Head Gasket: sealant or dry?

[Bryan Boyle]

Getting two schools of thought on whether or not you put some sort (Hylomar or ?) on the head gasket when you fit it. 

Wilkins' book says either way (depending on availability in the shop at the time, I guess...).  I can see why you would, and understand why you wouldn't.  So, I guess the question is, what does the collective think?  Just planning ahead here for my working on it over the winter...FWIW, didn't use any on the R16 when I replaced a leaking gasket back in '08 and it worked out ok...but, given the propensity for the twink to leak, figuring an additional thin coating of something to help in sealing the mating surfaces to the metal bits is not necessarily (and I mean THIN) a deal killer.

So...experiences or ?  Serious question, not meant to cause issues or aspersions. 

[BDA]

You are most likely to get a Cometic head gasket which does not require any sealant. As I understand it, the heat releases something in the gasket that creates the final seal. The thing you may have to decide is which thickness since they come in many different thicknesses. I think 0.040" is sort of a vanilla thickness.

[EuropaTC]

The first time I did a head replacement I was given a jar with some brown gooey substance called "Wellseal" by Chris Foulds, a local specialist at the time. IIRC this was the official line on a supplementary sealant and as I'd never heard of it before, I just followed the advice. I later bought Wilkin's book when it came out and remember he said "Wellseal or dry, nothing else" (or something like that)

Since then I've done the job a few times on both the Elan & Europa and, allowing for a failing memory, I think the last couple of times I fitted the gasket dry. Like BDA I seem to remember reading something about the varnish on the gaskets melting and helping to seal. Although once it's torqued up/compressed I'm not sure it would add a lot.

Brian

[BDA]

I should add that when I put the head back on my engine after an exciting episode in setting valve clearances (if that piques your interest you can read all about it here: http://www.lotuseuropa.org/LotusForum/index.php?topic=768.msg42411#msg42411) I used a dry Cometic head gasket as recommended by Ken at DBE and I’ve had no problems for two years.

[Dilkris]

An interesting topic this and this is an area that I spent a lot of time over during my engine rebuild  - to answer your question after web searching, I didn't use any secondary sealant on my COMETIC head gasket as Quote: "The Cometic MLS gasket is comprised of three to five layers of stainless steel. The outer layers of the gasket are embossed and coated on both sides with a Viton rubber material designed to meet the demands of a variety of harsh sealing environments - but i also have not started my engine yet. 
Cometic gaskets, (in the UK anyway), for the twin cam are available in many thicknesses up to 0.120" and differing bore sizes to compensate for the effects of over enthusiastic head skimming and rebore work. I went for 0.070" as I wanted to return to standard head thickness and compression ratio but be careful here.... if you do use a COMETIC gasket they have small rivets which hold the laminates together and when trial fitting I noticed that one of these rivets sat between the block and the head face; I could have very easily missed this...  I carefully removed it.
Now to what I found the really interesting bit - the twin cam engine really has two head gaskets - the main head gasket and then the cork gasket between the head and timing/water pump cover - and I personally believe ("personal" I say so please you engine wizards on the forum please don't shoot me... ) - that this area is commonly overlooked during engine rebuilds and is the cause of many oil leaks.
The effectiveness of a cork gasket to seal (I am told) is when it is compressed by just 1/3 of its original thickness and I was equally advised by one of those wonderful retired and 80 year old engine builders that are still around that overtightening a cork gasket can cause leaks, as can a cork gasket that is not compressed enough.
With this info in mind - I measured my cork gasket, plus the head to timing cover/water pump face gap and made up filler gaskets from gasket paper accordingly - note: I did use sealant on these.
I believe you can buy these cork gaskets in differing thicknesses - but I could never find out where.
Hope the above helps - please note and I stress "this is what I did....."
Good luck with your build.                             

[BDA]

Over tightening a cork gasket can cause leaks. This is certainly true of the oil pan gasket, those bolts should be torqued to something like six ft-lbs. I’m not familiar with the gasket for the timing cover but I would say that the thinner the cork gasket, the lighter the torque and the more care you should use.

[Dilkris]

Over tightening a cork gasket can cause leaks. This is certainly true of the oil pan gasket, those bolts should be torqued to something like six ft-lbs. I’m not familiar with the gasket for the timing cover but I would say that the thinner the cork gasket, the lighter the torque and the more care you should use.

Hi BDA - long time!!
I agree entirely - the cork gasket for the timing cover on the twin cam is effectively torqued by the head bolts.... I therefore believe the thickness of it upon assembly is critical. 

[Dilkris]

As with many areas of the Lotus Twin Cam Engine - it is actually an engineering nightmare. 

[Bryan Boyle]

As with many areas of the Lotus Twin Cam Engine - it is actually an engineering nightmare. 

I'm pretty certain ACBC and Harry Mundy did not expect anyone to be talking about keeping these mills running 50+ years after the fact and designed them to last about as long as anything else did back then. 

That they still are, in various stages of repair, is a testament to the initial design and construction, IMHO.

[Dilkris]

I'm pretty certain ACBC and Harry Mundy did not expect anyone to be talking about keeping these mills running 50+ years after the fact and designed them to last about as long as anything else did back then.

Mmm .......there are many automotive engineering masterpieces in existence, still running today, which were designed in excess of 50 years ago, but as regards being up there for technical questionability, the twin cam surely has to be close to the top.