Hylomar vs. Yamabond

Morning gents,

Just heading out to grab one or the other to use on the cylinder barrel bottom.
"74 MKII.
I have never used either of these products, and was wondering if you might be able to give me a bit of insight.

Are they like a silicone that can be spread, and let dry a bit before contact?
There is one oilway hole, with about 1/4 " contact surface to the outside, that is my concern.

I remember a thread from about a year ago, with a picture, and someone was using a silk thread.
I don't remember if that was to keep compound out of the hole...or to provide some dimension...or both.

Apprciate your thoughts

Sorry...I should rephrase a bit.

I'm familiar with the discussions on using the thread....just not familiar with the procedure.

does one put a layer of the compound on and then lay the thread in?
Is making the ends meet, a critical factor?

A cylinder base gasket is available now that is not illustrated in the parts book. When I rebuilt the top end of my 74, I used a new gasket plus a thin layer of Wellseal on both sides. I like Wellseal a lot and it is supposed to never harden and also be soluble in oil so that it will not clog oilways. I think Yamabond and Hylomar are pretty equivalent but I have never used them.

The Hylomar uses acetone as a drying agent, so it dries pretty quick and is very strange to work with. I found the best way is to put it on right out of the tube, using the opening where the stuff comes out to spread it around. Brushes don't seem to work, if you put your finger on it, same thing. It apparently doesn't take much. I used in on nearly everything, even the crank flanges. Only leak I have so far was the exhaust rocker covers that I didn't use anything and when I put the Hylomar on them it quit. Never used the silk thread.

Can't speak to yamabond, I've never had any. I thought it was similar to the Ultimate Gray gasket maker, don't get the Ultimate Gray RTV, unless you want RTV.

I'm sure Hobot will have something to say.

Dave
69S

Yamabond is a solvent based sealer. It is not silicone or RTV type. It works very well to seal surfaces where there is no gasket such as case halves if they are close fitting. Don't use it if you are planning on taking it apart regularly as you will think the cases are welded together when you try to pull them apart.

For cylinder bases I like to use a gasket because the surfaces tend to pull apart and break the seal. I use a thin coat of locktite or permatex anaerobic sealer on the gasket to help keep it glued in place. Hylomar will work there also.

I only use RTV to seal windows on my house. It is not very oil proof and tends to come loose inside the motor and plug up things like oil holes. It is also very corrosive to aluminum. Jim

If you are using a gasket and joint faces are good, there is no real need to any sort of compound, simply a smear of grease to hold the gasket in position and put things together. On joints which are damaged, or where no gasket is fitted then Yamabond is to be preferred, as this seems to just about the best available, and there is no chance of it blocking oil ways, which can be a problem with several other products, if too much is applied.

comnoz said:

Yamabond is a solvent based sealer. It is not silicone or RTV type. It works very well to seal surfaces where there is no gasket such as case halves if they are close fitting. Don't use it if you are planning on taking it apart regularly as you will think the cases are welded together when you try to pull them apart.

For cylinder bases I like to use a gasket because the surfaces tend to pull apart and break the seal. I use a thin coat of locktite or permatex anaerobic sealer on the gasket to help keep it glued in place. Hylomar will work there also.

I only use RTV to seal windows on my house. It is not very oil proof and tends to come loose inside the motor and plug up things like oil holes. It is also very corrosive to aluminum. Jim

Click to expand...

What do you think about using an anaerobic without a gasket at the cylinder base? I use Loctite 518 on case halves with excellent results and have considered using it on the cylinder base without a gasket.

Going to be dropping cylinders on a rebuild tomorrow and might do this.

I used Hylomar when I built my TR3 and, like Dave, found it difficult to use. I used Yamabond on my Mk3 build on the split halves and at the bottom of the jugs, and found it really easy to apply. Two years now, and not a drop of oil. Yamabond is a favorite of the Porsche forums as well. I still have a tube of Hylomar at the bottom of my adhesive chest, unused.

Fred Eaton turned me on to Gasgacinch for dressing gaskets. Harley specs it out for their shops. I used it on my Mk3 and Victor builds. Easy to use, but I really don't have enough hours with it to give a critical report. No leaks, though.

What do you think about using an anaerobic without a gasket at the cylinder base? I use Loctite 518 on case halves with excellent results and have considered using it on the cylinder base without a gasket.

Going to be dropping cylinders on a rebuild tomorrow and might do this.[/quote]

I have used locktite 518 without a gasket on the cylinder base many times. I still do this on my racebike motors. However on a streetbike motor I have had trouble with small leaks after several years without a gasket and have gone back to using them. Jim

In old air craft is was standard procedure to lay a cotton or silk thread in the seam to both take up some space and five fiber support to sealer. New synthetic polymer threads I found tend to melt flatter after nip up leaving some space rather that filling in and also can melt and contract and part leaving gap in the coverage.

I'm sold on Hylomar myself having had failures of the other tar like and grey clay like sealers. If ya press Cdo to red line they become elastic so barrel dances on cases both in squirming shear and in lifting gaps. The grey stuff can harden in the compression phase for fractures that weep oil out in the tension/gap phase. Plus the grey and tar like goops act like glue to part pieces and a job to clean off. I have sworn off base plates myself, especially frail crush-able paper.

For larger areas like barrel or head I push out Hylomar into a cap and use 1/2"
short stiff bristle brush to dabble on and spread. Other tools or spreaders or fingers just seem to snag and roll it up or to lift it off with tool-finger removal.

For TS case that need gasket as part of oil pump seal space, I Hylomar gasket on cover and grease the case side so it stays on cover when removed time to time.

Am experimenting with Trixie Combat using copper annealed gasket with Hylomar on both sides as good to 600' F and copper is known to weep about regardless of torque. Start up predicted in a few weeks.

Hylomar was developed by Royals Royce then sold off to others to market.

http://www.hylomarblue.com/Hylomar%20-% ... istory.htm

I like Wellseal,
It's similar to Holomar, as in it's a non drying type sealant, just apply one or two coats with a brush to whatever you want to seal and let it sit for a while before bolting everything up. It's thinner than Holomar which makes it easier to work with and clean off.
For anything that you want to remove once in a while I like high temp grease and a gasket. As for fitting the barrels, I personally would use a gasket and grease or a non hardening sealant.

Webby

Wellseal works very well if joint faces are pretty much perfect, but if this is the case and gaskets are being used there is no real need for anything other than grease anyway. Yamabond has the major advantages of being able to perfectly seal less than perfect joint faces, and not finding its way into oil ways, which is very common with Hylomar, and can result in big problems on modern motors.

Hm, one of Hylomar's main safety features bragged about is that excess bead does not break off to clog passages. Fortunately seam sealing ain't rocket science so many ways work fine. In last version of Ms Peel, only engine or gear box gasket I had left was TS cover, silicon rocker boxes and head gasket and wondering if just Hylomar would elimate the top side ones.

I used Yamahabond on my TZ's years ago, the dogs bollocks now I use a Loctite product (which I can't remember the number of right now) its used by Toyota dealers.
Hylomar is fine but not the best IMHO

Using the paper gasket dry is cheap and easy, no leaks, but buy an extra in case you rip the first. It sucks to wait an extra week for a piece of paper.