![]() ![]() If your barrels bang into the heads on the outer surface near the fins, the spigot hole is too deep, you need to use sealing rings. Nowadays, the only reason you want to use the sealing rings is if some knucklehead over-flycut your heads. (*canaries: blown sealing rings are not a primary cause of leaks but symptoms of loss of clamping force*) If you overheated the engine, they would indeed be prone to leaks as the clamping force dropped due to overexpansion squishing the case spigots/head spigots/sealing rings themselves. They did serve as "canaries in the coal mine"* as far as head leaks. 028"and were designed to cover up the usual tolerance discrepancies found in mass-production. 030" that I have found to squish pretty consistently down to. The sealing rings from the factory were usually. You want to adjust your deck height exclusively at the bottom of the cylinder barrel, it is best-combustion-physics to have that piston as close to level at the top of the cylinder as possible without getting too close to the valves. The rings at the bottom of the barrel are called shims, because that is where you adjust the deck height, thus they serve as "shims." The rings at the top of the cylinder barrel are called sealing rings. Please let's get our nomenclature straight. Vwlover77 wrote:So, what values do I want to plug into a CR calculator?ĭeck Height = Measured value +. Look at your old intake/exhaust gaskets too, see if there is any mismatching between ports and manifolds/runners. As you work with your engine, make all cylinders configured identically so they will behave similarly. At idle, any discrepancy in the engine's air pumping flow characteristics will show up soonest. Idle quality is most affected by camshaft lobe identical lift/lack o' overlap/identical lifters, calibrated clean injectors with good seals, clean tight manifold gaskets on clean straight phenolic spacers mated to a clean straight manifold flanges, tight exhaust components, identical combustion chamber cc's/deck heights/valve seating depth, clean ignition performance, etc. I think you might have a stack-up of variables all conspiring to wreck your idle. ![]() I was pausing here because Jim from Air-Cooled Ranch had mentioned that he did not think the "Torque Special" was actually a very radical cam.īut, I do NOT want to put everything back together and wish I hadn't! 050 between piston and cylinder edge, cylinders torqued down to about 20 ft/lbs with nuts and washers on each head stud corner. It is nice, of course, to get the piston further out towards the edge of the cylinder. But, I do not acutally know your combustion chamber volumes. 028 sealing rings (if your flycut will allow you to) will give you a 7.5:1 compression ratio, which is perfectly acceptable. If you have the deep 15cc dished pistons, then deleting the. The need for a cylinder head sealing ring may have been caused by the usual bugaboo, too deep of a flycut. you are spot-on with a 7.3:1 compression ratio. Would these deck heights, with the additional clearance of the shim, result in too much deck height?Īssumption I : you have 7mm shallow dish pistonsĪssumption II : you have 52cc combustion chambersĪssumption III: you have that. I don't know if that would indicate that these heads have ever been flycut or not. ![]() I have not cc'd the heads yet, but on both heads, the cylinder mating surface is approx. ![]() I bolted the cylinders down and took measurements between the top of the cylinder and the top of the piston right at the outer edge of the piston, at 12, 3, 6, and 9 o'clock positions. I pulled the heads tonight, and measured the deck height of each piston as best I could with my digital caliper. Vwlover77 wrote:Jim at the Air-Cooled Ranch suggested that too much deck height might be the reason why the CB Performance Torque Special camshaft in my engine idles so poorly. ![]()
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