Bill thanks for the info, it looks like only .010 inch has been removed so that is a good thing.

  Vic Correnti

Vic, thanks for bringing up very interesting post and the information from that is very informative!. I believe as a guide if you measure the small square shaped tabs on edge of head below spark plug holes, that originally should measure 1" or .1000 ", any less is amount removed. best regards bill.

  AussieBill            YYYY    Forever Y Block     YYYY

 Down Under, Australia

Ted, my heads are non posted 'G' stock size valve ported heads. How can I tell how much they have been milled? I am looking to have another .009 milled to make them flat and add the posts. I am itching either to patch these and wait for the aluminum heads or invest in a set of posted bigger valve ported heads. I am itching to go fast and it is getting cold around here in northern Illinois.

  Vic Correnti

Vic.  For the ½” head bolts on the Y, I’m torquing the short bolts to 100 lbs and the long bolts to 105 lbs.  Have experimented with up to 130 lbs but found that much bolt torque was not needed.

 

Are your heads posted or unposted?  I’ve seen head gasket sealing problems with unposted 'G' heads that had any serious milling performed to them in performance applications.  My rule of thumb for unposted 'G' heads is a maximum of 0.025” but I see where the Ford shop manual wants to limit the amount to 0.010”.

 

I have a pair of well used small letter 'G' heads that have been posted by going through the 2nd from the left rocker arm pedestal and cutting the bolt off flush with the pedestal mount.  Posting the heads this way reinforces both cylinder #3 and cylinder #6.  While this particular pair of heads were on a dominant circle track engine back in the Sixties, they were also heavily milled after the ‘posts’ were installed and held up fine with popup pistons.  I’ll try to clean up the heads this week and get an ideal exactly how much they were milled and post that information.

Lorena, Texas (South of Waco)

Vic, the problem only occurs on the cylinders fed by the upper ports. For some reason #1 and #8 don't seem to have the trouble. On the lower port cylinders the port wall stiffens the head.

There is 3/4-1" of material in the rocker bosses so there is plenty of room to thread the top. Spot face the roof of the chamber as JohnF suggests so the end of the bolt has a clean surface to push against.

All of this is done with the head sitting on a flat surface, drilling straight down. I have only done this to 2 sets of heads. Both sets were for street use but 1 set was S/C'ed and made 520hp. Haven't heard of any problems

http://ford-y-block.com 

20 miles east of San Diego, 20 miles north of Mexico

Vic:

I torque the top row to 85, the bottom row to 80, thinking the top row needs a little extra because each bolt has to cover a lot more area than the bottom.  I use grade 8 bolts.  My heads are factory posted, so I don't do the added posts anymore.  3 and 6 are the only cylinders I had trouble with.  If you have problems with #3, you should also have problems with #6, since the head fits either side.  I wonder if there is a detonation or mixture problem with #3.  I have had several people tell me I should O ring it, but as we know, it is not feasible to O ring the block with the shape of the combustion chamber.  But with modern machining centers, it shouldn't be too hard to O ring the head.  Problem here is that the groove, no matter how small, weakens the already weak head surface somewhat.

John - "The Hoosier Hurricane"

John, what are you torquing the 1/2 inch bolts to. I added studs and have been torquing to 100 foot pounds but still have the problem but the pressures with the nitrous are something that I don't know and my total advance is 32 degrees. I also don't know how much these heads have been milled. Is this a problem for all of the cylinders? So far I have only seen it on number three but was wondering if I should add the post to other cylinders.

  Vic Correnti

Vic:

I have done as you have suggested, drill and tap through the head surface just outside the fire ring, screwed a piece of 3/8 allthread against the "roof" of the head, and cut and ground the allthread flush with the head surface.  Lock Tited the threads.

I have also drilled as John did, (but not the same head)but drilled the hole 1/2" and used a replacement valve guide with a 3/8 hole for a sleeve.  I drilled through the head surface, drilled and tapped the block for a 3/8-16 bolt, spot faced the inside of the deck surface for the guide to seat against, cut the guide at the top so that a 3/8 socket head capscrew would not project above the rocker stand boss, put rtv on the end of the guide and around the guide at the top to seal any water.  I now had an extra 3/8 head bolt, right in the weak area.  I later changed to 1/2" grade 8 head bolts, made sure I don't exceed 30 degrees total advance, and seem to have ended my blown head gasket woes and no longer use the extra head bolt. 

John - "The Hoosier Hurricane"

John, thanks for the reply I have an issue with blowing the head gasket near the top coolant port left of center looking at the number three bore. I think I found the nitrous limit for this set of heads but I need to do something until the Aluminum heads are available. Did you do each bore when you did this and what kind of application (race or street) were the heads used for? Approximately how much stock is there from the rocker stand surface to the coolant opening?

  Vic Correnti

Drill straight down and tap to the size bolt you're using.

http://ford-y-block.com 

20 miles east of San Diego, 20 miles north of Mexico