Cometic vs Apexi (What causes the Cometic to leak) Please view

[FRSport]

Just to be fair. I've been doing this for a long time from talking with many customers, it seems that a lot people don't properly prepare the head and block before replacing their stock head gasket with a metal gasket. The stock head gasket is a lot softer material so its more forgiving when you have imperfections in the head or block. Metal head gasket requires certain degree of flatness and roughness average in order to seal correctly. Each of these specs are different depending on the design with the gasket. If all this is taken into account, most head gasket on the market (including Cometic) will perform as intended. If any of these things are neglected or done incorrectly, even the best head gasket will fail.

It also seems to me that a lot of people reuse their old head bolts. Please keep in mind that these head bolts warp and stretch under extreme heat and pressure so once its removed, its not recommended to re-use it. ARP head studs is a better (higher specs) and cheaper alternative to the OEM ones available so its recommended that you get that along with your metal head gasket.

[SR'dS13]

Ordered my ARp kit with the cometic! ... Doin' things right, so they get done once!

Just to be fair. I've been doing this for a long time from talking with many customers, it seems that a lot people don't properly prepare the head and block before replacing their stock head gasket with a metal gasket. The stock head gasket is a lot softer material so its more forgiving when you have imperfections in the head or block. Metal head gasket requires certain degree of flatness and roughness average in order to seal correctly. Each of these specs are different depending on the design with the gasket. If all this is taken into account, most head gasket on the market (including Cometic) will perform as intended. If any of these things are neglected or done incorrectly, even the best head gasket will fail.

It also seems to me that a lot of people reuse their old head bolts. Please keep in mind that these head bolts warp and stretch under extreme heat and pressure so once its removed, its not recommended to re-use it. ARP head studs is a better (higher specs) and cheaper alternative to the OEM ones available so its recommended that you get that along with your metal head gasket.

[david200095367]

I bought Arp studs as well from you guys and i had my motor machined. As we see Cometic reversed the part numbers and I have a head gasket made for one oil passage when i need two. So the claim above does not pertain to me.

[Slideways^Jordan]

lol the cometic name cuases it to leak. I dont think you can compare a cometic to an apexi becuase cometic along with cosworthare knock off their just copys of the Greddy Head gaskit.

For something as serious as a metal headgaskit is. Seriously I would go with a real Brand name so I got the Apexi cause its the shiznitt and dont leak plus thats what Enthalpy recommends so i got that over anything else.

Just my .02 cents

[Hijacker]

...along with cosworthare knock off their just copys of the Greddy Head gasket.

I'd like for you to back that up as Cosworth is probably one of the best names I can think of when it comes to quality racing parts. Last I saw, Greddy, HKS, and Apexi didn't have a metric sh1t ton of formula 1 wins under their belts. Cosworth has put some actual R&D into their products and have turned out a very nice product. Also, if memory serves correctly, Greddy headgaskets aren't 4 layer, nitrile rubber coated like the Cosworths are.

[sr20goofus]

lol the cometic name cuases it to leak. I dont think you can compare a cometic to an apexi becuase cometic along with cosworthare knock off their just copys of the Greddy Head gaskit.

For something as serious as a metal headgaskit is. Seriously I would go with a real Brand name so I got the Apexi cause its the shiznitt and dont leak plus thats what Enthalpy recommends so i got that over anything else.

Just my .02 cents

Cosworth is most likely NOT a knock off, deff a rookie response when everyone knows Cosworth is top notch quality, well above greddy APexi and any other JDM company.

Maybe i am one of the freak Cometic cases, but i have NEVERE had a headgasket leak or fail in all the motor swaps ive done for people, i always use cometic, never use copper spray or RTV. Usually when i put a headgasket on though i look at it sitting ont eh head to make sure everything lines up, its an easy way to be sure you wont have to pull the head 3 times.

My current headgasket has been in for 2 years with nothign but roadracing track time on the engine and without a single fault, i have no reason to discredit cometic.

[Hijacker]

Cometic has been hit and miss from what I've seen over the years. Also, after talking with a friend of mine who has been wrenching for 30+ years, he's come to the conclusion to make a metal headgasket seat well on a Nissan, the head needs to be retorqued after the break in period. He's done a few L series recently that upgraded to metal head gaskets and out of them, the one he didn't retorque leaked.

That's of course in junction with having both the head and deck checked for straightness

[david200095367]

i dont know if you read everything but its not a mechanical error on my part. Cometic has the part numbers reversed and they have been sending the s13 gasket with one oil passage to s14 sr owners that have 2 oil passages thus causing it to leak oil because there is no seal around the 2nd oil passage.

Like I said i had it resurfaced and even used silicone.

Edited for uncalled for namecalling. -Hijacker

[Slideways^Jordan]

I'd like for you to back that up as Cosworth is probably one of the best names I can think of when it comes to quality racing parts. Last I saw, Greddy, HKS, and Apexi didn't have a metric sh1t ton of formula 1 wins under their belts. Cosworth has put some actual R&D into their products and have turned out a very nice product. Also, if memory serves correctly, Greddy headgaskets aren't 4 layer, nitrile rubber coated like the Cosworths are.

yeah your right im sorry i cant back that up im sorry for posting that with out thinking twice lol. I guess i mainly said that cuase if you look at the pics posted above of the cosworth greddy and cometic gaskits to me they look very similar in desighn so im sorry for saying that im kinda a noob to the whole Metal head gaskit thing. This is my first time useing a metal headgaskit and when ever i talked to scott at Enthalpy he recomend that i use the Apexi metal head gaskit for my build so thats thew one that i got.

I hope you can understand what i mean

As for Cosworth i really dont want to sound like im putting them down i need to do some background check on them , but one thing that i really like about cosworth is that they use the nitrile rubber on their headgaskits like you said. So it like a ultimate seal once the head gaskit is tourqed.

But ive heard people haveing bad expierence with cometics and that just gives me the chils.

[Hijacker]

It's fine. Just saying things like that is how bad rumors get started.

[justjuiceit4]

I'd like for you to back that up as Cosworth is probably one of the best names I can think of when it comes to quality racing parts. Last I saw, Greddy, HKS, and Apexi didn't have a metric sh1t ton of formula 1 wins under their belts. Cosworth has put some actual R&D into their products and have turned out a very nice product. Also, if memory serves correctly, Greddy headgaskets aren't 4 layer, nitrile rubber coated like the Cosworths are.

A quality head gasket does not have to be 4 layers. In fact the original Viper head gasket was 7 layers to account for all the head lift that the engine had during testing. Chrysler got the tolerances in the engine better to reduce the amount of layers. There are a lot of quality OEM head gaskets that are just two or three layers. I worked as a product/test engineer for a major supplier of OEM head gaskets. You would not believe how much testing and research goes into producing a quality head gasket. Well, let me rephrase that, with a crappy tolerancing and finishing (domestic) engine a lot of design goes into sealing it.

As far as the Cometic head gasket, I was not impressed with my experience. When I was working with my former job, the engine shop guys were building some race engines. The engines had some leak issues with the head gaskets. Being that these guys assembled engines for their job, I assumed that they properly prepared the surfaces and used the correct torque sequence/values. They asked me what they should do. My first suggestion was to use a gasket from my former company, but they had a non-standard bore IIRC. My next suggestion was to increase the torque value of the head bolts, but they were at the max already. So, they got some ARP bolts, increased the torque and the problem was solved. However, the gasket should have sealed with stock torque values. That is the main problem with too many suppliers is they produce the bare minimum. One gasket that I was working on that was so robust with N/A application, it was used with the forced induction version with no changes! Thats a "quality" supplier can do for you!

[Hijacker]

A quality head gasket does not have to be 4 layers

I was more or less just trying to establish that the Cosworth gasket isn't a copy of the Greddy gasket. However, I do believe that the extra layer on the Cosworth does play a factor into it's sealing pressure. The report that sold me on the cosworth was one done by Eric Hsu (used to work for XS Engineering, now he works for Cosworth). He posted up some pressure film tests done on a mitsu 4g63 out of an evo between the OE multi layer, a cometic, and the cosworth. The cosworth sealed tighter across the board than the OE and cometic. The big thing about that little test is that it showed that the cometic failed to seal in the proper places.

Your story does go to show just how important head studs are to making a head seal properly. I find it surprising that an engine shop was building a race motor using head bolts, though. That would be one of the number one things that would go on my build list if I were working at an engine shop. The local machine shop I use for all of my motor work here in town use nothing but ARP hardware for just about everything.

I do like what corky bell said in his turbo book "You won't find a better gasket than what came in it stock". I like to believe that on many levels. They seal better, and if you're blowing head gaskets, then you obviously have a problem and putting a metal head gasket in is nothing more than a band aid fix. If it were possible, I'd o-ring the block and leave the stock head gasket on, but that wasn't an option for my block.

[justjuiceit4]

Just to be fair. I've been doing this for a long time from talking with many customers, it seems that a lot people don't properly prepare the head and block before replacing their stock head gasket with a metal gasket. The stock head gasket is a lot softer material so its more forgiving when you have imperfections in the head or block. Metal head gasket requires certain degree of flatness and roughness average in order to seal correctly. Each of these specs are different depending on the design with the gasket. If all this is taken into account, most head gasket on the market (including Cometic) will perform as intended. If any of these things are neglected or done incorrectly, even the best head gasket will fail.

It also seems to me that a lot of people reuse their old head bolts. Please keep in mind that these head bolts warp and stretch under extreme heat and pressure so once its removed, its not recommended to re-use it. ARP head studs is a better (higher specs) and cheaper alternative to the OEM ones available so its recommended that you get that along with your metal head gasket.

Actually, there are several OEM head gaskets that are MLS (mulit-layer steel). However, some manufacturers such as GM have a lot of applications that cannot use MLS gaskets due to the rough surfaces/imperfections, etc. in their blocks and heads. Proper prep of the block and head is very important. You would be amazed though with some head gaskets....one of the tests I did was put several large metal shavings between the gasket and the mating surfaces. The shavings had to be very long, really thick and near an oil passage for the gasket to leak.

I would never reuse head bolts. We would torque bolts three times for static tests and throw them away. Note that your engine is not static if you are driving! I would invest in a very high quality torque wrench and make sure its calibrated. I agree that studs are a less expensive quality upgrades.

[justjuiceit4]

However, I do believe that the extra layer on the Cosworth does play a factor into it's sealing pressure. The report that sold me on the cosworth was one done by Eric Hsu (used to work for XS Engineering, now he works for Cosworth). He posted up some pressure film tests done on a mitsu 4g63 out of an evo between the OE multi layer, a cometic, and the cosworth. The cosworth sealed tighter across the board than the OE and cometic. The big thing about that little test is that it showed that the cometic failed to seal in the proper places.

I do like what corky bell said in his turbo book "You won't find a better gasket than what came in it stock".

The extra layer could increase the static sealing pressure, if he used the Fuji film testing method. However, the correct design of embosses should produce all the sealing pressure an engine needs. Speaking of OE gaskets, not all are quality gaskets as our competitors had interesting ways of making their product look better than ours (rather complex explanation) and the manufacturer definately gave our competitor a huge advantage during dyno-testing. I am pretty sure the company I worked for does not produce the 4g63 gasket. so I can not speak for whoever produces that gasket. In fact not a lot of design went into the foreign head gaskets that they id produce.....since the tolerancing/machining of the engines was so good! In reality they just gave us a drawing and were like "make this gasket"! haha Their head gasket design was inferior to some domestic head gaskets, but like I said before, the head gasket was not a band-aid to fix manufacturing errors.

As far as the head bolts they used....these engines and parts were provided by the manufacturer IIRC, so they were just trying to save some money by using the parts they already had. In all the other applications they dealt with, the factory head bolts worked fine.....which they would with a "proper" head gasket.

I disagree with Corky about that last statement. The 3.8 liter head gaskets found in Ford engines were HORRIBLE. People bought the gaskets in packs of 6 or 12! hahha

[Hijacker]

I disagree with Corky about that last statement. The 3.8 liter head gaskets found in Ford engines were HORRIBLE. People bought the gaskets in packs of 6 or 12! hahha

You do have to remember that Corky was generalizing for a large industry. I wouldn't trust the headgasket in a dodge k-car to hold ambient air pressure let alone boost pressure. However, a lot of blown headgaskets in the turbo world develop due to fuel mixture issues. I've seen SRs produce good, durable power on the stock head gasket because the fuel mixture was correctly tuned.

I do see where you're coming from and metal headgaskets are a necessity past a certain point. I'm just offering up the other side of it all.

[schanne]

I had a cometic put in on my stock rebuild. My builder was nice enough to use the stock studs so of course I have leakage! I won't be buying a cometic after this anyway, regardless of not putting in arp studs in the first place. Cometic for me= FAIL My builder= FAIL x 1000

[Slideways^Jordan]

It's fine. Just saying things like that is how bad rumors get started.

oh yeah thats tru.

[david200095367]

I had a cometic put in on my stock rebuild. My builder was nice enough to use the stock studs so of course I have leakage! I won't be buying a cometic after this anyway, regardless of not putting in arp studs in the first place. Cometic for me= FAIL My builder= FAIL x 1000

Agree!