sCeRaXn

Well i blew my old LS motor a while back, so i decided to do another simple turbo project. A few weekends ago i tore the engine apart and found that i spun bearing #3 and friend the rings in cyl #1. Anyway, i finally got around to making a new valve spring compressor so that i could tear the head apart. I knew that i had some leaking valves, so i payed attention to the seats as i removed each valve because thats usually where its easiest to spot a leaky valve. After taking them all out i saw that the seats actually looked pretty good, and there was no real sign of a leaking valve. I know i shouldve tested it with the valves in, but i didnt think it was a big deal since it was all getting redone anyway.

Thats when i took a look at the valves and found this. This was the first exhaust valve on cyl 2.

http://www.imagestation.com/3249033/3882313089

The weird part is that there is no damage to any other part of the head. The seat, combustion chamber, piston, cyl walls, and exhaust port are all fine(except for normal wear and tear). I dont understand how this could happen. Ive never seen a valve have a chunk broken off for no appearant reason. I dont see how something couldve been sucked into the motor and not caused any other damage. You would think that it would have atleast scarred up the port or valve seat.

When i took the vc off i immediatley noticed that the head had been rebuilt in the past. There were scratches next to the valvesprings that werent normal Honda tooling marks. It looked like someone used a cheap vs compressor on it and it scarred up the inside of the head. Heres the weird part...the valve almost looks like it was recut after the chunk was taken out because the part that touches the seat was perfectly smooth, and it looks like the jagged edge had been rounded over. The seat couldnt have done that without sustaining some kind of damage.

Heres another twist to the story. A few days before the motor let go i did a compression check and only one cylinder had normal compression...and it was cyl number 2. How on earth could the valve seal with this huge chunk missing? When the valve is closed there is a 1/16th" gap between the valve and seat where that gouge is. This whole situation is mind bottling. Anyone have an idea as to how this happened?

BTW-Heres a pic of the valve seat. Its not a good pic, but you can tell that there isnt any damage to the cc or seat.

http://www.imagestation.com/3249033/3882313099

swappedcx

Sorry, I hate going into a thread and having to click links to see pics. So Ill help the other lazy people like me out.

Jim Truett

That is not a chunk broken off, it was torched off because the valve lash was too tight, and the valve hung open slightly once everything got hot. You were blowing hot gas past the valve. The seat is ok because it gets cooled by the mass of the head.

sCeRaXn

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by swappedcx &raquo;</TD></TR><TR><TD CLASS="quote"> Sorry, I hate going into a thread and having to click links to see pics. So Ill help the other lazy people like me out.



</TD></TR></TABLE>

lol thanks man. I guess i shouldve done that in the first place

sCeRaXn

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Jim Truett &raquo;</TD></TR><TR><TD CLASS="quote">That is not a chunk broken off, it was torched off because the valve lash was too tight, and the valve hung open slightly once everything got hot. You were blowing hot gas past the valve. The seat is ok because it gets cooled by the mass of the head.</TD></TR></TABLE>

That makes sense, but there are a few things that make me think it might be something else. First off, i know that my valve lash wasnt too tight because i set it and re-checked it like 5 different times and it never moved. The last time i checked it was a week or two before the motor let go. The other thing is that the valve doesnt look torched. It looks like something ground into it. Ive seen torched valves before and they show other signs of excessive heat, like discoloration and rounded edges etc.

That was actually the first thing that came to mind when i saw it, but it doesnt look like any of the other torched valves ive ever seen. Im not saying that isnt the cause though. Thanks for the input

JaredKaragen

Well, it looks like the chunk is probably in your cat somewhere...

but that looks like something was definately out of place... when you did your valve lash, did you do it when the motor was literally cold? Adjusting them while the head is even slightly warm (inside) could cause it to happen.

normally exhaust valves are whiteish in color:

sCeRaXn

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by JaredKaragen &raquo;</TD></TR><TR><TD CLASS="quote">Well, it looks like the chunk is probably in your cat somewhere...

but that looks like something was definately out of place... when you did your valve lash, did you do it when the motor was literally cold? Adjusting them while the head is even slightly warm (inside) could cause it to happen.

normally exhaust valves are whiteish in color:

</TD></TR></TABLE>

Yea the car hadnt been started in a week, so id say it was definately cool

Yea ive done a bunch of headwork and ive assembled/disassembled tons of heads, and ive never seen this. Ive seen torched valves before, but they werent near as bad as this one, and it was really obvious that they had melted. This one looks like it was impacted by something else. Oh well, ill probably never know what happened.

The good news is that my buddy is gonna blast the head for me and im gonna start porting it in a couple weeks. I cant wait to see what shell do. Im hoping i can get a radius vj by Brad at RLZ, and if i do then im hoping for around 255-260cfm. Should be good enough for my goals

tony1

Valves usually burn like that when they aren't sealing all the way. Either not enough valve lash or deposits on the seat causing the valve to leak and hot exhaust "torch" it's way through the gap.

Runnerdown

Really tight valve lash will not let the valve cool, because it doest sit long enough to transfer heat to the seat and head. I usually run them a tad looser on turbo motors.

sCeRaXn

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by tony1 &raquo;</TD></TR><TR><TD CLASS="quote">Valves usually burn like that when they aren't sealing all the way. Either not enough valve lash or deposits on the seat causing the valve to leak and hot exhaust "torch" it's way through the gap.</TD></TR></TABLE>

I dont know why i didnt think of that. I knew that the valve lash was good, but i didnt think about deposits causing it to hang open. I guess thats got to be what happened. Thanks for the replies

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Runnerdown &raquo;</TD></TR><TR><TD CLASS="quote">Really tight valve lash will not let the valve cool, because it doest sit long enough to transfer heat to the seat and head. I usually run them a tad looser on turbo motors.</TD></TR></TABLE>

Yea im definately gonna run the valve lash a little looser on this head. What would you recommend, .001-.002 over what that cam calls for? Would the size or profile of the cam have any effect on how much looser to set the lash?