For my first rebuild (318) I used Aviation on the cork gaskets. No leaks for the 10 years I kept it but lets the gasket squeeze out some…
When I got a 265 hemi, the rocker cover leaked. Spoke to guy at work who used to work in a Chrysler Dealership. He just smiled and said do what the factory did and use the cork gasket without any sealer. Did that and worked fine. Just had to tweak the bolts over the years as the cork compresses.
Mustang 289 we bought had leaks in rocker covers. Decided to try the latest rubber gasket alternative. Failed! Bought standard cork and stopped the leaks without sealer. Think the head casting is a bit rough for the rubber.
Just my experience. I’m sticking to factory type gaskets without sealer unless the factory calls for it (eg intake manifold corners). Any fans of “Nick’s Garage” will know this is his advice is for a leak free engine (and he has done a few of them!). “Uncle Tony” also once mentioned for gaskets on parts often removed, put baby powder on one side and it will seal but won’t stick, letting you reuse the gasket.
Cheers
From: chrysler-300-club-international@xxxxxxxxxxxxxxxx <chrysler-300-club-international@xxxxxxxxxxxxxxxx> On Behalf Of John Grady
Sent: Saturday, 9 August 2025 6:41 AM
To: dave mason <forwardlook300@xxxxxxxxx>
Cc: club chrysler <chrysler-300-club-international@xxxxxxxxxxxxxxxx>
Subject: Re: {Chrysler 300} Re: Gasket maker. Yes or no?
i noticed the comment about difficult removal if cork is glued to valve cover . ( or head) That is right — if you use weatherstrip cement or any kind of adhesive . But there are places for that . See later in this . Old style Permatex, Aviation etc kind of a loser now. Impossible to get off anything ( like fingers) And seems not to work well
However— if you use rtv it will all peel clean right off the metal , a good and bad thing . I think it is only good the first time ( and it is!) to attach to cover , thin dont let it show .
But: READ the directions. Follow exactly
Not attaching gaskets in spots to valve cover somehow can lead to frustration , it can fall inwards but if all is otherwise good , re: positioning it and flat cover gasket works ok dry with cork . A dot of ws holds it, in cover corners etc till assembled maybe any where it fights you , sometimes along the straight part ,,-and WS is instant dry . Tiny dot like 1/8”
But if a dim bulb overtightened it , ( lots of those) it gets dimples at bolts , probably why 6 bolts later .Will never seal if deformed to inward cone at bolts Follow torque spec , not more
You can fix that deformation with ball peen hammer and flat plate or anvil, metal bar etc . Oil pan too ,and Chevy guys have little wing shaped washers to spread out clamp force
On Rtv , lots of variants now beyond red and blue .
Permatex copper is great stuff , worth $ — 800F — it says its ok on exhaust at head . So why buy red or blue? I like how it spreads and works , my go to now.
Then by accident I found the grey Permatex stuff that is 100% gasoline resistant . On 57-59 gas tank filler and some later ( dodge dart ) it is a god send . You no longer need to attempt ( right word) to change that impossible O ring , hard as a rock , where filler pipe joins tank , why your 300 smells like gas .
Put a bead of this on old male part , leave the old O ring slide it in , it seals like bulletproof , you have time to bolt all down
Good on carb bowls below gas line if a drip too , and the gauge cap at tank if fighting you
“ Better things through Chemistry” etc
The valve cover fight of all time is the zig zag ones on Poly head especially Dodge 325 . Lower part of the zig zag gasket path , just over exhaust manifold is below the standing oil line , sitting right at that seam , inside the cover , engine off . So it leaks sitting engine off , for a year .
Where the above sequence of dots to keep alignment in the cover and an RTV bead to head first came to be , !!
RTV only on lower side , (of head casting ) put on the head or gasket face ( later at any wet spots ) Check cover is flat , had to add washers at the clamp bolts too . And yes smooth casting face — no casting divots ( watch for that on master cyl too)
3 rd time the charm , no leaks at zig zag
last , fir any thing you torque or remove later into oil or water, nothing bests Rectorseal. ? some kind of fine clay in oil , made for steam gas etc pipe threads . Love the stuff , head bolts studs etc — since 1920’s .Never ever white teflon tape . Amateur time
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