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Hey I have a 1984 FB that had a 13b swapped into it and I’m trying to figure out what year the block is. It has R5 cast into the front iron and I haven’t been able to find pictures of rotor housings that have the Mazda in the frame and the 13b higher up everything I’ve seen has them together
the engine is from 74-75 rx or repu. same engine as i'm running from a 74 rx4. only pic i have on here is in the gallery.
mine had the egr in the top of the center housing where urs doesn't so might be 75. not sure when/where that changed.
I’m currently using a 20w- oil with a front mount cooler, a 160° thermostat, and I’m running mix gas at a 2 ounce to every gallon ratio. Does all of that sound about right?
If it has iron seals then you'll be wanting that 2 oz/gallon, that is what I run on my bridge port ('82-85 end housings, GSL-SE rotor housings and intermediate housing, FC rotating assembly) with steel Atkins seals. My rotor housings look much better compared to running less oil. This also does not result in heavy carbon deposits, two stroke oil doesn't have unburnables like engine oil does.
Your engine is old school enough that it may have carbon aluminum apex seals. Look through an exhaust port and see if they are 2mm or 3mm, and see if a magnet sticks to them.
I run 1oz/gallon in my 12A but that includes having a functional OMP. I do run oils engineered for Diesels with DPFs, on the theory that they make less ash and deposits.
74-75 Rotor housings, and 74-81 Irons (it has the screw in heater hose fitting), may or may not be a factory assembly (it looks ported)
If all of the side housings are from the same year 12A, then they are from an '81, since I am fairly sure that was the only year that had the tall primary ports, screw in coolant fitting, and the air injection passage under the primary ports.
I'm curious if the rear has the passage for the oil pressure sender drilled out. '78-80 RX-7 did not have that. Unsure about RX-3/4/5.
07-13-21, 03:01 PM
