thank you, this is the info I’ve been looking for from somebody who’s done it.

 

Trying to feed off this discussion because I just did the exact same thing trying to fix my plenum gasket issue. Ive also discovered several other leaks on the engine and bought my truck to build up a bit so I'm wondering if it's worth replacing the heads as well. I've heard they're notorious for cracking behind the valve seats. Is this true and would it be worth just spending the 500 or so to get oem similar replacements? I'm thinking of throwing a slightly more aggressive cam from hughes in while I'm at it.

 

I still haven’t fixed mine. I live in the middle of nowhere so I’ve been using my old Yamaha WR450F to get around until I can figure out the best option I can afford. I tried to drill them out but my bit broke inside of one of them so now idk what to do. I’d like to just get a good used motor but I don’t have $500 just sitting around and another $100 for a cherry picker.

 

Clearwater/Odessa cylinder head made stock replacement heads, with thicker decks, so, they are not as prone to cracking.... Not so long ago, they were reasonably priced, today? No idea.

 

The heads Hey You recommended look to be about 850 now. Jegs has some with built up valve seats for about 450 but might be a get what you pay for scenario. My hesitation with getting a junk yard motor is running into the plenum gasket issue, going to fix it and breaking the bolts off again and being back to square one. I'm two for two on these motors having this gasket issue.

 

What size bit was it? I get it stuff happens. Work slowly, Pull the drill out periodically to clear the chips and make sure it is OILED! Try a carbide tipped drill bit, If the bit that broke is small you can drill smaller holes around it and get it out. Worse case you will have use a helicoil. I broke a bit off trying to drill a pilot hole in a 1/2 in sized broken bolt. I drilled two holes on each side of it. I was able to get the two halves of the bolt to move and pulled them out. The threads on each side where I drilled got compromised but re tapped it and all is good. Worse part about this it was on the bottom of a piece of equipment and I was working upside down. This had to be fixed one way or the other because replacement was not an option.

 

Got it fixed. It’s not ideal but when I drilled and tapped the holes I wasn’t straight so I had to put the nuts on the bolts to ensure they didn’t run too deep and bottom out. I drilled them out to 3/8” and put stainless bolts in there. I’ve just got to button it up and I’m going to flush the oil cause I had some dirt fall in the lifter valley. I’m so close to having it done and can’t wait. Thank you everyone that commented with suggestions and gave information. This will get me by until I get a 360 to rebuild and drop it in.