Gaskets
 

In looking at the engine currently in our Lemans (a ‘74 400), I’m seeing a few leaks. Some I can tell why, others I can’t. This is all preliminary but I want to be ready when it warms up to hopefully spend a weekend combing over the car and have it ready to be certified before we can register it for the road.
I’m seeing that the valve covers are leaking oil. Not surprising for an old motor. I was checking out valve cover gaskets and finding that they are available in 1/8” thick and 1/4” thick. Are the 1/4” ones for problematic leaks or does it depend on the engine?
Also, I’m seeing coolant collecting below the intake and valley pan. This requires further diagnosis, but I believe that it’s from the water pump gasket. If not, should I be looking somewhere else for a coolant leak?
Which is a good manufacturer to go with for gaskets? Is RTV recommended with a gasket anywhere in the cooking system? I’ll know more when we fire it up and really let the engine warm up, but I’ll take any pointers on what to look for with these engines.

either valve cover gasket will work, usually the 1/4" ones are used to get a little more clearance for rocker arms.

coolant can definitely be the water pump gasket but it can also be the rubber O ring between the intake & timing cover connection. you can carefully try to retorque the bolts on the water pump & the long bolt for the timing cover to intake. they often work loose & cause or contribute to leaks. try snugging them up but dont over tighten, might stop the leak.

felpro are usually the best gaskets but other brands are fine for these areas too.

i have used a good RTV like permatex ultra black for many years on most gaskets with no problems & it will even help them seal on pitted or uneven surfaces, some on here will say dont use RTV for these areas but permatex says it can be used as a gasket dressing & lots of guys use it without any problems. use a small bead & thin it out with your finger then follow instructions on the tube for curing & final torque. & re torquing after a few heats cycles is a good idea & check them periodically after that.

you will get lots of suggestions on gaskets & sealers & they all will work fine. ultra black is easy to find anywhere & works great for almost any gasket on these engines aside from head & exhaust gaskets that dont usually need sealer.

I used to use RTV black and got a case of the caulk gun tubes of it from my no-deceased father in law who worked for Loctite. Obviously I could not use it all and stored it in the garage. By the time I got around to doing my 455, I grabbed a tube and thought it worked pretty good. That engine ended up leaking like crazy from just about everywhere. I went back and looked at my tube or RTV and noticed it had expired like 5 years ago and had been through probably as many heat/freeze cycles.

So, now I have switched over to RTV grey, keep it in the basement and get a new tube in the cheeze-wiz container every season. The new motor does not leak a drop of oil. https://www.amazon.com/Loctite-5699-...46137685&psc=1

the grey works good too, ive used both black & grey with excellent results.

defenitely cant let them freeze or expire though. & once opened they have a limited shelf life & will harden in the tube but are cheap enough to replace when needed.

RTV Silicone is a gasket MAKER, not a gasket SEALER.

Instructions for use of Ultra Black, direct from Permatex web site:
https://www.permatex.com/products/ga...asket-maker-4/
(click on "Instruction")

Note that there is NO mention of slathering it onto paper/cork/rubber gaskets. It's to be used INSTEAD of a gasket. It is specifically designed to REPLACE gaskets, although "popular (incorrect) use" has led them to list application onto a gasket in the TDS.

There's more than a dozen commercially-available gasket sealers--Gasgacinch, High Tack, Copper Coat, Indian Head, Permatex #1, #2, #3, Hylomar...and others. Any one of them works better than RTV Silicone. There is ZERO reason to misuse RTV Silicone which makes the gasket "slippery" so it squeezes out of position. It's a common mistake to put RTV Silicone onto a gasket, but it's still a mistake.

I'm no fan of Weatherstrip Adhesive as a gasket sealer, either. Works ok, hateful mess to clean-up the next time the assembly comes apart. Weatherstrip Adhesive (Yellow Death) as a gasket dressing/sealer is ANOTHER common mistake...

are you suggesting that permatex was forced to list gasket dressing on the TDS due to popular use? seems a little far fetched, no company would list something if it wasnt an acceptable use for their product.

im not claiming its better than any other product, the OP asked about RTV & i just gave my experience with it. many other reputable pontiac guys use it that way & recommend it for many locations. i was advised to use it by a popular long time pontiac engine builder for the 1/4" cork U gasket for an oil pan that kept leaking with the stock rubber seal.

also you dont slather it on, its a very thin layer, the instruction on the tube says to only go snug & let skin for an hour, then tighten. ive never had a gasket squeeze out from using it.

https://cdn3.evostore.io/documents/f...82180_spec.pdf

Just try a real gasket sealer. First Choice---Gasgacinch. Second Choice--High Tack. Hylomar is--or at least used to be--friggin' amazing, but also wildly expensive. But any of 'em will do.

Try it.

The gasket STICKS instead of slips, and two years from now when you take it apart again, clean-up (except with the Permatex 1, 2, or 3) will be half the problem of RTV silicone.

That's a wealth of information. Thank you. Knowing what to look for is 90 percent of the battle. Our little window of opportunity to go over the car just closed, with a winter blast of 15*F and winds up to 50mph.

I'm assuming that you meant under the intake but on top of the valley pan? If so, your most likely suspect is the mating surface between the water pump and intake, as mentioned above. It's a very common seepage area. I always put a smear of Permatex on that o-ring and those two passage points
at the intake coolant crossover during assembly (Being that the crossover to head mating points are another possible source if water is resting on the valley pan).
If you find the o-rinng to be the culprit, loosen the intake bolts a little before drawing that junction tight on the o-ring, then come back and re-tighten the intake bolts.
Generally speaking, when looking for a leak source, look at the highest wet spot on the engine. The leak will be above that point somewhere....

ive used some of the others mentioned & as i stated they all will work fine... but so does ultra black/grey when used properly as a gasket dressing.

based on the comments above it's not being used properly as a dressing if it was slathered on or there was any slipping of the gasket. or that guy never used it as described if those are his assumed results, but making up false claims about a product is kinda pointless.

use whatever you like, just follow the directions & there should be no issues.

Thanks again, guys. We’re stoked about getting this thing squared away and on the road.

IMHO stay away from cork valve cover gaskets..

I've never had a problem with cork gaskets anywhere myself.
I make a lot of the less complex gaskets for myself from a sheet of cork gasket material. Also have a sheet of paper gasket material. I just made one for my Datsun t-stat housing yesterday. In fact, in a pinch I have made gaskets out of shoe box cardboard for things like that.

X2. My brother and I have done that since the '60's when we couldn't get a store bought gasket.