Hylomar vs Permatex High Tack on my head gasket pushrod tunnels

I have a new tube of Hylomar and a bottle of Permatex High Tack.
I have used Permatex Aviation Form A Gasket in the past but never Hylomar.

So I just put samples of both of them on a piece of metal to compare. A thin layer of each and then a thick blob of each.

The Permatex dries to not being tacky but stays very elastic, like that paper rubber cement that we used to play with in high school. It sets like a rubber band film that can stretch.

The Hylomar is pretty dry to the touch but if pressed or pulled apart it is a little sticky. It is still in a state where it still flows if pressed.

Both are rated to 500 degrees.

Which would you use if these were your only choices???!!!!

Thanks
Dennis

Not that I'm an expert but I think these are both fairly suitable but I would note that I like hylomar AF better than regular hylomar.

I am also no expert and have never used Permatex. However, I have been using Hylomar blue to seal the pushrod tunnels on both my 650SS and 850 Commado. Works great! Currently running a copper head gasket on the 650SS, composite on the 850 Commando

Thanks Britstuff,

Do you put the Hylomar all the way around the pushrod tunnels (ie back of bike side), or just at the front where they could leak out onto the cylinders?

Do you put a very, very little around the oil drain passage hole in the gasket.

Thanks
Dennis

Just sparingly to the front, to stop exterior oil leaks.

Never had a problem with the drain hole, (assuming you mean the small one towards the rear and to the right that goes through the head gasket). Also using sealant around the hole would worry me as of course the sealant could block the hole.

The base of the two studs at the front of the barrels can sometimes intrude into the pushrod tunnels, allowing oil to migrate up the studs. I install the studs with some blue loctite which seems to work as an effective seal.

Also, I should have mentioned, I just realized I did use permatex copper gasket spray to spray the copper head gasket on my 650ss and a bit of Hylomar blue as described above.

Sorry for any confusion caused.

DennisMo said:

Thanks Britstuff,

Do you put the Hylomar all the way around the pushrod tunnels (ie back of bike side), or just at the front where they could leak out onto the cylinders?

Do you put a very, very little around the oil drain passage hole in the gasket.

Thanks
Dennis

Click to expand...

If you’re gonna use sealant then put it around the whole hole. You can’t seal half a hole…

Do you believe in Sods Law? If so, put around the drain hole too.

This is a great video on the use of Hylomar. If you use this method you can make sure you havn’t blocked any passageways before final assembly.

neither

read below

(add a loop of fine .005" copper wire around the tunnels)

HEAD GASKET SEALER COMPARISON


Pliobond darkens & hardens at 450 to 500F and loses integrity at 500 but still stays in place and when its cooled it remains adhered to the metal. Stays adhered long term at 400 F.



JB epoxy weld good to 450 and still stays in place at 500 but loses adhesion.



Permatex copper “spray a gasket” high temp – starts smoking and loses adhesion at 400 F but stays in place and remains adhered when cooled.



K&W “Copper coat” brush on gasket sealer – loses adhesion at 400 F but stays in place and is still adhered when cooled.



Silicone sealer resists heat up to 500F, starts to fail by 550 and loses its adhesion. Did not harden but has mediocre oil resistance. Silicone leaks oil as a head gasket sealer.



Permatex “Ultra” silicone based oil resistant gasket maker loses adhesion at approx 500F and fails. Minimal hardening. Silicone leaks oil as a head gasket sealer.



“The right stuff” by permatex should have worked but failed in a Norton as a head gasket sealer.



Hylomar AF stays gooey – non-hardening and no adhesion but good to 500 deg. Aerograde Hylomar is semi hardening and has some adhesion (but not much) after drying and is good to about 450 but looses adhesion around 500 and has poor adhesion compared to pliobond at all temps (worse at 500 deg - loses all adhesion permanently).



Wellseal stays gooey – non hardening and has no adhesion, starts smoking at 400 and turns to water consistency at 450F



Gasgacinch Weldwood and Barge contact cements burned black & hardened before pliobond and lose their adhesion at lower temps around 400F.



Permatex motoseal 1 grey (same as popular Yamabond 4) bubbled at 400F and hardened but did not lose its adhesion. Became very brittle but was still adhered when cool.



Yamabond 5 (clear contact cement) bubbled at 400F burned black, became brittle and lost adhesion.



Permatex high tac turns to liquid, smokes and loses adhesion at about 350 F.



Silver paint gets soft and loses adhesion around 350F



Permatex formagasket 1B starts smoking & bubbles and fails at 250 – 300F.

Thanks Cliff, Britstuff and Jim. I mean it as I am learning.

I have not used copper wire before and it does sounds like the best way but I think I will stick go with Hylomar as it has worked for others and my job will be not overheat the Hylomar!

The oil drain hole in the composite head gasket is right up against the metal fire ring so I can't seal all the way around it, but just to the fire ring.
For the oil drain hole I will likely put a small smear of Hylomar on both sides of gasket in an incomplete circle about 2 mm away from the hole so that squeezed sealant does not spread into the hole, but into the 2 mm area. The video Cliff posted was useful and I will apply the hylomar and press the gasket hard against the metal face by hand to compress it and force it to ooze into my 2mm gap and get closer to the oil hole. I can scrape away any that gets too close. Does this sound ok?

Thanks to another Forum thread I have thought a lot about torquing various fasteners. So I have decided that my 1975 Sears Craftsman click type wrench (collectors item!) which I do recalibrate on a regular basis, should not be trusted as I do not want to pull this engine apart again! I have borrowed a new German made click type wrench from a friend. My Craftsman Torque Wrench is a beauty and I hope that someday some young mechanic or collector (not sure of this is collectable) shows interest in it for a zero price! I even put the melted lead back over the calibrating nut after calibrating!

I probably have three weeks before I torque the head fasteners. In another thread I have been in talks about retorquing the head. At the end of that thread I said that the message to me (first time I have pulled and air-cooled engine apart) is that the head/cylinders cannot seem to withstand the specified torque (over time I guess) thus retorquing can lead to compromise (say like the cylinder deck pulled up around the deck fastener thread hole.)
I have noticed that the thru bolts from my cylinder head to cylinders have slightly impressed their bolt washer patterns in the head. To me, that is one of the many reasons to retorque. As is composite gasket crush.

The machine shop has decked my cylinders as there was a slight pulling up of the deck around the threaded holes. But I see this as having occurred over the 50 years of engine life so that's not too bad or unusual.

So I am thinking to oil the head fastener threads (engine oil unless you suggest something else), with two head fastener torques at least a day or two apart before startup. Maybe even overtorque the first one by two ft lbs.

Then some heat/cool cycles and the question is retorque with loosening the fasteners or not and how many time retorque.
Maybe a combination of retorques without loosening and only one or two retorques with loosening.

Any suggestions you have are very welcome.

Dennis