Exhaust manifold gasket???

[phasmiddy]

I have a cracked exhaust manifold for my 62 Falcon wagon. I bought a new one and all over the box are big green stickers that say "DO NOT USE GASKET ON MANIFOLDS" (what? why?)
But, I also have a new gasket for it. So, I'm unsure whether to use the gasket or not, and I can't find anything online about it on this car specifically, nor have I gotten an answer from the parts company I bought it from. I have found conflicting answers on other car forums.

Thoughts? aaaand-- go!

Michelle

[Jeff W]

In theory, if you had both surfaces freshly milled, you could probably get away installing without a gasket.

I have always used a store bought gasket without problems. Roger (our Pres) makes his own out of sheet copper.

I would use a gasket, torque to specs, and you will be fine.

On the manifold to pipe connection, I can't remember what year they changed from the lower flat gasket to the doughnut type. I thought it was mid year 1962. Be sure to check that compatibility before you start. Get your eye on it rather than just going by the year range in your parts catalog. If anyone has done exhaust work in the last 50 years, they likely upgraded to the doughnut type.

I should add... torque again after a few weeks of driving. I check mine every season because I haven't installed the fancy lock washers now available.

[phasmiddy]

Thanks so much for the info. The stickers on the box really threw me.. why would they say not to use a gasket? Is there a certain model that this manifold can go on that shouldn't have a gasket? I will be using the gasket. Haha.

[Luva65wagon]

I looked that up before and it's sort of like this:

From the factory, with nice machined surfaces (new head/new manifold), the exhaust manifold would seal very well with no gasket. They used either a special silicon grease, or nothing. The benefit here, in an area prone to seeing hot/cold cycles, was less maintenance.

Gaskets compress with time and you really need to tighten them a few times over the first few weeks to stop the bolts from loosening. Really, it wasn't that they were loosening, it was the gasket shrinking and taking a new 'set.' Failure to re-torque exhaust bolts, with gaskets, causes a lot of failure. No gaskets meant less or no re-tightening. Made everyone happy from the manufacturer to the dealer to the customer.

Of course, that was great when everything was new. The first time you unbolt that manifold from the head it would relax and show it wasn't quite as flat as it once used to be. Now, to get it to seal again, everything would need to be machined flat again. It was that or use a gasket. I think everyone chooses using the gasket.

Care should be taken to tighten them correctly - from the center towards the ends. If it is not perfectly flat and you tighten the ends first; when you then tighten the middle bolts you would be trying to force the ends of the manifold outward against the resistance of the tightened bolts. Not a good thing.

So why the warning to you? Maybe because most people never remember to check their exhaust or header bolts. The gaskets fail pretty quickly if not kept under compression and start eating away the gaskets first and then the manifold or head surfaces. Exhaust gases can be as bad as a cutting torch. They probably will not warranty the manifold for this type of failure. Also, gaskets will allow the manifold to move and flex more. More potential to warp.

Because you have old head and new manifold, use a gasket and remember to check the tightness of the bolts (when cold) about once a week until the gasket stops compressing.

Also, use anti-seize on the bolts to keep them from locking up over time.

[phasmiddy]

You're awesome. Thanks so much for all the advice. :)

[redfalken]

I've always added a thin layer of Permatex Ultra Copper on the engine side of the gasket when I put on a manifold, engine in place. There's usually some pitting and I always feel better about it sealing properly. Not needed for new or machined surfaces.

[Luva65wagon]

I've always added a thin layer of Permatex Ultra Copper...

That's the stuff most I found said they used with no gaskets (and new parts). I suppose it would be good security on gasketed installations then. I will have to get me some and try that next time I do one of these.