I've been looking over some G heads, got a few sets of ported heads, they look good, but i was wondering before I started playing with set myself. was thinking about thin sleeving the pushrod holes, so I could get right on the dog legs, I remember reading about it a long time ago. seems very workable, would like some feedback.

Po ol Davie

Sparta , Tn.

What you’re proposing has been done and is a good idea.  Just be sure to use thin wall tubing and consider using 5/16” pushrods to insure adequate pushrod clearance.  The other option is to install the sleeves after breaking through to minimize grinding on the sleeves.  Seen it done both ways.

Lorena, Texas (South of Waco)

Thanks Ted for reaffirmation from you, I was also thinking offset drilling one drill size or two larger away from said grinding area to insure push rod clearance. 

Po ol Davie

Sparta , Tn.

Ok, so quick couple of question, as I have often considered this approach:

What do you do to secure the sleve in the head, both to prevent movement, & vaccume leaks? 

Has anyone ever done flow bench #'s on this vs a strip, or street port? 

Is the head bolt bend a worse culprit in the flow charactaristics than the pushrod bend?

I would think , a small 45 deg. chamfer on both sides of the head, close to a press fit for sleeve, a tick of a flare, should do the trick.

Po ol Davie

Sparta , Tn.

Also include using some sealer on the sleeve.  Loctite would suffice for this. 

The bend around the head bolt is another story.  Not unusual for the area around the head bolt to be broken into and especially if redrilling the heads for ½" head bolts.  Not a problem though as the head bolt seals this.

Lorena, Texas (South of Waco)

So has there ever been flow tests done on sleeved heads?

How benificial on street, or cams under .500@valve?

That sounds like a John Mummert question as he is the flow expert on the Y heads.  I would suspect it depends to some degree if the sleeve is put in as a repair as a result of grinding too far to begin with or if using the installed sleeve as a guide in knowing where to stop.  The repair could potentially be a protrusion into the airstream while the sleeve being using as a stop point for grinding would permit a smoother air flow.

Lorena, Texas (South of Waco)

Mongo: I'm hardly an expert on Head prep but it's generally acknowledged that John Mummer is. I've read his articles carefully that were published in YBM around 1998. First, the biggest impedence to good head flow on Y-Blocks is the original intake manifolds. None will support properly ported heads. (Neither will the old Tri power setups, particularly the Offy, which is a performance dog.)   However, this was prior to the issue of the Blue Thunder intake. As for sleeving the heads, according to him, unless you are building a full out race engine it probably isn't worth the effort, unless you have broken thru. Proper prep, which appears to be a challenge to get right, will largely get you by the pushrod & head bolt problems, according to Mummert. Apparently just chewing material out of the heads to make things bigger isn't the answer to good flow.         

Paul