Try this link for how to spot posted heads.

Identifying posted heads

Lorena, Texas (South of Waco)

While detonation is a key player in the head gasket failure in un-posted heads, the actual head deck thickness is still the major consideration.  The un-posted G heads simply have thin deck surfaces as delivered from the factory and as a result there is a balance point between the compression ratio and amount of head mill before gasket failures will be prevalent.   A less amount of head mill and more compression or more head mill and less compression is the balancing act that must be played with the un-posted G heads.  But ultimately there is a point of no return where excessively milled heads simply do not have enough internal support in which to hold the head gasket firm regardless of the compression ratio.  So with that taking place, retarding the camshaft would not help.  The Ford manual is pretty specific in limiting milling of the ’57 heads to a maximum of 0.010”.  Once the heads became posted, the rules changed and more aggressive milling or increases in compression ratio could take place with less chance of head gasket failures.

 

Un-posted G heads can have posts added to cylinders 1, 3, 6, & 8 which will give these particular heads another shot at being used successfully with higher combustion pressures or save a set of heads that have already been milled.

Lorena, Texas (South of Waco)

Ted,

Would it be safe to assume that, exact static CR #s notwithstanding, if it runs ok on pump gas without having to retard the ignition, a properly prepared/assembled motor with good unposted "G" heads should not (under ordinary circumstances) suffer gasket failure?

If presented with an engine who's static CR WAS borderline, wouldn't the simplest cure (as opposed to tearing it down and starting over) be merely to retard the cam timing a bit and lower the dynamic CR? You would then have the additional "easy" adjunct of retarding/fine-tuning the distributor a tad if absolutely necessary?

6 VOLTS/POS. GRD. NW INDIANA

Thank you Ted, I have printed out the instructions for posting, but I just don't have the tools to do it. I am taking the heads and block (which can't keep a rear main in it) to my builder to see what he can come up with. I have some old C heads, but I have recently found some 471 heads which I think I will use.

Jan  Urbanczyk  Major USMC Ret.

                                                                 Bowie Maryland

Most domed pistons have a 10cc dome so I used that value in the following calculation.  A +030 over 312 with the pistons 0.025” in the hole and heads that have only a light cut (68cc) will still net 10.0:1 static compression ratio.  This will prove to be too much cr for unposted G heads even if they are not milled beyond 0.025”.  If the block is zero decked or is bored larger, the cr simply gets higher and compounds the issue.

Lorena, Texas (South of Waco)

It’s the unposted ECZ-G heads that appear to have the most issues with blowing head gaskets either when the compression ratio is stepped up or the heads themselves have been milled more than 0.025”. The ECZ-C heads are cast differently in the water jackets around the intake ports and because of this they do not have the same propensity for blowing head gaskets on cylinders 1, 3, 6, & 8 like the ‘G’ heads do. Here are a couple of links to past threads on do it yourself posting of the G heads.

http://forums.y-blocksforever.com/Topic33877-3-1.aspx#bm33879

http://forums.y-blocksforever.com/Topic47592-3-1.aspx

Lorena, Texas (South of Waco)

Doug, Bill is the man that built this engine, using, if I remember right, the rods I got from you. I am taking the whole thing back to him today or tomorrow and I really hope that he can figure out what is wrong.

Jan  Urbanczyk  Major USMC Ret.

                                                                 Bowie Maryland

Jan,



Try to get a handle on Bill Coleman who was a co owner of Coleman Bros Speed shop on Rt 1 in Bowie Md. He retired, sold his interest in the speed shop, and moved all his machines and tools to his home near BWI when Rt 1 started to be redeveloped. If the speed shop still exists they might have a contact number. I do not have a number any more but he did all the machine work on the last Y block I built in 2007. He is very knowledgable about the Y.



He will know how to measure the amount milled off the heads but it is actually pretty easy to do. Just measure the thickness of machining pads below the exhaust ports on the heads. They all came from the factory at exactly 1". If your heads measure in at 0.950" then they have been milled 0.050". Most people in the '60's would mill 0.060" off them without problem using flat top pistons.

Doug T

The Highlands, Louisville, Ky.

Check John Mummert's Y Block site for a complete list and description of heads.

Jan  Urbanczyk  Major USMC Ret.

                                                                 Bowie Maryland

If one was shopping for factory posted heads what would one look for?

Doing Fords for 45 years. '56 Customline Victoria

E.J. in Havana FL