Copper "head gaskets" on a new build?

[TouringBubble]

I'm pretty new to building ACVW stuff and I've heard arguments both for and against copper "head gaskets." Does it really matter either way with new parts? I've seen some suggesting to use the .040" or .060" copper shim and set the deck height to 0. I'm just hoping for a little direction ... searched for a discussion and couldn't find much.

This is my build ...

76mm crank
5.5" rods
94mm B pistons (read here that this combos results in close to an .060" deck with no shims, which is my target)
New CB mini wedgeport heads, flycut to 55cc
9:1 compression
EFI w/ Megasquirt

Suggestions? Copper gasket or no?

Thanks for any help.

[David Miskov]

If you already have .060 deck, why would you use a copper gasket?

[TouringBubble]

I have not yet assembled the motor, so I don't know what the exact deck height will be with no shims. Trying to gauge if I should plan to run the gasket or not, which may change my plans. The case is decked and the heads are being ported and flycut right now ... other than that, the build is open. what I posted are the specs I have worked out and an estimated deck height.

[David Miskov]

Of course you have to mock up everything and see what the actual deck is but if it's close to .060 I would say no copper gasket.

[TouringBubble]

Thanks David. I figured that with new parts it should be close to a machine fit and I'd have no compression issues.

[Marc]

IF all dimensions come up "nominal" you can expect to need ~.020" cylinder base shims to end up with .050" piston deck (the least I'd run on a longevity engine with 94s).
But that is a mighty big IF, so you'll not know until mockup - the biggest single variable will be the point at which they stop decking the case after opening it up for the 94s. If they leave you with more than .060" you'll probably want to go back for more decking (or have the barrels shortened a little). With 55cc chambers and .050-.060" deck your C.R. will be between 9 and 9¼:1.
There's no difference in the quench effect for a given piston-to-head clearance (doesn't matter what part of it, if any, is due to a head gasket) and IMO a head gasket is just one more place for something to go wrong. I can see using them as a "fuse" on a turbo motor - if one blows and you recognize the problem and shut down immediately it could save having to do any restorative machinework. They're also good for making C.R. and/or displacement changes on a drag engine that's campaigned at vastly different altitudes...but 99% of the time you'll be better off with direct contact beween cylinders and heads.

[TouringBubble]

Thank you for that informative post Marc.

So, with those specs, I can expect to need a .020" shim at the base. The deck looks pretty "flat" to me. Not knowing VW cases, the deck looks just a touch below the original flat face of the case, where they were raised a good 1.5mm before the decking.

This is not a longevity motor. It will not be streeted often. It's being build specifically for rallycross events. I was looking for a C:R between 9 and 9.5, so it looks like my choices were close according to your reply.

No big altitude changes planned here. Maybe a few hundred feet at most.

Thanks again for the great info.

[Marc]

Because it's necessary to machine off the entire raised rim around the cylinder opening to establish a wide enough flat seating surface for 94 barrels, they're made a little longer than smaller bores. Just how much decking is needed varies with the individual case casting; if they didn't have to go below flush with the surrounding surface you may end up with the desired piston deck without any shims. You could get away with a slightly tighter deck I suppose, but I still wouldn't go below .045".
76mm, "B" pistons, and 5.5" rods makes a neat package most of the time.

[craigvwdude]

I have tore apart two different engines that used copper head gaskets. (none that I built) On both motors the copper gaskets were "sucked" in. One was a type 1 and the other a type 4.
On one of them, part of the copper broke off and got wrapped around the valve and hung it open.
I wouldn't use copper head gaskets if I had too..
Use cylnder shims to adjust deck.

[Bruce2]

... the copper gaskets were "sucked" in. One was a type 1 and the other a type 4.
On one of them, part of the copper broke off and got wrapped around the valve and hung it open.

"Parts left out cost nothing and cause no service problems"

I'll never use them.

They attempt to solve a problem that doesn't exist.

[TouringBubble]

Thanks for the info guys. Marc, here is an image that might show the case deck work ...

Pic of case work

[Marc]

They definitely didn't take off any more than the minimum - one wonders if this is the first time they've ever cut a case for 94s. You may end up with enough (if not too much) piston deck without any shims.
I'm also concerned about how uneven the cut on #3 is. It could be that's just what the casting of your case required, but you'd better plug some barrels in and put a straightedge across the tops to make sure they're level (always a good idea anyway).

http://www.geneberg.com/cat.php?cPath=1_30

It depends upon the case but you can often get away without this at the 90.5/92 diameter - but it's a must with 94s, which is why 94 cylinders are 114mm long, compared to 112.5mm for smaller bores - it's anticipated that the case will be decked all around about the way yours looks on the forward side of #3. When this is done with the headstud inserts in place, they all end up getting nicked like your front-bottom #3. If they stand proud above the case you may have trouble with them interfering with the cylinders.

[TouringBubble]

All of the stud inserts are stepped from the deck work and the parts toward the bores are flush with the case face. The work was done by Steve Sands at Pro-Flow Performance. He came highly recommended and I'm certain that he's cut lots of heads for 94s. I will look at the uneven cut on #3 when I get home ... I didn't notice until I looked at the photo today. I assume, as you mentioned, that the case had a slight rise there. I will definitely check the barrels before assembly. Thanks again.

[Marc]

This is what a case typically looks like when "properly" cut for 94s:




This isn't just my personal opinion.

http://www.msgulfcoastvwclub.org/TechPages/Tech6.html
"When cutting a case for late 90.5 or 92mm cylinders there's very little left of the ledge that the cylinder must seat on. It depends upon the individual casting, but in many cases (pun intended) you need to "deck" the seating surface clear down to the side of the block to establish a flat area of sufficient width...this absolutely MUST be done in all cases with 94mm cylinders, and their "out-of-the-box" deck height takes that into account."

[TouringBubble]

Well, that's upsetting, but thank you for the info. When I get home I will look over the case with this new info in mind. I suppose there is a chance that he decked only the absolute minimum required for a flat mating surface. But, being a machine fit setup, I can see exactly why I'd want to have the deck milled as shown in your example.