Headgasket coating question

[suprarich]

That's a good tip on the lock tight!

It will stay a liquid untill you put pressure on with the head bolt install. Then it will turn hard, then really hard after the motor is fired and you get some heat into it. I used to fill casting pinholes in the cast iron cylinder jugs of an older Nitromethane Harley I raced. Then I just used it alone as the headgasket. Held up to that. Has to be 620, it is also called bearing cinch.

 

[bigaaron]

IJ is still here "in spirit", I just sent him this:

I don't know why scientifically speaking, but my 7m recipe still tastes great after a few years of engine builds. If the surfaces on all 7m's were perfect then we would actually be dead and building the engines in heaven.

 

[jdub]

I'm not disagreeing with you that it is not needed, and I appreciate the mutual respect we share.

Thank you...Arron your ability to build a solid 7M is without question. I would not recommend you if I thought otherwise. Being able to machine down to a sub-7 RA spec is amazing And is a testment to your attention to detail.

I think .001 is just not a thick enough viton coating for the 7m in particular. Their recommendations would probably hold true for 99% of the headgaskets they make, but we all know the 7m kinda defies logic on certain levels.

If you know what you are doing...a very thin layer of copper spray will likely not cause a problem...still the manufacturers do not recommend it. My thoughts are against recommending it...especially here. That is due to a 1st time builder getting the "more is better" syndrome...you put very much copper spray on a new MHG and the viton is toast....it will turn into goo and compromise both the viton and the copper.

I honestly believe your success in building a 7M stems from the attention to detail in exceeding the RA spec for the head/block and using the proper torque for the fastner used. MHG's are very picky concerning the surface...they seal because of the smoothness between surfaces. To be honest...with your attention to detail...you could never use copper spray again and get the same results you do now.

Remember that Cometic sells gaskets with rivets in them that will cause a major failure if not removed by the customer. That = poor design in my book. People misinterpreted the 50 RA as meaning the Cometic headgaskets are "more forgiving", yet there have been several blown Cometic MHG's recently because of that misinformation. If they are more forgiving then who needs to surface the deck..... OH No!

Ahhh...the famous rivet. I agree with you...it's a cost saving technique Cometic uses to keep their MHG's together until they are installed. The "forgiving" part is a misnomer...it's only in the sense that the RA is greater than an HKS MHG RA of 30. The RA spec still should be met for the Cometic (or any other MHG for that matter).

And I do like have a good discussion...makes keeping sharp on this stuff a lot more enjoyable :icon_bigg

 

[Nick M]

HKS metal head gaskets are engineered to resist severe levels of heat that are generated by high-horsepower and high-boost applications. All HKS head gaskets are constructed with multiple layers of steel and coated with a special fluorine rubber to provide exceptional sealing. HKS head gaskets are designed to accommodate standard and certain oversized cylinder bores.

For most applications, multiple gasket thicknesses are available to change the dynamic compression ratio for various levels of tuning and engine conditions. (Note: HKS gaskets are not designed to cure sealing problems caused by head or block irregularities.)

I also prefer manufacturers info. It does not say either way, but it does say your engine needs to be prepared ahead of time.

Good info in the thread. Thanks for sharing the experience Aaron.

 

[bigaaron]

Thanks!

Jdub does make some very good points.

Our machine shop has a >$100,000 cbn surfacing machine and they make slow passes taking off very little material at a time.