So both of my 2000's blew headgaskets in the last two weeks, both to the outside of the engine. 220k and 230k on the clock. One of the two I replaced the HG myself at around 180k with the Fel-pro gaskets, so I am definitely disappointed to have to do it again. The other one had the HG done at a shop at about 150k according to the PO, not sure who made the HG yet, will have to wait till I get it apart. Has me wondering if anyone has ever had a Cometic hg blow - not related to overheating of course.

 

You know I want to know too.
I'm really leaning towards cometic head gaskets for my rebuild.
So far NoDoubt has over 7000 miles on his.

I will use ARP head studs this time too.
I'de just be more comfortable knowing everything has been set at the same torque. Vs torque to yeild bolts with an angle gage. The stretch bolts work, but I'de rather spend a little more at this point in the hopes of a better seal.

 

 

Mine are good so far, but that is just 3000 miles.

Honestly, you'd be fine with Elring, Fel-Pro or another good brand. That is what my machine shop recommended. The elring's I had were fine, just the valve stem seals started leaking. That said, the Cometic are 100% metal which will give a really consistent mating surface vs the hybrid, and they also lack the texturing that puts dimples in the mating surface as well.

There is minor trimming or bending of tabs on the Cometic's that you'll want to be prepared for.

They also have a tech support number you can call and they will answer any questions that you have. I just got the Cometic HGs out of the feeling that I needed to get it absolutely right the second time regardless that the failure wasn't my fault on the first attempt.

Have I mentioned change your valve stem seals?

 

Was running 170 degree stats in both at the time.

 

 

Extinct uses a different thermostat and housing for the 170, he has pictures of them here.

 

Check the block for trueness. Did you have the heads decked when the gaskets were replaced? TTY bolts work fine, I've used then several times with no failures so far. ARP studs are nice, but pricy and unnecessary.

What actual temp were the trucks running at? Just cause they have 170 stats doesnt mean thats the temp the truck is running at.

Single layer gaskets are used in race applications, especially in vehicles running a lot of boost/nitrous/etc, which are disassembled often. Multi-layer gaskets are a huge improvement for street vehicles. Most vehicles used to run single layer steel gaskets. The Multi-layer gasket was invented because of the short lifespan of the single layer gaskets.

 

 

Read my sig - 10 discos in, currently have 5. Not my first rodeo, although I have not used Cometic head gaskets yet in the 4 previous HG replacements I have done. Not asking why they blew, or how to prevent them from blowing, just wondering if anyone has actually had a Cometic hg blow.

For the curious, the truck I personally replaced the HG on - I don't remember ever overheating it. It was running in the 170 range typically using the bypass thermostat mod, I run a Innovate Motorsports MTX-D 3913 dual display water temp and oil pressure gauges. The other truck was overheated twice (blown hose, and way too steep grade pulling another Disco on the trailer) and was drinking a small amount of coolant as a result, however the death knell was the exterior blow whereby it started losing compression at a rate that began triggering misfires. That one did not happen as a result of the overheat, happened double digit weeks later. BOTH trucks were exterior blows, not water jacket blows.

Now, any cometic HG users ever blow one?