So thursday i parked my truck and tore it apart, installed my 6.0 i just cammed, put ls7 lifters in, pac 1518s, and 317s milled .035 along with a 4 angle valve job. i used factory gm mls gaskets. AJII was there and we started the truck, aj saw that i was leaking coolant from the #4 cylinder onto the header primary. it wasnt spraying out but dripping. after it ran for a minute while we were trying to determine where the leak was coming from it also starting smoking white, showing that it was leaking into the cylinder as well.

today i pulled the head off and didn't see any obvious causes for the leak, but i noticed the lines on the gasket where you could see it sealed, right around the bottom of the #4 cylinder theres about an inch where you can't see the line like it sealed properly as you can on the rest of it.

I am going to have the head checked by the guy that milled it. he is probably going to say it is fine, so im gonna have it checked by another machine shop as well. if they both say its ok, what could be the problem? the block is clean and smooth. could i have just gotten a bad gasket? i torqued everything to spec in the correct sequence also

 

I know you said the deck on the block was clean, but make sure it is 100% clean. I carefully kept scraping with a razor blade, and was amazed at what still came off. Did you ever run this engine? Are you 100% sure the block is good? Also it might be a long shot, but by any chance did a head bolt get tightened down with fluid in the hole? It may have cracked the block. If you have the ability, apply pressure to the coolant system before you start it next time. That's all I can think of off the top of my head right now.

 

X2 on making sure its clean

 

Well replaced the head gasket and had the head checked today. Heads fine. Problem still exists. Aj looked at it today while I was at work and said it looks like coolant is coming out of the exhaust ports ( header was loose). I suppose this could be a headgasket or cracked cylinder wall.

 

if its coming out of the exhaust port then the head is cracked.

 

Are these heads ported? People have been known to go into a water passage if they remove too much material.

 

not ported but milled, yes


anybody got a 317 milled .035 i can borrow?

 

a 4 angle valve job was also done, i don't know how close the water jackets are to the valve seats but thats a possibility as well i guess

 

His latest findings he posted on another board..

pulled the header and spark plugs, blew into the overflow tank and coolant poured from the manifold bolt holes. i put bolts in the holes and the cooland started pouring from #4. the bolt holes pouring coolant makes me think someone put longer bolts in or something at one point in time and cracked the water jackets just enough to come out of the holes on some and then enough to crack the jacket into the exhaust port on #4, i am going to do more pressure testing to make sure its not the block tomorrow, but i am really thinking its a crack in the head. i didn't even have to blow hard and it flowed pretty good. i'll make a vid tomorrow if possible.

 

Good luck, keep us posted.