A little more on cores. Six fins is probably aftermarket even though I did find find one for a 5X D6D machine that had 5.5 fins per inch but it was listed as a trash core. Less fins to let the debris flow through was that theory.
Most aftermarket manufactures used less fins per inch, thinner headers and maybe thinner fins. Copper or steel fins are an option also. A little less here and there lowers the cost. Usually everything works out OK but sometime it doesn't.
Not all aftermarket manufactures are cheap. If you are needing to buy one find out the specs they make there cores to. Of course they'll all say OEM specs so ask them for their dimension.
In the 1980-90s the company I worked for (and still do ) sold 6-800 cores a year, all for Cat. Undercarriage was our main business but we had lots of non-undercarriage parts also. Around 2000 we went strictly undercarriage so I haven't dealt with cores since then, but still remember a lot about them. We purchased all our cores from a company called Dynacore. Dynacore was owned by a parent company called General Thermodynamics. GT was OEM supplier to Cat. I did all the purchasing and dealt with the top person at Dynacore. He told me that there was only one assemble process and all cores were built to the Cat specs. They put the cores going to the OEMs in one crate and market it with Cat numbers and information. They put the aftermarket probably in the same crate, and they were really nice crates, but were marked with the aftermarket part number. I never went to the factory so I can't say if that's true but we never had any problems with them and they were the same specs as OEM.
