why do engines blow head gaskets?

[Banjo]

Just like it reads, I've always heard of it and have seen it, but wonder what causes it and I truly don't know. Once one blows a head gasket, does that automatically mean a rebuild is in order??? Reason I ask all this, I just opened up a V-8 and on the pass read, I knew the headbolts were coming out wet (whereas the rest had been dry) and once I cracked the cylinder head loose, antifreeze type dirty water poured out and as I gazed down on that piston, it had cottage cheese on it. The one next to it was fine. And, I began to think this low mileage motor that was just going to get regasketed before being inserted into a chassis might need to go to machine shop and then I began to wonder exactly why do head gaskets blow? Over heating? Over revving? timing chain stretch? Loose head bolts (these felt like 160 foot pounds if they were an inch, they were heck to get loose)? Warped head or warped block? Cracked head or cracked block? What think YOU. I know I'm not that sharp on engines, so I'm humbling myself by admitting I truthfully don't know what head gaskets blow.

[JMcTurnan]

I know over heating and over revving can do that, but I've replaced many head gaskets and never rebuild an engine. It drives fine, works how it did.

[fordman]

it can be loose head bolts warped heads cracked heads. junk in between the gasket when it ws first put on. or it could just be a weak gasket that gave way. depending on what is all found wrogn . head gaskets can soemtimes just be replaced and keep going. no need to tear something all the way down and do a total rebuild for just a gasket. but that is always not the case. while the head is off why not get it checked for cracks and warps? maybe the heads are due for a valve job at the same time. if the engine did over heat look out. check everything. did the oil have water in it? did the water have oil in it?

[towtruckerfour]

This is the issue I am dealing with right now. I have 2 cylinders next to each other with low compression which is usually a head gasket gone bad. I am probably going to pop the head and see what I got. I need the truck back running but don't have the money for a full overhaul.

[dustman_stx]

I just blew a head gasket on a 390 with 500 miles on it. Compression ration is a little better than 10:1, and I was running it pretty hard. I, in my infinite wisdom, didn't replace my head bolts, and a buddy of mine that's pretty keen on engines thinks they probably stretched. Blew between cylinders 1 and 2. I'm thinking of running the Cometic MLS gasket, but that sure is a lot of money..$200 for the set. Worth it?

[towtruckerfour]

I just pulled the head off my 302 and found the gasket broke between 1 and 2 on the driver side. Now I have weekend plans.

[Banjo]

This engine had thin metal head gaskets, stock, and had never been open (supposedly). Head bolts very tight. water in only 1 cylinder, leaving cottage cheese type substance in there. But, upon cracking the engine open the smell was PUTRID. So, I'm going with the overheating (burnt oil).

[fordman]

I just blew a head gasket on a 390 with 500 miles on it. Compression ration is a little better than 10:1, and I was running it pretty hard. I, in my infinite wisdom, didn't replace my head bolts, and a buddy of mine that's pretty keen on engines thinks they probably stretched. Blew between cylinders 1 and 2. I'm thinking of running the Cometic MLS gasket, but that sure is a lot of money..$200 for the set. Worth it?

back in the day. head bolts were always reused. newer engines are the ones that came up with the replace the head bolt thing. its the way its been. they may have made head bolts back inthe day. but i never replaced them. i just reused them. what head gasket did you use before?

[OldRedFord]

FWIW I am reusing the head bolts on me 460 build. Judging by the ford part #s on the head gaskets and the dates and FoMoCo and the date 6-75 on all the bearing shells I am the first one to go inside the engine since it left the factory.

[ToughOldFord]

I've always reused head bolts in older rigs. The 'stretch bolts' is something relatively newish.

Of course I don't build 500HP monsters either, maybe it's good practice with those.

[thebannister8]

be sure to follow proper bolt pattern tightning and torque values

[dustman_stx]

be sure to follow proper bolt pattern tightning and torque values

I did. And after reading a few posts here, I'm questioning the head job. I've been giving more info on the Cometic MLS... forum topic I started. Might help some others experiencing head gasket problems, too.