Copper cylinder shim help

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neeper

neeper

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I got the 30.5cc Big-Bore Combo Kit 3.75 HP - ca370+dd3x from DDM and unsure which gasket goes first on the crank case, copper shim gasket or the blue gasket? Or does it not matter?

a) Crankcase > Copper shim> Blue gasket > Cylinder head
b) Crankcase > Blue gasket > Copper shim> Cylinder head
 

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neeper said:
I got the 30.5cc Big-Bore Combo Kit 3.75 HP - ca370+dd3x from DDM and unsure which gasket goes first on the crank case, copper shim gasket or the blue gasket? Or does it not matter?

a) Crankcase > Copper shim> Blue gasket > Cylinder head
b) Crankcase > Blue gasket > Copper shim> Cylinder head
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I have no clue, I don't think it matters ? if anything I'd think the blue paper gasket would go first ? hope someone else can tell you. I'd email DDM for their input
 
You need to check your squish and gasket thickness. If you have 0.020" with just the copper gasket then you don't need the paper gasket. And I wouldnt stack paper and copper anyway. All you need to check squish is some soft solder and a caliper.
 
+1 Seandonato73's comments. You have 2 different color coded thickness gaskets which alter your squish clearance. I believe the safe spec is between .011 and .020" but do your research to be sure. Keep in mind, slightly more squish is better than less for reliability.
 
Polar_Bus said:
+1 Seandonato73's comments. You have 2 different color coded thickness gaskets which alter your squish clearance. I believe the safe spec is between .011 and .020" but do your research to be sure. Keep in mind, slightly more squish is better than less for reliability.
Click to expand...
Yes to what polar said. also be careful on the clone cases as crank center and top deck have a way of wandering around a bit so keep that in mind on squish settings.
 
Agreed, that's why I threw in the "greater squish" disclaimer. I forget where I learned of the squish specs, I think I was watching a performance engine rebuild vid on Youtube. I searched high and low for a factory squish spec but never found one. I checked my documented CY 36cc engine specs and with a "no name" paper base gasket i'm at a whopping .028" of squish. I ordered a few different thickness copper base gaskets from DDM and will play around with tightening up my squish over the winter. My engine runs excellent so no problems running a large squish.
 
The only thing I found with less squish with the clone motors is that their wrist pin bearings get beat up. if those motors are tore down and rebuilt right when new they are a good motor, I would like to tinker with one of the rovan 36s. the 45 runs pretty good once you put the right shorter reach plug in it. The standard plugs reach almost to center of dome!. That 45 degree plug angle puts it there. the short CMR7A puts it perfect in dome wall. that rovan 45 cylinder is a clone of the G45 zen airplane cylinder and that is how we found the right plug.
 
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You can go less just don't expect the engine to last as long. I did an old stihl 031 for a friend, ported all the bells and whistles. Decided to delete the base gasket. Ended up with 0.009" and it didnt last long. Had to eat a crank and wrist pin/ bearings. Same top end went back on after second rebuild I bought some shim stock and made my own base gasket set it to 0.020" and shes been living a long happy life. Although it was a bit slower in the cut then before. And it's been running that way for a few years now. Ever since then I've just stuck with 0.020"
 
I seen thicker plasta gauge at speed shop for checking the rotors on superchargers. It was a nice .032 to start. would work slick for this!.I do believe it said BDR on peg card.
 
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