Anyone who has dabbled at head porting will tell you that one of the most likely
places that a breakthrough will occur is at the pushrod holes. In most cases, the intake port will
have restricting bulges in the side walls to allow the passage of the push rods on
either side of the port. These bulges are also usually the first thing porters attack
when porting a head. Some break through these bulges, requiring a sleeve to be installed
to reseal the push rod hole. I am going to break through on purpose so that I can
install a sleeve to achieve maximum width at the flange and maximum radius of the wall on an intake port.
Sleeving your push rod holes may not be practical, safe or suitable for your
head, engine or application. You should also make sure your push rods
will fit inside the sleeves without interference. If you do this, do so at your own risk.
What I want to do is to increase the radius on the inside radius wall of an intake
port. But by doing this, I run the risk of breaking through the push rod
hole on that side. So, by going ahead and breaking through, then sleeving it,
I am able to obtain the greatest radius on that wall and not have to
worry about the push rod hole.
The first thing I do is break through the push rod hole using
a large stone. I use a large stone so that I won't go tearing
into the push rod hole when I break through, as might happen
with a small carbide burr. The breakthrough is indicated by the
pointer. Now I know where the push rod hole is.
Next, I cut the wall down close to the push rod hole with
the flat side of this tappered burr. If you look closely,
you can see that the metel turns dark when it gets real thin
as I get close to the hole.
This is brass tubing that you can buy from any hobby shop,
and some hardware stores now carry it. The 4 sizes shown
here are 9/16", 19/32", 5/8" and 21/32". You can see that
it all fits within each other very snug and is great for
building custom bushings, spacers and bearings. But I digress.
It works well for sleeving your push rod holes too. It comes
in 12" lengths and will cost you a couple bucks per at this size.
The tubing is easy to cut by deeply scoring with the edge of a
file all the way around, then snapping off the piece. Just cut
your piece a little longer than needed and don't worry about
the ends. You can trim them after installation.
Before appling glue and inserting into the push rod
hole, fill the leading end with plumbers putty to
keep the glue out of the tube as you insert it. A
small container like this is about a buck and is
great for making intake clay radiuses and filling
ports and pockets and spark plug holes when air flow
testing ports. It is oil based so you can leave it on
your heads for quite a while and it won't rust them.
I don't know if it will affect aluminum adversly if
left on for too long.
I found this 19/32" tubing fit my E7TE head well enough
to glue without drilling the push rod hole bigger. It
had a little clearance but the epoxy will fill the voids
well. After cleaning the push rod hole with laquer thinner
and sanding the outside of the tubing, I applied epoxy
to both the hole and the tubing and inserted the tubing
with the clay filled end leading.
When the glue set, I finished shaping the port wall and sanded
the breakthrough smooth with a sanding roll. Look how straight
I got this inside radius wall! I was able to open it from 1.010"
to 1.080" wide.
Using a small stone on a Dremel, the tube ends are trimmed flush with the head surfaces to finish the sleeve install.
More good stuff!