And hopefully I don't get my hand smacked for this, but one of the heads has a crack in the exhaust valve guide [EDIT: in the head itself at the guide], so I'm considering replacing both heads with a set from an '83 while I'm at it. Apparently new members can't post in the WTB, so if you're holding I'd like to talk to you.

 

No, boring does not affect the head gasket on these engines. The cylinder has a protruding ring above the gasket face that indexes into the bore of the head. The ID of the head gasket matches this ring. If heads are surfaced due to being warped or to increase compression, the height of this ring must be checked and possibly adjusted, but it still doesn't affect the gasket. On to the crack in the valve guide. As long as it's just the guide that is cracked, have the heads rebuilt and all guides checked and replaced if needed. Guides are items that are easily and often replaced, so no big deal. I wouldn't put a set off another engine on without rebuilding them anyway.

 

No, boring does not affect the head gasket on these engines. The cylinder has a protruding ring above the gasket face that indexes into the bore of the head. The ID of the head gasket matches this ring

That's what I thought, but glad to get confirmation.

As long as it's just the guide that is cracked

It's not, it's a crack in the head itself where somebody pushed in a guide crooked. A couple of people have told me that trying to weld it would be more trouble (and risk) than it's worth.

 

You got pictures?

 

It's small, but it's there. It doesn't go all the way through, but the more I think about it the less comfortable I am running it like this:

 

If that were my head, I'd knock the guide out and look closely to see how deep that crack actually is. That area of the head is pretty thin, and if the crack doesn't go very deep I'd cut down to the bottom and weld it, then machine it back. That's only because I can do all that myself in my own garage. If I had to pay someone else for work, I'd find a better casting and have it rebuilt.

 

/\ ditto. If it a shallow crack and you have a or are a good dirty casting welder, fix it. Cast dirty auminum can be a can of worms. Check welding tips and tricks on youtube on dirty cast aluminum welding. I usually heat and not start a puddle 3 or 4 times to bring the pepper, out cleaning off the pepper each time. Then just do small beads. You will still be fighting pepper just stop and clean and repeat.

 

(Question from the Peanut Gallery: Does pepper = embedded foreign matter? If not, then what please?)

 

Pepper is contamination in the aluminum. When welding it comes to the surface of the weld and looks like pepper. Cast dirty used aluminum is the worst.

 

Watch starting at 5 minutes.

 

I actually would really like to try my hand at fixing it, but I'm not set up to do it. I'll probably hold on to it and see what I can do with it when I get some of my other projects out of the way.

 

Let me add even new clean aluminum needs to be cleaned of the aluminum oxide layer that builds up and has a higher melt temp than the aluminum and will also cause pepper. That occurs when you have a weld started on clean prepped and you get your puddle on to unprepped metal which can cause the oxide to float in the pool.

 

affermative Joe @Ratso ,AC breaks the oxide layer whilst welding , DC can’t be used for that reason, in cast iron and aluminum i usually drill a tiny hole at the end of the crack to break the tension (or the assumed end).
Scrape clean the material with an hss blade to start with and wipe it with aceton , still the contamination remains the surprise act.

 

Thanks, and thanks for the swell video. Love that stuff.