The Cal-look Lounge

Ok all you engine builder guru's. If I don't ask, I won't know.  ;) Running "0" deck, can I run a .040 copper head gasket?? Even maybe .030. Bottom line, what is the minimum I can run? Rods are Eagle 5.5's, 83X94. Thanks guy's!!  ;D

Ted

That depends on how often you want to take it apart and check it.
 ;D. Bottom line you are going to get a bunch of guys that say "yeah run .030" but unless your heads have 65ccs in them .060 will give you 8.5 to 1 or more.  Be safe.

The problem is my pistons have a 10cc dish in them from my previous  setup, and have 57cc in the heads, I hear you Taylor on the compression, but was hoping around 9:1., have .060 and .040 copper head gaskets. Have barrel shims that give me 0 deck or .020 deck. Trying to mix and match for the right setup. I think I can get 8:8 CR, may go with that. Thanks Taylor for your input, your right, don't want to be pulling it apart often.  ::)  ;D

Ted

.040" is the safest minimum when using quality parts. You can always flycut for more! ;D

I have run very little deck before and it is never good for rod bearings.  I like to run all my motors with .050 to .060 now.   That's what I would shoot for.  Like Zach said, flycut them for more.

Taylor, thats interesting. How does higher CR effect the life of rod bearings? More wear due to higher cylinder pressures? My 1914 came out to .060 deck height and 8.3:1 compression without modifications. I was anxious to build the motor, so instead of having the cylinders machined, I ran it. I still wonder how the motor would have run with 9.0:1.

No, what I am saying is that with under .040 deck the piston starts to bang into the head.  Beating up the rod bearings.  Some may say Im wrong.

No, Taylor is right, I heard the samething, from a good source, what happens is that the rods actually stretches at high RPM which cause's the pistons to hit the head if deck is to close. For me, I wanted to know what other engine builders think, wanted to go the limit, but after reading Taylor's reply, I agree, I have some $$$ in this motor, why jeopardize my parts? What I can do is get some undished pistons, problem solved. Good topic, maybe some other builders will chime in with there thoughts.

Ted

i agree with your line of reasoning , ted! but why not get the top surface of the pistons machined? that may decrease the dish CC with a tiny bit, too....

Whenever someone asks about deck height on an internet forum, the instant response is always ".040" — I often wonder how many engines actually end up at that.

When my engine was going together I was inquiring about the deck height and the response from my builder (whom I trust) was that things can get real close when you take piston rock and regular wear-in into consideration. My engine ended up with .060" and 9.5:1

Disclaimer: I'm not an engine builder, but I did stay at a Holiday Inn last night!

parts (crank,rodbolts, etc) stretch @ high rpm, keep it safe at around 1mm ("0.40) less deck is possible with super good quality parts and good blueprinting. That's my opinion ;)

I have run .040" and I measure my stuff out very carefully. At .040" there were "witness marks" on the piston tops. This was years ago with a type 1 main journal crank and Eagle rods. Oh so faint, but still there. These days, I shoot for .050 to .060". I machine my barrels to fit  and I just make sure all my barrels are exactly the same length and that the ends are square with each other.

This is similar:  I've run 0.010" "piston-to-cylinder-top" and then added a 0.040" copper head gasket for a total of 0.050".  I haven't tried to zero it out and run only the copper gasket...it's possible that depending on the type of cylinder, that the piston would contact the copper gasket first...

And i also check piston to wall clearance as many brands uses different kind alloys for the pistons and the larger the clearance the further the piston will rock  and mayby hit the head.
thats how i think of it.

gr henri

Well said.
For an average safe setting the Deck height is 0,040" . The larger the bore the more deck is needed.
My choice would definitely be to make the shims under the cylinders in the correct height and shoot for 0,043 - 0,045" deck, (That´s what I do on type 1´s) and LOOSE the copper gasket! That is one of the reasons why you see witness marks on the piston tops. - They are not steady. I would´nt use them unless I had no other option.
T

Good thread!

I was thinking of running zero deck with a 1mm copperhead gasket but what are the opinions on those? I see a lot of guys running them but Torben you disagree?