gaskets

[tahoe healey]

Seems we have a lull in postings so I'll start some controversy. When using paper gaskets some have suggested adding silicon or light layer of gasket maker. Others have said to leave it dry. Who has an opinion?

 

[John Loftus]

It must be slow around here because Henri is on vacation

My favorite is Hylomar HPF gasket dressing(sold by Permatex now). Spread thin on both sides of the gasket and on the mating surfaces it accomplishes a few things: It holds the gasket in position for assembly. It is extremely effective at preventing oil leaks. And it never hardens which means you can take things apart and the gasket can be reused.

I understand that is was originally developed by Rolls Royce for jet turbine engines.

Here's a few links with more specifics and info on various grades of Hylomar:
https://www.igscorp.com/hylomar.htm
https://www.idc-ltd.co.uk/IDC%20-%20Hylomar%20gasketing.html

Cheers, John

[ 04-17-2003: Message edited by: John Loftus ]

[ 04-17-2003: Message edited by: John Loftus ]</p>

 

[Larry Kronemeyer]

tahoehealey: It really depends on the placement of the gasket. Usually paper gaskets get a coat of Indian Head sealer, but silicone thinly applied very thinly around the bolts, but, then you would use Loctite. Being a certified Mech. I suggest following the recommended sealers the manufacturer suggests, they know how long they will last. Use it like you did not pay for it, but don't let ruin the appearance.
Larry

 

[RF Thom]

Silicone sealer is not always the best, because it has good elongation properties but low shear strength. Rule of thumb is - greater than 0.010 inches - Silicone or RTV [room temperature vulcanizing] sealer, under 0.010 - anerobic sealer [Locktite, Permabond, etc] and again check their product information guidelines. I like to utilize Locktite PST sealer # 567. The PST stands for Pipe Sealant w/ Teflon. It's like plumber sealing tape but in liquid form. This material works great especially on the banjo fittings around SU carbs - stops the weeping period. It coure in the absense of air so it won't set up till the joint is secure, and the excess can be cleaned off with a paper towel. Remember with gaskets you want them tight enough to seal but not to tight to stop thermo expansion, as this will put the gasket mateial into shear breaking the compound and resulting in a leak. Always follow the manufacturers torque recomendations. This is why silicone works so good on 0.020 gap joints, its elongation properties allow it to move with the components. Also buy an acid cure RTV as the acid tends to etch the surfaces enhancing adheason, and remember the better it adhears the better it seals. Also application is critical - put the sealer inside the joint and with torquing squeeze out the excess. You'll never force the material into a 0.010 joint gap.

Regards, Bob

 

[Dave Russell]

John,

I agree with you on the Hylomar HPF. As far as I am concerned, it is far superior to the silicone compounds. I especially like the fact that it will bond through light oil films, a factor when reusing old gaskets.
D

[ 04-18-2003: Message edited by: Dave Russell ]</p>

 

[tahoe healey]

Okay, so no controversy. All seem to agree. Then why do we use "paper" gaskets? This is interesting to me so I want to thank all who have responded.

 

[RF Thom]

Paper gaskets are used because no surface can be machined completely smooth, thus it will weep fluids. The paper etc materials allow for some conformance between the surfaces. You can assemble using the new silicone / anaerobic sealers which were deveploped after 1970, but remember that the paper etc gasket thickness is part of the joint limit stack, and eliminating them should be carefully considered first. For ezample - bolts may bottom out and thus not apply any clamp load to the joint, or bearing end clearances may be reduce to eliminate engineered in oil film consideations, etc.
So keep using the gaskets but enhance them with the new modern sealers.

Regards, Bob

 

[tahoe healey]

thank you for your great answer. I'd not considered the thickness factor. Always learning things on this forum.

 

[Ken G]

I might add a bit of experience on thickness. I had a lot of play in the steering of my Rover, and the adjustment, involving slackening bolts holding on the top of the steering box and hammering it sideways slightly, was at its limit. For other reasons, I dismantled the box, to find that the last person had assembled it with blue goop (RTV). I added a fiber gasket i.e. a little extra thickness, and behold, the adjustment now covers the correct range.

Ken G, 1925 Rover 16/50 (San Francisco)

 

[John Loftus]

<blockquote><font size="1" face="Verdana, Arial">quote:</font><hr>Originally posted by Ken G:
I added a fiber gasket i.e. a little extra thickness, and behold, the adjustment now covers the correct range.<hr></blockquote>

Yup. On the AH steering idler there is a paper gasket under the idler top cap. The manual points out that you adjust the idler shaft end-float by the number of gaskets. When I rebuilt mine it took two gaskets to get rid of the end-float while still being able to turn the shaft freely when the top cap screw were fully tightened. Eliminate the gaskets there would be no turning at all.

Cheers, John