Can anyone tell me how to tell the difference between large letter heads and small letter heads without having the two side by side to actually compare them? Or, better yet, does anyone have pictures of the two that could post them here? Thanks to all for the excellent information posted here!

Just for identification purposes, the location of the letters is an easy check.  The big letter, early style have the casting numbers near the exhaust ports while the small letter are a little harder to find.  On Mummert's website, he has pictures of where numbers are located at the top of the head identification page. The C pic is like big letter and the 113 pic is like small number.

Don

BamaBob.  Click the link below and read through the entries.  It should provide you with pictures, point out the orientation difference of the letters on the two different series of G heads, and give you the dimensions of the letters for the two different G series also.

http://forums.y-blocksforever.com/FindPost113734.aspx

Hope this helps.  


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

This is more of a question than a statement. Are not there posted and unposted g heads? Would that be an easier way to distinguish between the two?

Durham Missouri

62bigwindow.  There's three (3) species of ECZ-G cylinder heads that were used in car production year 1957 on y-block 272, 292, and 312 engines.  The large letter ECZ-G heads were cast in a different foundry than the heads with the small letter ECZ-G markings. 

Early '57 production year large letter G heads were un-posted until May of the '57 model year.  Commencing sometime in May 1957 (this is based upon casting date numbers) the large letter heads began being cast with 'posts' added to provide additional strength in the deck area.  Outwardly, to my knowledge, the un-posted and later posted large letter G heads cannot be told apart unless you look at the date codes under the valve covers.

None of the small letter G heads had 'posts' regardless of when they were produced during the '57 model year.  Again, these were produced at a different iron foundry than the large letter G heads.  What's always been amazing to me is that while the large G and the small letter G heads outwardly appear to be identical except for the casting ID, (AND the combustion chambers also appear to be identical, too) ...the small letter G heads were produced using different sand cores for creating the intake ports and the exhaust ports than what were used for making the large G heads.

What has registered with me when I've compared the two series of heads (large letter G and small letter G) is that the intake port flow into the underside of the intake valve appears to be 'better' shaped on the small G heads than on the large G heads.  Conversely, where the exhaust port exits the cylinder head to meet the exhaust manifold, the opening size is significantly smaller on the small G heads than the opening on the big G heads.

Personally, in doing porting work, for shaping purposes, I have historically preferred the small G heads even though they are not posted.
In the archives of our Forum are one member's step-by-step depiction and pictures of how un-posted heads can be appropriately posted.

Interestingly, ALL '57 'Birds were produced with 292 or 312 engines (except the supercharged 312s) that had large letter ECZ-G heads.  1958 Mercurys that were equipped with312 engines also had large letter ECZ-G cylinder heads that should have posted cylinder heads because of their production date.

Sooo... there are posted and un-posted large letter G cylinder heads and un-posted only small letter G cylinder heads.

Hope this helps.


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

A further note on the early small letter "G" heads. Our senior moderator, Ted E. says they should not be milled more than 0.025"  due to the thinner decks & no posts.


Paul

OK.  This is great info.  I was also wondering if ALL '57 G code heads were physically the same.  Some were cast at Dearborn others at Cleveland.  Specifically, was there anything special about the 312 G code heads that were on an E-Bird?  I ask since the G code heads could be found on trucks, Mercs, Fords, and T-Birds. A friend insists that the small letter G code head with (intake side cast) are specific to the T-Bird.  Is that correct?  Also, did T-Birds only use G code heads cast at the Cleveland foundry?

Welcome to the site, Matt.

Your friend is incorrect.  All C, D, and E code '57 Ford Thunderbirds came equipped from the factory with large letter ECZ-G cylinder heads.  No small letter ECZ-G cylinder heads were installed on '57 Ford Thunderbirds at the factory.  The information source to back this statement up is the Restoration Manual available from the Classic Thunderbird Club International, page 280 with picture #19 on page 281.  Also on page 280 is information stating that, 'All 1955-1957 original Thunderbird heads were cast at the Cleveland Foundry and have the foundry logo as shown.'  The reference is to picture #18 on page 281.

Consider re-reading what I posted previously in this Forum entry AND reading the link that was provided that references previously shared information on the topic in the Forum Archive.

The question you might have that perhaps was not re-visited above in this Forum entry is how can you tell IF the large letter heads that you might look at are later posted heads or earlier un-posted heads?  Casting date code would be one potential way, but the sure way is to look for the posts.

Click the link below, IF it wasn't already referenced, to get clear information on how to tell the posting status.
http://yblockguy.com/techtips/postedheads.html

Hope this helps.  


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

Matt.  Addendum to previous '57 Ford cylinder head information. 

ALL 1957 E code cylinder heads (passenger car and 'Bird application) used two piece valve springs (one spring w/ damper) and one piece valve spring retainers. 

ALL C and D code cylinder heads used one piece valve springs and a two piece valve spring retainers.  Both valve spring retainer systems used the same valve stem keepers.


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

When I first read your reply I panicked.  You see the person I was referring to is near completion in restoring an E-Bird w/ a 3 speed M/T.  I re-read your reply and thought about what he showed me on the head and other info he talked about.  Does it have the casting on the intake side, yes, and it's a Cleveland cast.  So, I wasn't paying particular attention to the size of the letter 'G', but rather the location.  My understanding is that the Cleveland cast heads were on the E-Birds, and that's really what to look for.  I also recall that he has the restoration book and is a stickler for detail.  BTW, I saw the car today and I must admit it turned out really nice.  Red with a soft top...not sure what color.  The engine bay is highly detailed.  I may share some pics if he gives me permission.