In this chapter of the never ending saga of the unhappy Hemi, I have discovered some cracked valve guide bosses. On #6 intake, I screwed up the spring seat when I was using a comp cams seat cutter with a hand drill. 15 of them went perfect, but this one got cocked somehow and cut crooked. So I put it in the mill like I should have done in the first place and cut it deeper to straighten it out, but it broke thru into the intake port. So I had the seat welded up and re-cut it to the perfect depth using the Bridgeport. When I went to grind the weld drooble out of the port, I saw the cracked guide boss. Carb cleaner sprayed into the spring seat leaks into the port.
So I looked at the others and there is a few smaller cracks that don't leak when tested with carb cleaner. I've never had this before, so I'm not sure if I can just seal it up with some epoxy, or if this is a catastrophe waiting to happen and I need to remove the guide(s) and get it/them welded up. This motor is to much $$ to just throw it together and see how long it hangs together if this is a big risk. I need to know if it's completely safe to run, or not. If I have to do the big repair, the seats will have to be recut after the guides are reinstalled, and no one is going to do all that in a week so I will for sure miss the Midwest drags and lose my $500 entry fee. Does anyone have experience with this type of crack? What did you do, how did it work out? THanks, JOel

Well, here's an idea, Install a valve without spring, build plate to cover port w/ vacuum nipple. Pull vacuum in port and fill cracks with thin, hardening epoxy or sealant of some kind dripped onto top side. Clean up prior to hardening. Which sealant or epoxy? I don't know, but I bet someone has a suggestion.

I hate to say this, but I want to give you my experience. First aluminum is not as strong as cast iron, that is why most aluminum engine parts are a lot thicker, to make up for the lack of strength. A cylinder head originally designed in iron and then made out of aluminum, has a hard time finding places to increase thickness to make it strong enough. If you have cut the heads thin enough that you are seeing air, even with welding, and or epoxy repair, how well will these heads hold up under the stress of an operating engine? I have seen ported aluminum heads so thin that the valve seats warped when you torqued them down. Just because you can come up with a repair that stops leaks, does not mean that repair will make the head useable. As expensive as a Hemi engine is, why throw good money after bad? I had a buddy lose a couple engines from a set of old hemi heads that had been patched so many times, he now has a new set and no more engine problems. The other issue with aluminum is what they call a fatigue cycle. That is why aluminum rods have to be replaced on a run cycle. Ferrous metals have a long stable fatigue cycle, aluminum does not. The best way to describe a fatigue cycle is take a piece of wire and bend it back and forth until it breaks, the number of bends, is the fatigue cycle. Old aluminum heads like to spit out valve seats, it is my take that the fatigue cycle of the metal holding the seat, loses the interference fit to keep them in place.

Looks like just another day in my W5 past....

My .02 is......
Don’t mess with any that aren’t leaking thru.

If it’s only the one that’s leaking...... “what I would do” is mark the top of the guide so it can be reinstalled in the same orientation to the hole.
Push it out, clean the guide and hole thoroughly with carb cleaner, reinstall guide with the guide and hole coated with green loctite.
Let sit overnight.
Use black “right stuff” around guide top and smear some in the hole of the spring cup.
Install a valve and spring into position while the right stuff cures.

The seat should be touched up with a stone to insure concentricity to the reinstalled guide.

Thanks for the replies so far. These heads aren't old. I bought them new in 2014, but they only have 45 passes, and about 1500 street miles on them.

Call my engine builder Ron Farley...I am sure he has dealt with this in the past.....716-799-5588. He has seen and fixed it all on these engines. Me, I would order a new set of heads while these get fixed if that's possible.

This is an early Hemi, stuff for it takes forever to get. Especially now.


I finally got a hold of the guy who did the heads for me initially. He said he sees this a lot with these heads.. He said at the time that Hot heads built these heads, they had too tight of a press fit for the valve guides. The problem has since been resolved in their manufacturing. He thinks because the crack goes up and down, it is unlikely that a chunk will ever fall off and be ingested into the motor, and since the valve guide has a flange on top, and being too tight to begin with, it's not going anywhere. So he recommends putting some right stuff in the spring seat around the valve guide, press the shim into it and assemble the valve and spring before the right stuff sets up. Sounds like an easy enough solution to me, but I'd still have the fear of a ticking time bomb rolling around in the back of my head.

That is going to be one of those drag week phantom noises you hear on the road. "Jeff did you hear that?? sounded like a piece of aluminum falling off off a valve guide!"

I’ve seen many heads with cracks like that.
The crack itself wouldn’t bother me at all.

My suggestion for the green loctite was simply to aid in plugging the oil leak.

Fast, I appreciate that very much and it sounds like a good idea. But he said since these guides are installed too tight, don't try to get it out.

I've had some pretty knowledgeable head guys tell me not to worry about small cracks around the port side of the guide.
Doug

We have lots of OEM early Hemi heads down at the shop.....And yes, even an aluminum set from Hot Heads...