MHG vs Cometic

[Greyscorpion]

Im sure that this has been talked about I did a quick search to find some info but its late, so if someone can post a link on the pros and cons of cosmetic. I know that MHG is the way to go but im not looking to go crazy with the boost on this engine it has 141,000 miles and as far as i know the head gasket hasnt been replaced but its holding up just want to get it done and over with before i have any issues.

 

[KicknAsphlt]

Cometic IS a MHG....

 

[Greyscorpion]

Cometic IS a MHG....

my bad I for some reason thought that there was a difference

 

[Greyscorpion]

I guess that this topic will be found in the wall of shame

 

[steven89]

Not quite. The Cometic if I remember correctly, doesn't require AS smooth of a machined surface (different RA specs for the different MHGs). Ive always heard that the Cometic are THE MOST forgiving MHG. I've heard of a few people being able to run the Cometic without any machine work and just a REALLY good cleaning job on the stock surfaces, but I took that as a grain of salt. As I didnt use a Cometic when i did my HG, cause I didnt get it machined. I just really didnt want to take it apart again to fix the Cometic if it leaked or blew again.

 

[Greyscorpion]

Not quite. The Cometic if I remember correctly, doesn't require AS smooth of a machined surface (different RA specs for the different MHGs). Ive always heard that the Cometic are THE MOST forgiving MHG, although I took that as a grain of salt. I've heard of a few people being able to run the Cometic without any machine work, and just a REALLY good cleaning job on the stock surfaces. I didnt use a Cometic when i did my HG, cause I didnt get it machined and I didnt want to take it apart again to fix the Cometic again if it didnt work..

Thats the questions that I was looking for answers for, was there a difference between them or would I have to get it machined if so Ill just go with an oem replacement clean it up like I would normally and call it a happy f...ing day

 

[steven89]

Yeah the RA spec is different, and the Cometic "smoothness" (or RA spec) requirement was less than any of the other MHGs. Honestly id get it machined with ANY MHG, if you cant then go stock or similar. haha

But when I did my headgasket, I literally spent like a full day cleaning the head/block; a bit unnecessary but I didnt want it to blow again. I made my own brass scraper, and I had it very clean. I actually got suggestions in my build thread when i did my HG that I should/could go Cometic. But yeah, I ended up with a Fel Pro gasket (looked of same/better quality than Toyota) and ARP head studs at 95 ft lbs. Got those tq specs from someone on the forum that seemed reputable at the time of doing the HG, I know it seems high compared to what people say to use but it worked for me.

 

[Backlash2032]

I also believe the Titan head gasket is also just a rebranded cometic.. for a lot cheaper too.

Sent from my HTC Rezound using Tapatalk 2

 

[Greyscorpion]

So if I'm reading this right with the cosmetic MHG you don't technically need to deck the head and block at a machine shop just clean it really well like I normally would

 

[supra34]

Not sure if I'm the only one here that noticed that he said cosmetic not cometic head gasket lol I think at the beggining he was meaning stock head gasket vs mhg because he has a lot of miles and not really running a lot of boost. But who knows I say go with metal head gasket just Cuz you will probably eventually want to go with more power even if it does have more miles on it.but if you really don't ever plan on it then use a good stock one like felpro or even the cometic one with a clean head and block

 

[radiod]

So if I'm reading this right with the cosmetic MHG you don't technically need to deck the head and block at a machine shop just clean it really well like I normally would

If you're not going for crazy boost (like you said in your first post) stick with a stock Toyota gasket. When torqued properly with proper hardware they'll easily hold 300whp which sounds like what you're aiming for, and they are the most forgiving in terms of prep. If the surface has not been machined since the factory on a 141k mile engine I'd be more inclined to get it machined before slapping on even a Cometic MLS gasket. Basically are you willing to gamble tearing the engine apart again and doing the job over again vs. the trouble of pulling the block and doing it all "right" the first time?

 

[supra34]

He is right its a gamble your gonna have to take if you don't get it machined but if you for you might as well just get a mhg

 

[jake8790]

I think you got composite confused with cometic. composite is the factory style head gasket. you need to run one if you are not getting the block machined. have the head machined either way.

 

[KicknAsphlt]

Not quite. The Cometic if I remember correctly, doesn't require AS smooth of a machined surface (different RA specs for the different MHGs). Ive always heard that the Cometic are THE MOST forgiving MHG. I've heard of a few people being able to run the Cometic without any machine work and just a REALLY good cleaning job on the stock surfaces, but I took that as a grain of salt. As I didnt use a Cometic when i did my HG, cause I didnt get it machined. I just really didnt want to take it apart again to fix the Cometic if it leaked or blew again.

There have been a few guys that I know of in the Dakota R/T world that have run Cometic gaskets without machining the block/head surfaces for a specific RA spec and those things leaked like a sieve...they ended up cheating and spraying them with that gasket sealer spray (yeah...bad, I know).

 

[Greyscorpion]

Thanks and I thought that there were two different types of MHG one that was a but more forgiving and then one that needed to be machined but yes I think that I'm going to go
With the fel pro thanks guys

 

[Greyscorpion]

I'm only pulling the head because number six has a bad exhaust valve

 

[supra34]

Alright just make sure its very clean and use a straight edge and make sure its straight and torque to the right specs and you should be good just don't ever over due the power and boost or you will be taking it apart again lol good luck

 

[AJ'S 88NA]

^Most people don't have a good enough straight edge to check, anyway should have the head surfaced, and checked out.

 

[Turbo Habanero]

Don't do a metal head gasket if your not willing to get the head and block surfaced unless you want to do again...

I'm running 18psi and have been up to 22psi on a 60-1 turbo on a stock Toyota head gasket with arp head STUDS

P. i will add my car is a daily driver and sees a lot of abuse and track time.

 

[supra34]

Really that's crazy that's a lot for stock gasket