Gaskets...

[72bajaben]

So...do you really need the paper gaskets? Or can you use some sort of sealer or RTV or liquid gasket maker?

[raygreenwood]

What part are we taling about?.....it makes a difference. Ray

[72bajaben]

Can you tell which parts matter?

[raygreenwood]

Sorry for the delay.

Virtually every part that HAS a gasket has one for a reason. Gaskets are semi-compressible spacers. They are used to compress into surface irregularities. They also have the ability to keep a range of fluids, vacuum and air pressure from tunneling sideways ...which can happen with RTV's that are used in too thick of a manner, in areas of high vibration, heat and oil.

it also matters the thickness. RTV gasket maker usage in modern cars...show the way those are used to actually "make" gaskets...for example by installing a valve cover at 75% torque....pumping the factory cast or stamped groove...letting it cure..and fully tightening.

Examples where you DONT want to just use RTV in place of gasket paper...in my opinion....are intake to head gasket flange, oil filter to case flange on type 4 and fuel pump to case on type 1 engines.

Places where you CAN get rid of the paper gasket and just use RTV...is on the cylinder to case joint. Keep it thin and even...use One of teh Permatex ultra series....black is best for oil, gray is the stiffest, copper is one of the best all around. All are good to over 500F. Ray

[72bajaben]

Thanks Ray. Im going to bite the bullet and get a gasket kit. This was more of a curiosity question. Is it advisable to use both a paper gasket and RTV?

[Marc]

...Is it advisable to use both a paper gasket and RTV?

Absolutely not! The RTV can soak into the paper, causing it to become "stretchy"...they can actually squish out, causing a loss of head stud tension.

When using used cylinders, there'll be a "ring ridge" at the point of maximum upward travel of the top ring. If they had paper gaskets before, you should use those again to prevent the ring from running into the ridge. Apply a light coat of gasket sealant (just enough to color the paper) ....Permatex spray-on works well here.

The paper gaskets are ~.008" thick, so if you want to go with RTV you need to use either .010" steel cylinder base shims or the stock copper ones for 356 Porsche, which are ~.009" thick, to avoid the ring ridge issue.

[madmike]

If the cylinder has a ridge and it's not just carbon build up it's junks anyhow
hardly anyone uses RTV anymore
Get 'Moto seal' made by locktite/permatex same stuff as Yamabond
about the only place I use paper gaskets are the pump and intakes

[raygreenwood]

Actually more people use RTVs....than ever before....including virtually every OEM. And....Motoseal is technically an RTV by formulation. Good lroduct...but sucks to remove for a valve cover or thin paper gasket formulation.


There are literally thousands of RTV formulations with various types of catalyst systems and properties that far exceed motoseal and Indian head. I am testing one now with a temp range of 1750F comstant.

The problem with RTV is that most people have no idea how to properly select, apply and use them.....and make the assumption that they are all the same except color.

Also....good gaskets are NOT actually paper. The material is actual plant/wood fiber broken down to base cellulose....then chemically treated and encapsulated usually by a polymer adhesive and then pressed into sheets. Oil can over time bleed through the fibers.....but if its a quality vegetable fiber gasket....as they call it....RTV should never soak into it...unless you are starting out with one that is too thin.

Also yamabond and motoseal and indianhead are solvent based. Indianhead is actually alcohol based. You need to be careful what type of gasket the other two are applied to as the solvents can break down the polymers encapsulating the fiber causing the gasket paper to break down. They are both excellent products but have specific uses. Most specifically. ..like Indianhead.....they are perfect for areas that come in contact with fuel....but have lower heat resistance than the better RTVs.

Lots of things to look at. Most people apply RTV to gaskets in a film far too thick fof the durometer of the RTV. Over time. ...vibration and flexing cause the RTV layer to shear apart. Ray