can anyone tell me the difference between the posted and unposted G heads? How do you tell them apart, and what the pro's or con's, if any, between them? Thanks in advance



Buz

Buz Mills

Dallas, TX

E-mail ted . He is one of the administrators . He can fill you in.

55Birdman  Hickory NC

Thanks

Buz Mills

Dallas, TX

Posted heads have a post cast above the combustion chamber, in the water jacket.  I think it's over the flat part of the chamber.  It can be felt with a finger through the water holes.  It adds additional suppport in that area.  for a naturally aspirated street engine it should not be of much concern.  However, posted heads should be used for boosted or high compression na engines.  late '57 and newer heads are posted.


Lawrenceville, GA

Here’s a link to previous discussion including pictures regarding posted head identification. 

Identifying posted heads

Using the search function on this site will bring up other discussions regarding posted heads.

Lorena, Texas (South of Waco)

Hi Drof,

You really didn't give much info as to why you are interested in posted vs non posted heads.  For stock ECZ G heads, the shape of the combustion chamber and ports is the same for posted or non posted heads. So for more or less stock performance, non posted heads are just as good posted.  But if you are building a high performance engine especially one with high combustion pressures (that is to say High Compression or supercharged applications) then posted heads are prefered. Also with Y's, especially smaller displacements of say 300CID or less, and flat top pistons, it is difficult to build much compression without radical head milling. The posted heads are very applicable in this case because when the head surface is thinned down a large amount (say over .050") the head gets weak and head gasket leaks start to happen. But posted heads are less likely to be weak when milled a large amount. 

Doug T

The Highlands, Louisville, Ky.

Just an added thought. In the olden times guys "posted" their own non posted heads by drilling down from the top of the heag tapping for threads and putting a threaded rod down to support the combustion chamber from the inside. It is cheap and it might even work. Why pay big bucks for this?