Can somebody please tell me how I can identify G Heads?

Thanks,

Ray

Somebody probably will post photos; in the meantime, search "Ford Y-block ECZ-G heads" and click on images. Unlike other Ford/Mercury Y-block heads, with the exception of 471 & 113 heads, the intake valve is noticeably larger than the exhaust valve. All Ford/Mercury Y-block heads have the same size 1.510 exhaust valve, but ECZ-G, 113, and 471 heads have 1.925 intake valves. 

There are essentially three different ‘G’ heads.  On all of these, the part number ‘ECZ-G’ will be located under the water jacket boss where the intake manifold bolts to the heads.  A picture showing that part number and where it is located will be in one of the links below.

The earlier ‘G’ heads introduced in 1956 are the small letter G heads and all of these are unposted.  The big letter G heads were introduced for the 1957 model year and those cylinder heads made at the Dearborn facility were all unposted.  The ‘G’ heads made after mid-May at the Cleveland facility were the posted variety.  Posts are an additional support added within the heads to minimize any flex taking place at the decks.  Whereas the earlier heads had the intake ports cast integral with the decks, the intake ports for the G heads were raised for increased flow which left an internal gap between the lower part of the port and the inner surface of the deck.  Hence the need for ‘posts’ when the compression ratio is increased and/or the heads are milled.

The service manual is very specific in not milling any more than 0.010” from the decks of the unposted G heads but I have been getting away with as much as 0.025”.  The later model posted G heads can tolerate milling the heads much more than this as I have gone as much as 0.070” and got away with that.

The following links will provide additional information and pictures.
http://forums.y-blocksforever.com/FindPost113735.aspx
http://forums.y-blocksforever.com/FindPost113752.aspx
posted vs non posted

Lorena, Texas (South of Waco)

What would be a fair price to pay fora pair of posted G  heads that are rebuildable?  Ray

Just finding a set of posted G heads can be a challenge. Pretty much all of the G heads I have seen, including mine, are non-posted. 

At the Thunderbird Extravaganza II event in the Sacramento area that I attended two years ago, a set of non-posted G heads was for sale for $600. They were bare heads that had been thoroughly cleaned by a machine shop & probably magnafluxed. I didn't stay long enough to see if the sold. I paid $125 or $175 for mine (can't remember), but that was 5+ years ago. Fortunately, they were within a reasonable driving distance. A bare head weighs approximately 49 pounds; shipping will be expensive, and you will have to go by photos and the seller's word regarding their condition. 

My non-posted G heads have had hardened-exhaust-valve seats and bronze valve builder liners installed, .013 taken off the decks, valve guides cut for viton positive seals, intake valves back-cut 30 degrees, and a three-angle (30, 45, 60) valve job. Cost for labor? $1200. Add the cost of Pac 1286 springs, Mummert's SI stainless valves, retainers, locks, and seals, and we're talking another $500-$600, excluding the cost of the heads. I ported the heads myself; if I had paid to have them ported, who knows how much more they would have cost. You must be concerned about cost; otherwise, you would not have asked. If money isn't a concerned, you could consider buying Mummert's aluminum heads, but I've heard that there's a two-year waiting list. 

Whether you buy G heads or Mummert's aluminum heads, you have to add the cost of rocker-arm assemblies, new or rebuilt.

This may help if not already posted - http://forums.y-blocksforever.com/Topic154841.aspx#bm154844

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Almost 20 years ago when I built the 340” stroker for my F code clone, Mummert suggested and provided a set of his ported 471’s. Got the compression down to 8.5. So don’t rule those out as useful heads if your going the supercharged route. Ran really nice.

miker
55 bird, 32 cabrio F code
Kent, WA
Tucson, AZ

Ted Eaton recently told me that he had built a normally-aspirated Y-block/w 471 heads and "popup" (domed) pistons that compensated for the larger combustion chambers. Ted said that it ran well. All 471 heads are posted and have hardened valve seats. Personally, I prefer smaller combustion chambers and flat-top pistons on normally-aspirated engines. 

If you want to use 471 heads, and are close enough to pick them up, I have a bare set that looks like they were professionally cleaned by a machine shop & probably checked. I'm not going to use them, and I would be willing to give them to someone who will, but not to anyone who intends to profit from them by selling them to someone else. I'm about 35 miles south of Sacramento. I will not ship them, even on your dime.  

That would be great but I live in Florida.  LOL!   I have never heard of a 471  head .  Can you tell me more about them?  Thanks, Ray

According to John Mummert's site, the 471 heads were used on Ford trucks that were equipped with the 292 and Mercurys that were equipped with a 312/w 2-barrel carburetor. They have the same intake valve and combustion chamber sizes as the 1957 F-code supercharged 312. You can find this information on ford-y-block.com.