what is the deal with melted exhaust valves? i work on hondas and i cant tell you how many times ive seen it. its always usually in the 3rd cylinder and its always a exhaust valve.. btw, seen this happen on ALL 100% stock engines. what causes this? its happens alot from what i can see.

 

Just a guess, but could it have some thing to do with the design of the coolant channels through the head??

 

i just want to know what causes this to always happen. ive read its because youre leaning out and causing the valves to heat up.. but these are all stock engines though that ive seen this on.

 

i havent ever seen an exhaust valve melted yet...so i dunno. and i got 2 years dismantling in a honda only salvage yard unde my belt as well as time in a repair shop taht did honda only.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by v4lu3s &raquo;</TD></TR><TR><TD CLASS="quote">i havent ever seen an exhaust valve melted yet...so i dunno. and i got 2 years dismantling in a honda only salvage yard unde my belt as well as time in a repair shop taht did honda only.</TD></TR></TABLE>

well i see it ALL the time.

is it because of them burning oil maybe? causing them to lean out?

 

I rarely see it. Are you sure the valve is melted? Obviously, in these motors, #3 runs the hottest, but in stock form, with the stock ecu, not hot enough to melt a valve..

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by locash &raquo;</TD></TR><TR><TD CLASS="quote">I rarely see it. Are you sure the valve is melted? Obviously, in these motors, #3 runs the hottest, but in stock form, with the stock ecu, not hot enough to melt a valve.. </TD></TR></TABLE>

ive seen so many of them and had to fix so many of them... well i guess alot of people call it burnt valves. they get so hot a piece of them chip off and melt. yes they all have been in 100% stock form.

 

Partly because nobody has their valves adjusted.Valves burn because they can't get rid of the heat from combustion.Most of this heat is transferred through the head of the valve to the valve seat.If the lash is too tight the heat can't be transferred.Carbon is a insulator and as this builds up on the seat and valve the transfer is slowed down.The newest gasoline blends are designed to burn cleaner(as in hotter).

 

There are a few reasons that can happen, like NJIN BUILDR said. The face of the valve disperses heat everytime it makes contact with the seat. If the margin of the valve, or thickness of the edge, is too thin, the valve will prematurely overheat, as it cannot transfer heat as efficiently. Valves can wear from incorrect lash, excessive long term high revving, etc. Along with having insufficient margin material, carbon buildup and other contamination can stop the valve from fully seating. Failure to keep up with vehicle maintenance/ tune-ups, improper gasoline usage, and malfunction of certain emissions and hyrdocarbon/NoX controls can lead to carbon buildup. Pretty much any reason that would stop the valve from seating as specified from the factory can lead to overheating. Why you've found cylinder 3 the primary culprit here, I couldn't tell you. I'm still relatively new to the Honda thing, but that's just my .02 $.

 

well that cant be it because i am a regular maintenance freak.. im very **** about my vehicles. i adjust the valves all the time...

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by mike93eh2 &raquo;</TD></TR><TR><TD CLASS="quote">well that cant be it because i am a regular maintenance freak.. im very **** about my vehicles. i adjust the valves all the time...</TD></TR></TABLE>

You mean its happened several times on your own cars?Don't take this personally but its something your doing.Stock honda valves are very tough for a oem valve.Many people use them and make reliable big power.I would set the exhaust valves a touch looser next time around.Not dissing just trying to help.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by NJIN BUILDR &raquo;</TD></TR><TR><TD CLASS="quote">You mean its happened several times on your own cars?Don't take this personally but its something your doing.Stock honda valves are very tough for a oem valve.Many people use them and make reliable big power.I would set the exhaust valves a touch looser next time around.Not dissing just trying to help.</TD></TR></TABLE>

no, not just on my cars. cars that come in to me all the time. i work on hondas.

 

Any Pics?

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by velocitytrends.com &raquo;</TD></TR><TR><TD CLASS="quote">Any Pics?</TD></TR></TABLE>

you dont know what burnt valves look like? ill get some pics i have a couple threw the rest away.

 

you got pm mike93eh2

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by mike93eh2 &raquo;</TD></TR><TR><TD CLASS="quote">ive seen so many of them and had to fix so many of them... well i guess alot of people call it burnt valves. they get so hot a piece of them chip off and melt. yes they all have been in 100% stock form.</TD></TR></TABLE>

ah ok that makes sense now, yeah i have seen the #3 cylidner burn valves as well, usually due to lack of maintaining the car. Just cause its a honda doesnt mean you can ignore it...

 

i have a '93 vtec that melted one of the exhaust valves and the other one was pitted enough after cleaning (all cylinder 3) to be replaced also. Machine shop is grinding valves and resurfacing head, but i don't plan to do anything else before i put it back together. Car has 225k on it and i feel it was pretty well maintained e.g. oil changes(mostly synthetic-on 10k intervals), valve lash right before teardown was withing specs, primarily commuter car all highway miles. But i saw a thread about too tight a valve lash. Should i keep clearance at the upper range of recommended valve lash?

 

Burnt valve:

 

never seen a "melted" valve...

 

I had this EXACT thing happent to my B18C1. The only mod I have is Skunk2 manifold and greddy header and exhaust.