TheSamba.com :: View topic

Mon Mar 13, 2006 6:51 am

Building a 1904 engine, is it better to use barrel shims or copper head gaskets to get the last 0.040 clearence needed to set the deck height?
Existing deck height is 0.010 and I am aiming at 8.2:1 compression with a total of 0.050 deck height.

Also what is the total maximum height you guys would recommended for barrel shims.

Engine will be for street buggy not off roader or drag car.

thanks

G

Mon Mar 13, 2006 7:41 am

I'd suggest barrel shims when you can. I have been using coppers and there are some drawbacks to using them AFAIAC. I believe that they will crush and cause some loose heads and that the little shelf created by using them is an opportunity for detonation (sharp edges, etc.). Next time I open up my 2332 I am losing them.

Mon Mar 13, 2006 8:20 am

I've used barrel shims only and I've used copperhead and I think they both work well.

Using barrel shims to get zero DH sinks the barrel deeper into the engine case so you may say thats a benefit.

Mharney, in the 2332 scenario you'd want zero DH for your 84 stroke because it gives the piston skirt more area to ride along the cylinder wall.

I haven't experienced any loose studs or leakage of the cylinders using coppers. The convenience of coppers is that in some cases you want to either increase or decrease c/r in a matter of swapping copper gaskets without disrupting silicon seal of the barrel shims and separating piston and cylinder assembly. You can also get custom made gaskets to suite your exact needs.

Mon Mar 13, 2006 7:12 pm

Alan, are you talking about custom made copper head gaskets?
Where? I would love to get some .030 gaskets.

Mon Mar 13, 2006 8:02 pm

1955ccbug wrote: Alan, are you talking about custom made copper head gaskets?
Where? I would love to get some .030 gaskets.

http://www.geersengineering.com/Copper%20Head%20Gaskets.htm

I use the cheapass bugcrap coppers. Shawn Geers gas the quality stuff. I may just go that route next time.

Mon Mar 13, 2006 8:10 pm

Thank you!

Tue Mar 14, 2006 9:14 am

Zero deck is a good recipe for destruction! :)

If all of a sudden the bearings start to go without full failure, you are talking disaster.

Deck height of 0.040 is not that much of a measurement or area gain in cylinder walls.

I have seen motors with zero decks eat ring lands after hitting the head shims.

Zero deck can be done if the machining tolerances are controlled tight so the cylinders do not wander. The "shim" can be machined into the head itself, so you do not have gaskets. BUT the cylinder ID must be smaller than the ledge, or it is disaster waiting to happen.

I would rather do the bottom cylinder shims. Much safer and makes more sense, IMHO.

In this application, however, just install 0.020 shims and you have a nice deck.