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The Kl 2,5 V6 Head Porting Thread


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Since Mazda cheaped out on the Xedos/ Millenia, and replaced the ZE heads with DE counterparts, performance probably suffered. The still squareported intake manifold matches up bad with the oval ported heads. I therefore decided to do a porting job on the heads, to make the ports match up better. According to Renboy it was “balsy” to perfom this job without dismantling the heads; had to look up that one :lol:

 

Just for the record, I will not take responsibility for anyone experiencing engine damage if attending this porting job. I admit it was abit “balsy”. Further I can’t confirm there are any gains as I have no fore and after dyno or anything. I can confirm that my engine is faster though, but I guess a significant part of that gain comes from the replacement of the knock sensor, which initiated this project. Anyway, for me it is satisfying to know that I did this; a benefit for my general wellbeing. Some says it should give 5 extra hp. I found there would be minor advantages with doing a full portjob with valves dismantled and all, because the inlet channels are fairly smooth and optimized from factory, way better than the IM internals which are rather coarse. Ideally I would have machined the IM inside to give a smooth flow, but that would be impossible with the tools I had, in fact I can’t see how those banana shaped intake runners could be reached with any tool beyond say 4 inches measuring from the heads towards plenum chambers. If ever doing this, I would opt for another IM to work on to limit downtime.

 

Tools needed:

Dremel or chordless drill, steel grinder, vacuum cleaner, ¼”and ½” sockets, pliers, scissors, the old intake gaskets used as reference for the grinding job, a piece of wood adjusted to fit perfect into the IM ports. I preferred my Makita chordless because I was only to machine upwards 15mm’s into the ports.

 

I did of course take precautions to avoid particles entering the Bang premices. They consisted of three barriers:

* Intake valves being shut on the intake being grinded.

* Sponges fit to each valve channel, made of 30 mm fairly dense bed quality sponge.

 

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Abit blurred...

 

* Sponge fit to the intake shape to stop the vast majority of particles. I placed such sponges in all ports, while the inner ones were moved during the process. Obviously I had to see the valves to know they were shut. I also added up with rugs above the sponges on all the other inlets.

 

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Abit blurred too...

 

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Progress from the start:

 

* Remove IM (intake manifold), refer to my Knock sensor replacement guide.

 

* Jack up the front passenger side, support the car and take off the wheel.

 

* Take off the passenger side splash shield.

 

* Place a 21 mm socket on the crank pulley bolt, and turn the engine untill the intake valves on #1 cylinder are closed.

 

* Place sponges as shown in pics above, make sure their fit is precise.

 

* Fit the old IM gaskets and secure their position with a distance and the outer nuts, see also pic above. Opt for leaving about 2 mm distance to the gasket edge, as this is the case on the IM.

 

* Machine each corner untill the distance to the gasket is even, checking with the piece of wood during the process. Opt for an angle giving about 12- 15 mm maximum depth. Be sure to support the grinding tool with both hands, to prevent it from vibrating and jumping all over the port.

 

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* Use the vacumm cleaner to remove the particles. I used an ash remover to catch the particles before entering the vacuum cleaner, through a piece of garden hose.

 

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This port is finished, compare to the other yet to be treated for reference.

 

* Use a narrow pliar to pick out the outer sponge. Then use the vacuum cleaner again, to catch the particles passing the first sponge, mainly during removal. Use a good light, because the alloy particles will shine bright.

 

* Repeat this procedure on the inner sponges, and check if any particles have reached further. If that is the case, use the vacuum cleaner once more. Then, as a final step, use a small piece of sponge taped to the tip of a small screwdriver to wipe out what is left, if any. This way there should be minor risk for anything reaching the cylinder. I concluded with compressed air being a bad idea; it will do more harm than good with risk of alloy chips all over the place.

 

* When all looks good, make sure the outer sponge is free of remaining particles and replace it. Then turn the engine until cylinder #2 inlet valves are shut. Repeat until all cylinders are done. I spent three nights on this procedure, probably 3 hours on the first port to figure out the best method and about an hour on each of the rest. Just as well it’s not a V12…

 

* Be sure to remove any remaining particles, both inside the V, on the gasket surfaces after removing the old gaskets and on the valvecovers if spotted.

 

* Remove all the sponges, and do a final inspection in each port for particles.

 

* I also knifeedged the dividing wall in the IM, again with sponges fit to avoid particles from going into the IM. I cleaned the EGR ports too; one of the holes was partly clogged. I used a tiny screwdriver to pry the carbon/soot particles loose, and removed them with the vacuumcleaner added up with airhose from the EGR valve ports towards the IM ports.

 

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Before treatment.

 

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After treatment.

 

* Refer to my Knock sensor replacement guide for refitting the IM.

 

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