will give the same compression ratio if everything else is kept the same. I should be able to calculate the difference actually.
I am actually living in Sweden but also the Swedish Classic T-bird club recommends to join CTCI so that is on my agenda.

Thanks. Yes, there is of course no way that a larger swept volume will give the same compression ratio if everything else is kept the same. I should be able to calculate the difference actually.

Thanks again Charlie, very useful recommendations on literature. The Swedish Classic T-bird Club also recommends membership in CTCI so I will join to get access to all the knowledge there. This is my first Bird, previously it's been mostly Mustangs, so the questions are now increasing by the hour...
Yes I was confused that the same casting was listed to be used for two different bores and on top of that listed having the same compression ratio for the two different bores. Still not 100% sure if I have correct heads or not?
By the way, my Bird unfortunately did not escape New York in time and on top of that had some not so professional repairs done to it. The chassis had survived reasonably well, after all it is quite sturdy! But the body has required a huge amount of work to get it back in its original shape. The nice thing with the car is that it comes with a lot of documentation with original sales paper etc.

If I remember correctly, the "A"  head will produce a higher compression ratio on a 292 as compared to a 272.

You can buy the CTCI Restoration and Specifications Manual directly from CASCO.  However, you pay approx. 40.00 more.  You don't have to become a CTCI member.  However, I recommend you become a member of CTCI.  They have a very nice bi-monthly magazine full of early TBird stuff, including a Tech area.

Another suggestion is that you join a local TBird club.  CTCI has chapters all over the U.S..  Members can be an invaluable source for information and parts.  They also have yearly convention (early Birds only), sponsored by the local chapter.  One such convention is being held in New Jersey this August.  See  ctci.org for more information on the organization and the convention.

The manuals noted above are good sources for info.  One that wasn't mentioned (i didn't see it??) is the Electrical Assembly Manual which gives you excellent info on the Birds electrics.


54 Victoria 312;  48 Ford Conv 302, 56 Bird 312
Forever Ford
Midland Park, NJ

John's chart has a typo as there is no way a 272 will have the same compression as a 292 with the same heads.  It is impossible.  That is the reason for the confusion.


Lawrenceville, GA

Johan.  I'm looking for compression ratio info for your '55 'Bird.

In the mean time, here's some info that may help you in determining IF your heads are 'original' or IF the deck surfaces were re-machined in the past 62 years.  Too, once the volume of the combustion chambers is determined, IF you determine that you want to increase the compression ratio for your particular cylinder heads, it will help you in knowing how much to have the machine shop mill the head deck surfaces to appropriately reduce the combustion chamber volumes.

On the exhaust port side of y-block cylinder heads are a series of 'pads'.  These are located below where the exhaust manifolds are bolted on and adjacent to the spark plug holes.

When the cylinder heads were originally manufactured, the pads measured 1.000 inch thick.  IF the cylinder heads have been 're-surfaced', you can determine how much they were 'cut' (milled) by measuring what the thickness of the pads are now.  

Click the link below for an article written by Ted Eaton on calculating how much the compression ratio is changed by milling your particular cylinder head a particular amount.  Scan the article to see the listing of your heads on Ted's chart.
http://www.eatonbalancing.com/blog/2013/01/30/cylinder-head-milling-for-a-1cc-reduction/

Hope this helps.  


NoShortcuts
a.k.a. Charlie Brown
near Syracuse, New York