Cometic Head Gasket layers have parted

[rossmac]

Can somebody confirm that this is a cometic head gasket?Also the layers have come apart, does this matter or can it be re-used?

Also ive attached a picture of the block both bores & the machined surface,Does that look finished to a high enough standard to acomidate a cometic?

Do the bores look finished properly? they look very course to me however you can really feel the lines .Thanks gents

[rossmac]

sorry gents have another question,Can i use the standard h/g if im running around 400 bhp?Whats the advantage of a cometic? i know you have to get the block & head surfaced so they can seal properly to the gasket, but my thoughts are, if a standard hg will work then why go tothe extra cost ?

[float_6969]

It looks like a Cometic to me.

They layers are fine separating like that. There isn't anything to hold them together except for those rivets.

To me, that head surface looks too rough for the Cometic.

The cylinders look alright to me, but you shouldn't be able to feel anything in the cylinders.

Boost_Boy has used the stock HG to 500HP w/o a failure. I should be near the 400HP mark with my setup and I am using a stock HG as well.

[rossmac]

So whats the advantage of a cometic if runnding around 400 bph?

[float_6969]

You can re-use it? that's about it AFAIK.

[KEMP]

well IMO, the block needs decked, or atleast skimmed, it should be almost shinny, not dull, have it checked and decked, along with the head, using a cometic without decking the block and head, will end horribly.

personally i (along with some others on here) have had problems with the cometic sealing at the back of the block. and make sure you check aroung the cylinder holes on the gasket to make sure its not cracked, last week i was helping my buddy with his SR20 and we were reusing the cometic, and while i was looking it over i saw a hair-line crack around one of the cylinders on the top layer of the head gasket, so we threw it out and used a felpro.

i on the other hand, recommend Greddy/Grex head gaskets, because ive never had one leak, but the only problem is, i bought the last greddy head gasket for a ca18 yesterday, until they make a new batch around april, i was sitting there at a local shop when he was on the phone with greddy, lol, so im sorry. but felpro will work fine, just deck the surfaces, and do wht you want with the head gasket decision.

but i would suggest hot tanking the block, it looks a little gross, but thats me, i clean everything and want everything to look great.

good luck on the build.

[rossmac]

Cheers dude, yeah its definatly getting cleaned up before it goes in my car! what chemicals are used in hot tanking?

[boost_boy]

Honestly,

That block has been machined before and if you didn't over-heat it, clean it up with a mild abrasive pad and spray copper spray onto the cometic and then it should be useable again. For anything under 500hp, the stock headgasket is better than good enough. Only use the cometic if you don't have access to a standard one. Too many people have screwed-up the install with cometic units which result in them blaming the gasket and not the installer.

Dee

[rossmac]

I dont know if the block's been machined smooth enough for the cometic which im concearned about

Honestly,

That block has been machined before and if you didn't over-heat it, clean it up with a mild abrasive pad and spray copper spray onto the cometic and then it should be useable again. For anything under 500hp, the stock headgasket is better than good enough. Only use the cometic if you don't have access to a standard one. Too many people have screwed-up the install with cometic units which result in them blaming the gasket and not the installer.

Dee

[MeanGreenS13]

nothing wrong with a cometic gasket, just needs proper install. I f***ed up on mine and still have it hanging around in my garage. Because of the bad rap they have gotten, I cant seem to get rid of it... its still good too! good luck!

[bentvalves]

too many people have had issues with cometic gaskets to write it off as user error.

more engines that just ca18 to boot.

[float_6969]

And most of the sealing problems of the Cometics come from the engine builders not decking the blocks and heads to the correct roughness.

[mbmbmb23]

And most of the sealing problems of the Cometics come from the engine builders not decking the blocks and heads to the correct roughness.

Please elaborate.

[float_6969]

From Cometic's website;What surface finish is required to us an MLS head gasket?A surface finish of 50 RA (roughness average) or finer, is recommended for a proper gasket seal. Anything rougher may conflict with the gasket design.

[boost_boy]

too many people have had issues with cometic gaskets to write it off as user error.

more engines that just ca18 to boot.

The funny thing is, we don't know the condition of their blocks, heads, machinist's capabilities, etc. etc. In the end, it's just layers of steel that if properly installed onto the properly prepared surfaces, should be good to go. I've installed cometics on decks I've cleaned-up myself and they seal just fine without the infamous leaks they're accused of causing. Again, user/installer error. And if I had screwed-up personally in that area, I'd be one of the first to blame my idiocy for the screw-up. I can only blame cometic if there was a design flaw in which I've seen none so far and the reason I know this is because I used to buy the cometics from members on this forum who had failed installing their cometics; which are now in other folks' projects mind you.

Dee

[r34 gtr]

I think I am with Dee on this one. I got a NISMO MLS head gasket from him and it leaked in the same place as all the Cometic gaskets do because I did not properly prepare the mating surfaces. Installer error there, and nothing but. My head/block surface was drat close to being flat too. So close I was in disbelief that it would leak. All it takes is one or two thousandth of an inch and you are SOL.

That being said I would still never buy a Cometic gasket, but that is just personal preference. Copper treated stock HG's are cheap and awesome.

[bentvalves]

stock headgaskts have a better chance of sealing mating surfaces that are slightly out, that and the fact that they CAN handle lots of boost pressure makes them a perfectly reasonable option.

I will upgrade to a MLS one day, but that is becuase I usually have the head off 1 time a season and buying new gaskets is getting expensive.

[dash]

I'm surrounded by friends that run metal head gaskets on various motors. NONE of them has ever removed their block or had it decked. Street cars, that see 30-40psi at the strip, no failures!

why should one have to go thru all that crap to run a cometic on a puny ca18 ? Foolishness imo.BTW, a handfull on sxoc never decked their block. Cometic didn't leak. Still too main issues for the majority tho. I wouldn't go near the pos

One neighbour recently had his stock bore RB25 pistons actually "hit" the cometic. Couldn't pinpoint the "rapping" noise, had to disassemble to determine. That is garbage. Poor quality control

Quote »Boost_Boy has used the stock HG to 500HP w/o a failure[/quote]with all the dismal negative posts here, why has this setup been kept 'secret' ?We could use some positive CA18 news around here for a change. Deserves a detailed build thread of its own ....or did I miss it ?

[boost_boy]

with all the dismal negative posts here, why has this setup been kept 'secret' ?We could use some positive CA18 news around here for a change. Deserves a detailed build thread of its own ....or did I miss it ?

Everyone wants to have a build thread, so no need to over-shadow some of these folks' efforts. The problem I got is, the recipe is simple and have posted it years ago. Some will borrow bits and pieces and some go their own routes which is their choice. I don't live at a dyno because I'm not having the issues that most have. Most don't want to spend the money to buy some of the equipment I use and with that, I respect them for it. Some just don't want to be a follower and that's cool with me. I definitely know what I'm doing with this motor and do share my successes and some failures. But there are members on this forum that have their own visions and I strongly encourage them to follow their visions. And when they fail, don't be afraid to share that as well. Some of the guys want help and some have magical friends that can do this and that and I say "to each his own".

To be honest, build threads are boring to me; especially when it's just a regular rebuild. "meminto's" thread is more of a reconstructive fun build, but at least it's not just a rebuild of regular CA parts and a T2small turbo and a ebay manifold (played-out). Time to get aggressive and when the opportunity presents itself, I'll let a few more things out of the closet.

Hot news: I completely over-heated the B13 sentra's CA as well as (I think) ran the car low on oil or something. Think I screwed-up my GT35R snail and I know the motor is low on compression, but that's what I get for not wanting to stop on the highway when I sensed something was wrong. Oh well, it's very easy for me to rebuild the motor and go buy a new $1300 turbocharger, but that car can sit for a long time as I have other cars that concern me more.

Dee

[r34 gtr]

I would cry if I ruined a $1300 turbocharger because I didn't feel like pulling over to check. Just wanted to say this.

[boost_boy]

I would cry if I ruined a $1300 turbocharger because I didn't feel like pulling over to check. Just wanted to say this.

Update: Per my hairdryer supplier, the GT35R is good-to-go. But the engine, well, you can smell the burn engine before you get to the car. The oil has been completely cooked and I think the highest compression reading was 60psi (Great). I wasn't being lazy, but I wasn't going to pull over on the very busy turnpike either which subsequently will need me to do surgery on the motor. It won't be stock when it comes back , which shouldn't be too long as I'm done rebuilding my 240's CA.

Secret: It now sports some JUN cams and valve springs that are much stronger than Tomei's. To be continued in another thread.......

Dee

[boost_boy]

I would cry if I ruined a $1300 turbocharger because I didn't feel like pulling over to check. Just wanted to say this.

Update: Per my hairdryer supplier, the GT35R is good-to-go. But the engine, well, you can smell the burn engine before you get to the car. The oil has been completely cooked and I think the highest compression reading was 60psi (Great). I wasn't being lazy, but I wasn't going to pull over on the very busy turnpike either which subsequently will need me to do surgery on the motor. It won't be stock when it comes back , which shouldn't be too long as I'm done rebuilding my 240's CA.

Secret: It now sports some JUN cams and valve springs that are much stronger than Tomei's. Oh yeah, a NISMO 1.2mm metal headgasket with ARP head studs to secure it all. To be continued in another thread.......

Dee

I would cry if I ruined a $1300 turbocharger because I didn't feel like pulling over to check. Just wanted to say this.

I did cry for a while, but now I'm happy again.

[dash]

Quote »To be honest, build threads are boring to me[/quote]yeah, I hate "build threads" also. Showing a bunch of photos of parts.... when really, it all means absolutely nothing until (or if) a successful result is attained imo. 500hp street CA18 is a 'successful result'

Quote »The problem I got is, the recipe is simple and have posted it years ago[/quote]a few questions;So 500 on stock (or felpro) head gasket. Was this a stock piston motor too ?Same colt cams ? 60-1 t3/t4 ? what psi ?what was the peak torque like ?I recall u posted punishing a CA18 street S13? @ 30psi... was this the car ?30 on pump gas, or do u dial it back a bit for the street ? or use water/meth/alch inj ?

Just curious about the various paths folk take, and trying to define some limit of components.Obviously you're on top of your tuning game

[boost_boy]

a few questions;So 500 on stock (or felpro) head gasket. Was this a stock piston motor too ?

This is on a stock motor with stock oem headgasket straight from a Japanese junkyard (unopenened).

Same colt cams?

Indeed. I have just replaced the colt cams with JUN pieces just because I'm going to a smaller turbo.

60-1 t3/t4 ? what psi ?

Correct. I started out with a Turbonetics 60-1 (partial ballbearing) turbocharger and it makes good power past 5000rpm. But it was just too late for what I needed and when I needed it, so I opted for a Garrett 60-1 dual ballbearing CHRA, modified my rear housing for the P-Trim wheel and it felt like the Turbonetics unit. So now, it has been returned to my supplier and I will now give the GT30R a swing. Unfortunately, it wasn't ready for me today, so I won't be able to do any testing until later this weekend or sometime next week.

I ran a max 25psi of boost on the turbonetics 60-1 and like I said, once the engine is wound-up past 5000rpm, hold on because the car always tries to get loose and is just a wicked ride. All of this done on the stock engine with the colt cams and average boost is 17psi daily.

As for the dual ballbearing 60-1, I didn't have that turbo long as it was an $1100 experimental piece that does not get my approval for the CA18DET for everday use. I set boost at 28psi, pointed the car north on the florida turnpike right next to the dolphin stadium and gave my car the business. I can honestly say that the CA is a boost-loving engine that loves to hang-out in the high rpm ranges. I would run this much boost for over 20 miles (on and off the pedal) which told me that the engine is up to the task, the turbocharger is more designed for the bigger engines or bigger desires.

what was the peak torque like ?

Much more noticeable with the bigger turbos.

I recall u posted punishing a CA18 street S13? @ 30psi... was this the car ?

That car was overboosted180's car and it was three of us in his car just beating the piss out of his engine on pump gas, but with no ill-effects.

30 on pump gas, or do u dial it back a bit for the street ? or use water/meth/alch inj ?

I don't jump back and forth between programs because I found a happy medium with this motor. At the most I'll do with C16 is in crease timing a bit and just feed the thing air and fuel and pull timing at the appropriate rpm.

Just curious about the various paths folk take, and trying to define some limit of components.Obviously you're on top of your tuning game

I try dude, but I am trying to do a bit better. I am on the 40+psi kick now, so some of my thinking will have to be modified a bit for the task at hand. 300whp is a walk-in-the park to obtain, but if people don't have the money or would rather go through the headaches of achieving this feat, they can have the wrenching. And bTW folks, 300whp in an S13 is nothing to sneeze at. Try 400+whp in a nissan sentra; now that's something to sneeze at.

dee

[dash]

thanks for the reply. Impressive indeed. Good stuff!Nice to see what a composite head gasket & oe pistons can stand up to on a well tuned CA18

[sjbsuperman1425]

my friend and I were pondering something when we removed my head gasket last night.. why is it that there are only water jackets in the rear of the head gasket and not all the way around to the other cylinders? the jackets are in the head, and the block IIRC? just curious is all.

[r34 gtr]

UUUuuuuhhh... good question?

Well, there are coolant passages between the other cylinders, just not big ones like at the back of the engine.

[float_6969]

It's to direct the coolant flow. The coolant is going to take the path of least resistance, so if you don't have the front 3 ports partially blocked off, when the coolant comes out of the radiator and into the water jacket by the 1st cylinder, it'll just go straight up into the head and back out to the thermostat housing, never cooling the other 3 cylinders or combustion chambers.

[sjbsuperman1425]

that makes since. thats probably something I should've known but thanks for clearing it up for me.

[r34 gtr]

YAY!!!