Cometic sump gasket question.

[dougal9887]

Having had an annoying leak at the rear of the sump and had trouble previously with cork gaskets squeezing out I have decided to try the Cometic gaskets and trimmed down rubber semi-circle gaskets.
I expected the Cometic gaskets to be the usual foam coated metal type but find that they are a sort of fibrous material. So my question is, are these never the less used without a sealant?
Assuming that to be the case, as I am working from under the car, I propose to keep the gaskets in place by applying a lttle gasket adhesive around three bolt holes each side and use sump bolts and penny washers overnight to stick the gaskets in place. There is a depression formed by the front cover back plate which I think will need a little silicone anyway.
Finally, I assume a smear of silicone should be used on the rubber gaskets and corner joints?
Any comments from experience using this setup would be welcome.
Thanks.
Dougal.

[RichardHawkins]

Dougal,

I bought a cometic sump gasket, and although it is a good fit I found it far too hard. By your description you have something more compliant, which would seem better. Two of my friends buy their sump gaskets from Burton which are described as a cross flow competition sump set or kit. The gasket is fibrous. I could not get a seal with the hard cometic gasket. Having fitted the sump I could still pass a 0.002" feeler through the joint. My car has suffered from a muscular previous owner. Many bolts are stretched, and the sump was bent around every bolt hole. I spent ages straightening the sump, but could not get the cometic to seal.

An American engine building book recommends sticking a cork gasket to one face with sealant, then removing the sump when the sealant has cured, then apply sealant to the sump and refit. He claims this technique reduces the tendency for the cork gasket to spread and split as the bolts are tightened.

Hope this helps

Richard Hawkins

[7skypilot]

Cometic gaskets are used throughout both my Twin Cam and BD engines, including the head gasket.

I reckon they are far superiour to the standard gaskets, especially the cork ones as they do not deform or squeeze out. The steel sandwich head gasket is also reuseable. The Kent gasket set will need the front (or is it the rear?) rubbber gasket trimming - I've done this carefully on a bench grinder, and I apply the tiniest blob of silicone sealant (I generally use Wurth silicone, flange and hydraulic sealants) at the joins. It's worth it to avoid the compression problems associated with cork.

However, as mentioned above, surfaces will need to be pretty true - the Cometic gaskets just don't have the bulk to fill irregular gaps that cork gaskets offer. IIRC the steel head gaskets need to be especially smooth (details are, I think, on the Cometic site). The head also don't need re-torquing after a few miles.

Any sump gasket will be tricky to fit if you're working from under the engine - I've only fitted them when the engine has been on a stand and can be inverted, but your idea of using a minimum amount of silicone to 'stick' the gasket to the block sounds good. And anyway, I can't take the sump off the Elan in situ as it has a standard (ish) chassis.

I also use the Cometic cam cover gasket - but a thin layer of silicone is applied to one surface, and allowed to set with a small weight on the cam cover, before finally 'snugging up' the retaining nuts. This allows easy removal the cam carrier without disturbing the gasket. Yet another great idea I gleaned from this excellent forum.

As testimony to the efficiency of Cometic gaskets, I have rusty sump bolts (or rather rusty cap-heads). The gearbox output seal is another story... but it does ensure that a major part of the chassis is rust-proofed!

Hope this helps.