Cracked valves, what do I do now?

[toycar]

What is the advantage of rebuilding this head vs just replacing it w/another junkyard one w/a fresh adjustment? Folks damn near throw F22As away, you could prob get a whole new engine for less than the cost of the labor of rebuilding this head.

Sure, but then you will still have 20 yr old parts waiting to fail.

[DjM_coupe]

H swap time...or just do like everyone else is saying....tear down and rebuild, in the long run you will save money and have an engine good for another 20 years. Take evenings advice and think way is the best thing to do, don't just shun it and go off what you see on Ebay, proper research and quality always wins

[wed3k]

Sure, but then you will still have 20 yr old parts waiting to fail.

with 20 year old machining techniques. everything is a lot more accurate nowadays.

[Mishakol129]

H swap time...or just do like everyone else is saying....tear down and rebuild, in the long run you will save money and have an engine good for another 20 years. Take evenings advice and think way is the best thing to do, don't just shun it and go off what you see on Ebay, proper research and quality always wins

I have already tore it down and am rebuilding the bottom end, this only came up as a surprise. But besides all that, what I want to show you guys now is the condition of the head after some good ol' sanding to get the crud and carbon off. It was very unusual how they had so much crud on them.

Check it out (I added annotations):

[Mishakol129]

too tight of valve adjustment*

loose valve guides can cause a seat to pound around and cause poor seal which in turn not transfer the heat.

f20c/f22c heads have a bad issue with misfire codes>tight valve lash>exhaust seats being pounded>loose valve guides

i always replace them with aftermarket bronze guides. never had an issue after that.

Where are the valve guides located? Are they expensive? Are they hard to replace?

[GhostAccord]

Valve guides are the carbon steel sleeves that the valves slide through. They are pressed into the head. It is usually best for a machine shop to replace these.



However it can be accomplished by heating the head up in an oven @ 150°C (300°F) for 30 min. Then punch/press them out from the combustion chamber side with a 5.5mm valve guide punch/press.

5.5mm Punch


Valve guides removed from head


Ready for new guides


Installation is reverse, heat up the head and chill the new guides. Then press/punch the new guides in to the head from the valve seat side of the head. Press them in to there specified height.

If you are going to go as far as replacing the valve guides I would suggest going with a set of bronzed guides.

[kinguin7]

Sure, but then you will still have 20 yr old parts waiting to fail.

True, I wouldn't expect it to be as reliable as a FULLY and PROPERLY done rebuild, but there are Accords in my u pull that are there because they were wrecked, the engines are most likely still fine, and at 150k, should still have a lot of life left. And despite the wear, you know it was all put together correctly by Honda. And hey, if it does throw something, you're out a couple hundred for another.

OP, you've already seen a rebuilt head go bad after 20k, I'd be surprised if my untouched (afaik) 178k engine doesn't last longer than that.

[wed3k]

the true way for finding a burnt valve would be to take it out, inspect and have it machined. burnt valves often have a low spot if it hasn't cracked through already.