Update - well . . . . . not quite as expected
I sure wish you folks lived next door so I could have your eyeballs and fingers on this head.
Thanks everyone for your help.
Some questions:
Panic - yes the OD of the guides measures .565 - does anyone know what the dia of the hole is?
It is meant to be a tight press fit - any idea how tight?
9/16” works out to .5625” - which would be about a 1 thou pinch on each side
Does that sound about right ?
Jerry - sounded like a grand plan, but wish you were here to coach me
Photos attached of the broken guide before and after it was cut square.
The ID of the guide is .343” - just a hair less than 11/32
I used a set of drill bits starting at 11/32 and stepping up by 1/64 until I got to 7/16
They drilled pretty easy by only taking that tiny cut each time.
So then the ID of the shell was about 1/8” less than the OD of the guide - leaving about 1/16” thickness - too thin?
I made a driver from the shaft of a hardened 9/16” bolt - (cut off the threads)
Soaked the guide in several different penetrating oils for a week - including acetone & ATF
(no KROil available here)
Then being impatient, I used the driver with a big hammer to tap tap tap, then a bit more of a tap.
The shell just mushroomed like pounding a rivet - didn't budge at all.
When you machine your driver, do you make a shaft that would slide inside the valve guide and then make a step up to the OD of the guide. Would this have made the impact more vertical down the guide, and less likely to mushroom ?
Please don't shoot me - I'm still trying to learn from all of this.
fixite7 - the guides don't look like they have been knurled - thanks for that tip.
I tapped the mushroomed portion with a flat punch and broke off the mushroomed part.
A small part of the shell chipped off as well, and I hoped the rest would also chip out, but not to be.
It is still really solidly attached.
(third photo)
Hoping now to just drill it so thin that the shell would break, I worked it up to 15/32, but the shell is still strong & doesn't want to beak off
Last photo is from the bottom looking up - the drilled hole is oval as I made a mistake with the initial angle on the drill press.
At this late stage, I then got my neighbor (retired welder) to heat just the shell with his oxy-acetylene torch and then let it cool. Did this 3 times. 25F outside, so it cooled pretty quickly. No change.
Then heated the whole head up with electic heaters and propane torch to smoking hot (120C on the infrared thermometer) and sprayed a canned auto cooling spray into the shell hole. Man it cracked and popped like the whole head had cracked, but nothing had changed.
I think I can drill up to 1/2” and still not touch the side of the head casting.
If the hole in the head is 9/16” that would leave 1/32 for the shell wall thickness.
Has anyone actually done this - completely drill the guide to a thin shell that can be removed or broken in pieces ?
Any suggestions ?
Jim
