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Drilling out a broken valve guide in an old 216 head with some rust ?

I've read posts here about removing valve guides by pressing (that is what the shop manual recommends) or by “tapping”. The concern is breaking the head casting. I haven't heard much about drilling out these guides. Is that safer than pressing or tapping/pounding, or does it create more problems?

The head is from a 1947 Chev sedan with a 216 cu in engine. It had valve work at a machine shop, but the engine “kept bending push rods”. It was removed, wrapped in a cotton cloth, and stored on top of the engine, with the hood closed - for about 40 years.... It was in surprisingly good condition - lots of surface rust but no deep corrosion. All valves were seized in the guides, but most were coaxed free with repeated penetrating oil and tapping over a week. These valves now move freely, and the valves and seats mate tightly. But two intake valves were severely rusted to the guide, and these two guides (cast iron) broke when removing the valves.
I'd like to take this head to our local (small town) machine shop to clean and assess for cracks, and if ok to replace the guides (should they replace them all ?), grind the seats, and install new valves.

Because the guides may be well rusted to the head, I'm concerned that pressing them out may break the casting. Is it reasonable to ask the shop to drill them out?

Would sure like to hear the wisdom of you who have the experience.
Thanks for any advice.

Jim

PS - the head is to go on my 1950 GMC 1/2 ton with a 216 engine, which is running great (compression 105-118 psi on all 6 cylinders), but has a cracked head leaking coolant. Temporarily repaired with JB weld.

Drill the guide out to within about 1/8" of the outside diameter, then use an air hammer to drive the remaining sleeve out. Machine a driver down to a few thousandths under the OD of the guide. Turn the air line pressure down to get a moderate amount of "thump" on the guide, not a massive pounding. I've had good luck with that method, especially after applying some gentle heat and soaking the drilled-out guides with a good dose of KROIL overnight before driving them out.
Jerry

The guides are .565" OD.

GMJim You might look to see if those guides have been knurled,that was a cheap fix for worn guides that in my humble opinion ruins them cause they'll wear right out. When the heads were young mechanics would beat the guides out with a big hammer,pound the new ones in !! Now that the heads are old,rusty,and fragile takes more care to change them. My last set I pounded out and pounded in new ones,ground them up and they are running,it is however possible to crack the head that way. To recognize the knurl look for a spiral groove clear thru the guide,also a little half moon notch in the top of the guide where they put their knurling tool in the guide. good luck you can fix it !! I've pressed em too seems like it is harder on the head than hammer method,never drilled any but on your 2 might be best rust and age are not friendly.

Just thinking out loud here, I wonder if you sink the head in a large pan of boiling water for about 15 or 20 minutes if that would expand things enough to hammer them out without damaging things???

Mike B

Not even close to hot enough, plus the guide and the head are both cast iron and expand at the same rate. The trick is to heat the head a little with a torch, after drilling out most of the guide to leave just a shell to be driven out. As always, a little experience and common sense goes a long way, and that's something that comes from making expensive mistakes, most of the time!
Jerry

Thanks for setting me straight Jerry! I figured there was a reason no one had mentioned it before...

Mike B

If boiling water could make guides loosen up in the head, they would fall out anytime the coolant got a little low!
Jerry

When I was a working man, we would remove shaft bushings from pump casings by heating it with a OA torch or rosebud, depending on the size. The idea was to get as much heat on the bearing as possible in the shortest amount of time, so you did not heat the surrounding area (in this case, the pump casing which was cast iron). The bushing would expand but the casing would not let it expand outward so it would expand inward. Once it cooled down to room temperature the OD of the bushing contracted enough to allow you to press or tap it out. In some cases, I literally removed it by hand.

As HotRod suggested, drilling it out so it is thinner will help that cause. The guide will heat up quicker thereby reducing the heat transfer into the head.

Edit: If you try this method, do not heat the head, only the guide.

Phil, on pump wear rings, we would just put a small weld bead on the rings, let them cool and they would almost always just lift right out.
Liquid nitrogen to install new ones and then machine the shaft rings to size.

It’s amazing what heat and cold can do to make things go on and off, or in and out.
Don

I used the same technique on pump wear rings. Heat, let cool then lift them out by hand in most cases. Liquid nitrogen to install.

One of the most challenging valve guide changes I've done was on an air cooled Porsche 914 with six individual cylinder heads tied together with two overhead camshaft carriers. The bronze guides were .008" bigger diameter than the holes in the aluminum heads they were supposed to fit. I made a special driver that would seat the guide at the proper depth in the head when it was driven home, and put the guide and the driver into a freezer overnight. Next morning, I'd heat the head with a torch and drive the guide in quickly. "Rinse and repeat!" It took 12 days to get all the guides installed! I was on my own with that one, as none of the machine shops around town would attempt the job!
Jerry

That’s strange, they must not have tried the dealership, my Porsche dealer says that company policy is to maintain staff, tools, equipment and documentation to service all vehicles ever built
Unlike GM, nothing is “too old”.
-s

The dealer's solution was a new engine. Wouldn't even talk about any repairs. “Edited by Moderator (comment deleted - political comment not permitted)”. Dealers in America might have had a different policy.
Jerry

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

As you've noticed by now, drill bits usually don't drill round holes, no matter how careful you try to be. I'd suggest going at the guide from the bottom side where it's not battered yet and using a piloted chucking reamer, not a drill bit, to cut the guide to within a few thousandths of the OD. Better idea- - - -spend a few bucks with a machine shop to have them set the head up in a Bridgeport mill so there's no wobble whatsoever and plunge cut the remainder of the guide out that way, possibly with a 4 flute end mill. At this point, continuing to use a drill press will probably guarantee a ruined cylinder head.

I sort of recall recommending an AIR hammer, not pounding on the guide with a regular hand held one. Here's an example of a driver for guides that fits an air chisel:

www.ebay.com/itm/284394251543?

I usually buy straight shank chisels and turn the pilot in the lathe to whatever diameter I need for the guide I'm driving.

Yes, a piloted guide driver is the only way to get one to move without chipping or otherwise damaging the old guide or the cylinder head. At this point, the prudent thing to do will be to bite the bullet and turn the job over to a machine shop with the equipment that might make it possible to save the head. They might have to ream the hole a little bit oversize and custom fit a guide to the hole with the proper press fit.

Well, I messed up using the hammer.
Did I understand the drilling correctly?
"Drill the guide out to within about 1/8" of the outside diameter, then use an air hammer to drive the remaining sleeve out. "
The OD of the guide is about 9/16 - so 1/8 less would be a 7/16 bit to drill out the guide
This leaves the remaining sleeve wall about 1/16 thick
Or did you mean leave the remaining sleeve wall about 1/8 thick

Sorry for the stupid question, but I'm trying to understand this

Thanks for your patience
Jim

No, you did things exactly right- - - -up to the point you decided to use a non-piloted driver, and a BFH. The air driver makes dozens of hammer blows per second, and once the guide starts moving, it slides out a little at a time. Getting that first little bit of movement without galling or cracking the head is the tricky part. When I was doing a lot of head reconditioning, I kept piloted drivers on hand for all the common valve stem sizes and the oversizes we usually drilled them out. The air hammer was also used to install the new guides, with a shoulder or a sleeve to assure the correct installation depth was accomplished. On the heads without removable guides like small block Chevy, we used multi-flute piloted drills to open up worn guides, followed by a chucking reamer to take out the last few thousandths and assure the right press fit for replacement guides. I used bronze guides on most of the racing heads instead of the cast iron ones we ran on street engines. Then the top of the guide was machined to assure the high lift cam wouldn't cause the spring retainer to hit the top of the guide, and it was usually machined for a positive oil seal that locked onto the top of the guide. We did a massive amount of work on heads- - - -and won a lot of races when our engines could breathe better than the competition.

Stovebolt heads have such convoluted passages and so many right angle turns for the mixture and exhaust gases to negotiate that doing fancy valve and port work is like putting lipstick on a pig! It's better to build a stovebolt engine for lots of low end and midrange torque, not high RPM.
Jerry

ok - to complete the story of "what I should have done":
On a metal lathe, cut down a straight shank air hammer chisel to be just a hair less than 7/16 for the pilot with 9/16 for the business end of the driver.
The common air hammer I see advertised has a .401" round shank https://www.mcmaster.com/air-hammer-chisels/
but it looks like shaft on the chisel is only about 1/2" and would be too small

from the previous link you supplied for an example of an air hammer guide driver, they recommend a heavy duty air hammer
"We recommend you use a fairly powerful air hammer to drive this tool, some of the cheaper or lighter weight air hammers have problem with stuck guides."

Do you have a recommendation for an air hammer that will do the job ?
Where do you get your air hammer chisels ?

McMaster Carr offers at least 3 sizes of air hammers. Link They rate them by piston stroke, with longer stroke being more powerful.

I simply make a sleeve out of drill rod to fit over the air hammer chisel shank and turn the end of the chisel down to fit whatever hole it needs to pilot in. Sometimes a couple of different pilots will work on the same shank- - - -maybe 5/16" and 3/8", for instance. Stovebolt and Chevy V8 valve stems are 11/32" (.343") so I always kept dedicated tooling around for that size. Once the driver sleeve is made on the lathe, I harden it- - - -in either air or oil, depending on the base material. I always used whatever air hammer the Snap-On tool truck had onboard, with a good warranty, but I was doing enough business volume to justify buying professional-grade tools.
Jerry

Very clever - that is a bit of machining, but ends up with the exact sizes needed.
If I follow correctly, the machined sleeve will have an ID of 7/16 (to match the pilot) and an OD of 9/16
So the wall will be fairly thin about 1/16 inch - same as the remaining bit of valve guide left in the head.
Am I on track here ?

Back to the air hammer
As Kevin just said, McMaster lists three air chisel hammers - all with the common .401 " straight shank attachment
low power has a 1 5/8" dia cylinder and beats the fastest at 0-5000 beats per minute
medium power has a 2 5/8" cylinder and beats a bit slower at 0-3500
high power has a 3 1/2" cylinder and beats slowest at 0-2000

If I was doing this properly (before the BFH disaster) would you suggest the highest power ?

Snap-On lists medium and high power air hammers with similar dimensions

I believe the medium one will have plenty of power, especially if you have a good source of compressed air. I'd suggest around 100 PSI, minimum and enough volume to keep the pressure from dropping quickly as the reservoir gets drained. Be sure to leave a bit of clearance on the OD of the driver to avoid scarring up the cylinder head holes. 20 thousandths or so should be plenty. Have fun!

All the above can be done with a single driver shank, and a series of custom-fit tips that slip over the end of the basic driving tool. For instance:

www.ebay.com/itm/284394251543?

Jerry

Got it now, thanks for all this Jerry,
Just for interest, the OD of the valve guide is .565
What would be the ID of the hole in the head casting - how tight of a fit is it ?

Just a WAG, but we usually tried for a .0015-.002" press fit on the guides we installed. Bronze guides get a little more of a press than cast iron. Once the new guide is installed, it gets reamed for the proper running fit for the valve. Heating the head and/or freezing the guide makes for a smoother installation, as it shrinks the guide and expands the hole in the head a little. Make sure to have some kind of positive stop in place to assure all the guides you install end up at a uniform depth, as it's easy to drive one too deep during the installation process. I used a flat washer on top of the guide and a stop sleeve around the new guide for for the washer to butt against.
Jerry

That all makes sense.
One last question on the technique of drilling out the valve guide and then using the air hammer to drive out the shell.
Did you find that drilling made a big difference compared to just using the air hammer and appropriate piloted driver.

If this rusted head was in your shop and you wanted to replace all the guides, would you try each one first to see if it would move before drilling it ?

Actually, I'd use my valve seat and guide machine with the air float table to position the guide precisely under the spindle, and bore the guides out to a thin sleeve, then ream the remaining material out. I have an assortment of chucking reamers in .001" increments that can cut guides away without enlarging the bores in the head. That machine minimizes the error when installing new guides and also makes it much simpler to machine the valve seats to align with the new guides. Sometimes when the guides are installed with hand tools, it takes quite a bit of seat grinding to align the seat with the new guide. That machine and the associated tooling sold for about $15K when it was new, but I was able to purchase one used for about $2K. Ditto for my crankshaft grinder- - - -I bought two of them for $3K, a running machine and a disassembled one for parts, for a total investment of $3K. The same one in "as new" condition usually sells for $20K or more.

To answer your question about trying to make the guides move before drilling- - - -it doesn't hurt to try, but it's a crapshoot about whether or not they will move. Just don't try to force things.
Jerry

You make a pretty convincing argument to do this right in the first place.
The effect of valve guide mis-alignment on the valve seat fit seems really significant.

Can we back up to the (maybe not so good) idea of using a piloted chucking reamer to try to salvage what I have.
In my dreams, if the old guide can be reamed down to a thin shell, eventually would the thinnest portion crack away from the head casting, and then the entire shell could be removed in pieces.
Does this ever happen?
Or is the old guide somehow rusted tight and needs to be machined out.

Here's a sneaky trick that might save you a bit of effort and frustration- - - - - -grind the back of a fine-toothed hacksaw blade down until it's narrow enough to fit into the guide you've drilled out, and carefully cut a slot or two almost all the way to the edge of the guide. Then make a piloted driver and give it a good whack with that BFH. Chances are that by weakening the shell of the guide by slotting it you'll be able to make it move without going to extremes making more tooling. Just be careful not to cut into the head casting while you're slotting the guide.
Jerry

Those of us with CNC equipment need nothing more than 1 cutting tool and some needle nose pliers to remove bolts, studs, bushings, guides, etc.

I just priced out a 9/16" HSS chucking reamer at $42.90 from MSC... If one were to buy these in .001" increments from 1/2" to 5/8" it would cost more than $5000.

Phak 1 In 72 when I ran the machine shop in the parts store we got a lot of axle bearing changes. Would take the hot OA torch,heat the lock ring in one spot knock it off with a chisel,press off the bearing ,press on the new one,press on new lock ring. Usually not discolor the axle. Hard to press those off together axle will bow and become explosive..

Excellent!
Just be careful.

Hacksaw blade to CNC machine - that is quite the range in technology. . . .

I was thinking of a hacksaw blade but I was afraid to even ask the question
What is the main fallout if the blade does cut into the head casting ?
Is it mis-alignment of the new valve guide to the old valve seat - or is there something else

A slot between the valve guide and the head might result in a vacuum leak or an exhaust leak, depending on which guide it is. If the head gets grooved, ream the hole out a few thousandths to smooth it up and use an oversized guide fitted to the hole for the correct press fit. Apparently, our high tech guys have never heard of an adjustable reamer, or anything else that requires a little common sense. They can brag about how much their equipment costs, however.
Jerry

Gentlemen, please play nice to each other. We are trying to help the OP!

GMJim, at this point, the cheapest and surest way to guarantee success would be to bring it to an auto machine shop. They handle replacing guides on a routine basis.

If I had to stoop to the level of others here and do this manually I would use a piloted counterbore tool similar to the attached picture.
McMaster-Carr offers these tools in an interchangeable pilot style including 11/32"

Cutters:

https://www.mcmaster.com/counterbores/high-speed-steel-changeable-pilot-counterbores

Pilots:

https://www.mcmaster.com/counterbores/steel-pilots-for-changeable-pilot-counterbores

If one has a lathe handy an old valve stem could be easily made into an extended length pilot.

Stoop to the level? Gimme a break.

There's more than one way to skin this cat. No need to pooh-pooh any idea.

OP here - thanks everyone for offering your ideas.
I get that we all have different life experiences, and different opinions, and different ideas.
What I love about this forum is that people are willing to share what they have learned.
There will be different ideas - and conflicting ideas - but for a newbie like me, I like to gather all the different opinions, and then make up my mind of what to do.
I've done more work on this old truck in this last year than I have for the previous 20 - thanks to all of you.
This forum is great - I support it with donations - keep it going.

So - back to my original question
I've got an old moderately rusted head as a possible replacement for the cracked head in my truck.
- the valves were rusted solid in the guides - I broke two guides getting the valves out.
Maybe this head is not worth trying to save - here is a photo before I started trying to clean it up.
I read somewhere - maybe not on this forum - that if a shop is not experienced in working with old cast iron heads, they will press the guides out and crack the head.

Is that a real concern, or is that one of those modern myths.
Has anyone actually had a head ruined by a well meaning, but inexperienced shop ?

Jim

Cast iron is funny stuff- - - - -push on it and it breaks- - - - -hammer on it and it bends. That's how a cast iron crankshaft is straightened after it's had a journal welded. Suspend the shaft on V blocks, find the high spot, and thump it with a lead hammer. Press on it and it will crack or even break. The accepted way of removing and installing valve guides has been with an air chisel and the proper size driver for as long as I've been doing engine machining- - - -a bit over 60 years. I'd much rather salvage an unbroken valve guide by installing a bronze sleeve and reaming the sleeve to fit than stressing the head by trying to replace the guides. The guide liners and reamers to install them are on Ebay for a lot less than a machine shop will charge you, especially one that has a bunch of new equipment to pay for.
Jerry