Revelation Re Those Figure 8 Sleeve Gaskets

[KVH]

I ordered Figure 8 gaskets from Moss. They are steel shim material, or so it appears.

But in my Lower Gasket Set from BPN, those same Figure 8 gaskets are not steel, they are copper.

However, I measured the thickness of the gaskets with a micrometer. The copper ones in my Gasket Set are .0037" thicker than the steel ones, and that is almost exactly the amount of sleeve height clearance recommended above the block.

Why the difference in the gaskets, and doesn't that clearly mean the Moss gaskets are incorrect?

[It's fun being a worrier]

 

[Don Elliott]

IMO, if you have the liners projecting up above the engine block an extra 0.004" and you are planning to use the standard thick copper covered composite gasket that was the original type head gasket, I don't see (IMO) a problem as the new thick and somewhat soft head gasket will compress and you may actually get an even tighter seal between the top of the liner and the head.

The projection height of the liner about the engine block is very critical for those who race or rally a TR where a steel or copper gasket (which is like a piece of shim steel or copper) is used. It has virtually no compressability and therefore the projection height in this case is very critical.

 

[martx-5]

When I took apart my engine, it had copper Fo8s. The ones that I got in my kit were steel. They measured 0.016". I never measured the ones that came out, but the steel ones gave me 0.003"-0.004" height above the block. The steel Fo8s are virtually uncompressible, whereas I assume, that the copper ones would compress a bit. I don't think they would compress quite as much as the difference you are noticing.

The important part is how much the liners protrude when in place. I went through a 'dry run' to measure the heights before everything got gooed up with Wellseal for final assembly. I also remember talking to Ken Gillanders at British Frame & Engine and he mentioned when using the steel Fo8s to run your finger along the gasket on both sides, and you will find one side that has a burr on it. He says that the burr should face towards the block not the liner.

What are the thickness measurements of the two sets of Fo8s that you have??

 

[KVH]

Here are the measurements I have:

Copper: .0205

Steel: .0168 (same as yours)

Difference: .0037

 

[martx-5]

I've read that there are oversize Fo8s available, and I think that the copper ones you have might be those. I would 'dry run' the steel Fo8s and see what kind of readings you get above the deck. You just want the heights to fall within range, and whatever Fo8 does the job is the one to use.

 

[TR3driver]

I just checked a very old (but unused) steel Fo8, and my mic shows it as .0162" Tried to check some others, but they were too rusty to get a good measurement on.

But the reason I've got steel ones left over is because I've always hunted down copper ones to use. The original steel Fo8 gaskets were supposed to be coated with plastic, but the steel replacements don't seem to have the coating.

AFAIK, the only oversize copper ones are made to order by Mordy Dunst, so I doubt you found them in a set.

 

[billspit]

I would call the guys at BPNW and ask them about the difference.

Also, what is the brands of the two Figure 8 seals. The kits sold by BPNW are usually the good ones.

 

[TR3driver]

Stumbled across this just now, while looking for something else. This is a factory service bulletin, dated December 1955. As I read it, the original, original Fo8 gaskets were actually composition (meaning at least partly fibrous material); then were changed to plastic-coated steel sometime before Dec 1955; when they were again changed to copper.

 

[KVH]

What a great piece of history. I figured Wellseal just meant something to seal a well, not Mr. Wellworthy's special formula.

Very interesting quote.