BC

Have you used the "copper spray" in your installations and if you have what was the outcome?

Have you used no spray at all but got to the "very smooth" 50 ra rating of the head and block surfaces and had no issue? Did you scuff the surface and let it slide with no problems?

Many people have had some slight 'Seepage' issues when installing these MLS head gaskets, some temporary and some long term. There was a bossing (the pressing of the metal core of the gasket with outward dents to mate properly with the head and block surfaces) about 8 months ago, so has anyone experienced installations SINCE then?

I will be using ARP head studs, so I will be calling ARP to ask what the think I should do in the way of re-torquing after an initial warm up.

I want to do this right the first time.

Mike Simard

I've used the copper spray and have had good results in other aluminum block applications, I believe it acts as a lubricant and is good practice. A good surface finish is important, I like to Scotchbrite the surface after machining to break any sharp edges that could scrtatch the Viton coating of the gasket.

90 S-4

Don't use the copper spray, race teams in England that use Cometic gaskets have been using
Hylomar spray on sealant. It had to do with the frequentce of the rebuilds. For a motor over
here thats planning on staying together for a long time & in a street/track car, the most important
thing is the surface prep, ask Cometic what their ideal surface prep should be. It's a differant finish
than a standard type head gasket needs. I researched this too and came to the same conclusion
that Todd did. 1. proper surface 2.retorque 3.Hylomar ok but not nessecarry 4. a little silicon
around a few of the troublesome water jacket areas. I was told only a few shops have the right
machine to surface the block deck area, worth it to ship the block to the right place even if its only
getting that done to it. The embossing problems have long since been solved (thanks to Todd) .



http://www.hylomar.co.uk/index.htm

atb

Brendan,

I used the Cometics on the motor I built for the Rear Mount Turbo Car. I believe the gaskets were ordered last summer. I seem to recall that these were the updated versions. They did have embossing around their perimeter.

The block had been nikasiled, so the tops of the cylinder towers and water jacket had the very rough metal etched finish to them. The heads were not faced off, and even though they were steam/jet washed the head surfaces were not bare metal clean.

My personal belief in using any type of contact or sealant material with a gasket of any kind is to make sure all contact surfaces are coated, and that the coated surfaces are properly cured before assembly. Depending on the parts function, I'd like to see the assembled parts dry for awhile before starting up.

I used the copper spray. The cylinder towers and water jackets on the block were masked off. The combustion chambers in the heads were masked off. The head gaskets were hung by wires from the lift arms with the lift at its maximum high position. All surfaces-block, both sides of gasket, and head were coated twice. The first was a tack coat which was thick enough that it went on evenly, but thin enough that you could see the native material underneath. This tack coat was allowed to dry for about 30 minutes. The second coat was applied to provide an even fiinish, and was thick enough that now you could not see the native material underneath and the finish was a solid opaque copper.

This engine used the stock head bolts, and they were step torqued over a two day period, meaning I installed the heads and did the first stage of the head bolt torquing and then came back the next day to do the final step.

The head bolts have not been retorqued, and to the best of my knowledge, there had been no weeping around the gaskets. The motor had been running 5lbs boost, (with 9:1 C/R) and I think was recently ratched up to 7-10lbs. Still holding together. In the recent past I know one of the suppliers of the Cometics has shyed away from recommending them and has suggested that I used the 968 gasket for my stroker motor, but I think properly installed its a good product and still plan on going with them.

Regarding the surface finish. My heads have been faced off, the block has been decked. The decks will be masked off to prevent them from getting etched. So basically I'll be dealing with two very clean machine surfaces on my install. Maybe the rough surface of the turbo motor helped it hold seal?

BC

I had the heads (after a rebuild) RE-surfaced to a very shiny and smooth surface and flattened (they came out of the rebuild with a "tilt" as Todd described), so I am less worried about the heads than I am about the block, which was also surfaced, but at a local machine shop. Its smoother than any other blocks I have seen pics of in this forum, but this car will be spotless, and I would hate to have to deal with leaks.

Which Hylomar would you suggest if it were to be planned for usage?

Where would you have the block surfaced if not at Todd's place?

Which Silicone?

90 S-4

I have the pt # of the spray at home, PAW in chatsworth sells it -- I'll get it later -- sorta working now
Can't recommend a So Cal machine shop . Ask todd the name of the machine that can do it, I think
its " Masak" ?? but check with him then call locally to see if anyone can duplicate the surface your
after. I, like Mike Simard -- have used with good success copper spray. In fact I just finished putting
together a sbc Donovan & used the copper spray on it (so far so good) My choice not to use it on the
928 mtr was more of a compatability issue. The copper is ok but the Hylomar was more advanced.

BC

Thats funny that you have no machine shop to suggest here in SoCal, the empire of cool cars and car people. I feel the same way.

Interesting read:

http://www.engine-builder.com/ar/406HeadBlock.pdf

BC

Thanks!

90 S-4

...

BC

Well there you go.

http://www.hylomar.co.uk/universalblue.htm

GregBBRD

We use 968 gaskets on the 104mm engines. We have been doing this for years. They take quite a bit of modification, in order to work properly....that is the only downside. Mark Anderson has never had any other type of gasket in his engine....and it gets driven pretty hard. Certainly, the "fire" ring of this gasket is more fragile than the Cometic gasket. Detonation will break the "fire" ring in half and cause combustion to go places it is not intended to be. However, this is not all a bad thing. If a 928 engine detonates very much, the stock soft (intended for street use) rod bearings will fail very quickly. Whenever we have had an engine detonate enough to hurt the head gasket, the rod bearings will have always pounded enough to loose their "crush" in the rod. They will spin fairly soon after they get pounded. Failure to address this shows up as a large vent in the side of the block, with hot steel parts laying in the street. I'd rather have to replace a head gasket, personally.

We tried the Cometic thing on several engines. We never tried any "spray" cures, since Cometic didn't seem to think this was needed. We got tired of the "Rainbird" sprinkler effect that the Cometics had. They all leaked, some fairly badly, until the engine was warmed up and cooled down several times. Some quit leaking as badly after all of this, but some still "seap" to this day. BTW, retorquing a head gasket is a pain in the butt on a 928 engine.

We have returned to using 968 gaskets and have given up on the Cometic thing. The 968 gaskets work great and there are no sealing issues to worry about. You don't have to worry about what "magic" spray to use to keep them from leaking. You don't have to fret about how smooth your heads and block are. You do need to control detonation, but you need to control that, anyway.

For what it is worth, we were fairly big into the 944 Turbo market for years. We built many, many of these engines. The Raceware/ARP hardware thing never worked for us either. I literally have boxes full of this stuff that we took out of engines. The stock head studs, with the correct nuts, worked better than anything else. Seems that the stock studs streatched over a bigger dimension and this helped to keep the heads "clamped" onto the block as the boost increased. We use stock head bolts on all our 928 engines. We do buy new ones and don't try reusing the head bolts with 100,000 miles on them. The old bolts don't streatch very consistantly and should be re-used with caution, and certainly should never be reused on a high performance engine. You can keep track of what is happening with the stock bolts by keeping track of how many ft. lbs. it takes to rotate the bolt 90 degrees. Snap-on makes a torque wrench that keeps track of degrees of rotation and ft. lbs. at the same time, which makes this job easier to do.

gb

BC

People will always want to stick with the original stuff, because of the mere fact that it IS the original stuff. But the point is that the OEM Japanese Car manufacturers have been usuing MLS gaskets since the early 90s at least.

The RA of the sealing surfaces need to be, realistically, WAY "smoother" than what is required for the "matrix" type stock head gaskets that are essentially 40 year old technology.

It may be a shock to some, but new things many times DO work, but the proceedures by which they are used must be changed. Hence the article I posted about new and much updated "surfaced Prep" proceedures.

It seems as though that if you can't see yourself and comb your hair in the reflection on the deck surface and the head sealing surface, you need more work on that area to install these things dry.

Its also a point of interest that Honda and Toyota, the main automakers, I believe, that have used these "new fangled" MLS gaskets in thier cars for 17 years now at least, have the same open deck or similar design as we do.

And when I mentioned that I was usuing ARP head studs to the Tech at Cometic with thier gaskets, he said a very quick and somehow relieved sounding "Good!"

Vilhuer

Very interesting info. Next obvious question is how much head and block roughness can remain if Hylomar is used?

Other question is does Cometics have holes for extra cooling holes on GTS head? I have asked this from Cometic directly without geting any reply.

90 S-4

I wish I could have used a oem 968 gasket, but as my bore is 108.9 I had no choice but to go
aftermarket.

Mike Simard

Erkka, here's a set of custom 109mm Cometics, do they have what you need?