Valve leakage when CCing heads
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From: Mount Dora, Fla
Valve leakage when CCing heads When my friend was ccing his intake and exhaust runners water leaked between the valve and valve seats on a few of the valves. These are newly ported heads with new larger valves, will the valves seat themselves and not leak after the engine is run for a while? I this anything to be concerned about?
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depends on your method..... did you use a little grease between the valve and seat?
if not, do it again .....if so. than you missed a spot!
-spread grease around seat and rim of valve
-install in head and spin a few times..
-wipe away any excess in chambers
this should work perfect.
now when your all done with assembly be sure to VACUM TEST your heads to asure proper seal!
if a port is leaking, just hand lap that valve, and try again! and try again untill ALL
ports are vacum tight!
THIS IS VERY IMPoRTANT!!!!!!!!!!!!!!!!!!! be patient.
if not, do it again .....if so. than you missed a spot!
-spread grease around seat and rim of valve
-install in head and spin a few times..
-wipe away any excess in chambers
this should work perfect.
now when your all done with assembly be sure to VACUM TEST your heads to asure proper seal!
if a port is leaking, just hand lap that valve, and try again! and try again untill ALL
ports are vacum tight!
THIS IS VERY IMPoRTANT!!!!!!!!!!!!!!!!!!! be patient.
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From: Mount Dora, Fla
The point is, is this leakage going to stop once the engine gets running and the valves have a chance to "seat" themselves. I'm worried about power loss because I don't have a good seal between the valve and seat.
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how do you know if you have a bad seal? did you vacum check them? thats the only way you can really tell for SURE....
and yes you can loose power! fix them before you install them!
give some more info on your method of cc'ing and vacum testing first!
and yes you can loose power! fix them before you install them!
give some more info on your method of cc'ing and vacum testing first!
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From: Mount Dora, Fla
Three intake valves are leaking, the worst valve is forming one drop between the valve and valve seat every 4 seconds. Water was used instead of light oil to CC to avoid a mess.
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Verdad Gallardo TECH Fanatic
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From: San Diego, CA
im guessing the heads are fully assembled and you are only cc'ing the CC?
you need to seal the valve with grease to properly cc the chambers.....
if they are allready assembled and they are still leaking! than you need to hand lap what ever valves are leaking untill that are all vacum tight!!!!!!
so are they assembled allready?
you need to seal the valve with grease to properly cc the chambers.....
if they are allready assembled and they are still leaking! than you need to hand lap what ever valves are leaking untill that are all vacum tight!!!!!!
so are they assembled allready?
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From: Mount Dora, Fla
Yes the heads are assembled. The intake and exhaust runner volume is what was being checked. My argument to my buddy is that it's nothing to be concerned about, but he doesn't agree with me. Probably shavings or dirt between the valve and valve seat.
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From: Foley, Alabama-southern Alabama
If those are newly machined heads they shouldn't leak, the builder should have done a vacuum test on them before you got them,I"d call and talk to the shop that built them.Also use rubbing alcohol to cc with it is cheap and easy to clean up afterward plus you can save it and re-use.Use the colored alcohol its easier to see. 
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The leaks are between the valves and the valve seats, not up by the valve seals. The worst one is only leaking one drop every 4 seconds, which is not very much. I don't know the history on the heads other than they are 5.3's and are new with larger that OEM valves. I'm just looking for someone to tell me this is not an abnormal situation and that the valves will seat after the engine has been run.
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when finishing up my heads, while vacum testing them we had 2 valves that had a minimal leak.... so we hand lapped them both, took only an extra 20 min. and now i know for SURE that there good.
best to do it now.
best to do it now.
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From: Mount Dora, Fla
The head was taken to the machine shop and the problem valves were reseated. Interesting point, the porter we were talking to said that he avoids lapping the valves because it messes up the sharp angles of the valve job. Go figure. Never heard that one before.
