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Subaru cylinder head exhaust bucket galleries block-off

Practical Engine Building

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Hey Guys,

I just listened to podcast#37 with Dan from Vermont and it was interesting to hear that they do block off the oil galleries for the exhaust valve buckets and probably for the cams as well if I understood correctly, and all this is done to improve the oiling of the main bearings.

I checked the OE drawings of the lubrication system, and I can't seem to find an easy point in the gallery tunnels that you could just block off, so I was wondering if anyone has any ideas about that and also would be interested in hearing your understanding of the exhaust cam related gallery blocking too. Did I understand well that they block that too along side the buckets?



Blocked or restricted? If you could post a link to the podcast in question, it would help.

It's not uncommon to use restrictors in engine cylinder heads to prevent over-oiling and oil build up in the head area, and to direct more oil to the crank to lubricate the mains and big ends - but I would be very hesitant completely blocking any oilways - they're there for a reason.


from 19:30

and attached is the picture from the Subaru manual

Attached Files

Ah, thank you.

The chap is talking about a very specific application and, within those constrains, there should be enough oil splashing and draining down to lubricate the exhaust cam's, lobes and buckets. It isn't clear if he blocked off the oil feed to the camshaft bearings or possibly oil squirters - the former may work of there was enough oil splash, but...

Unless you are looking at a similar case where the hydraulic cam followers have been replaced with solid lifters, you will be turning a lot of rpm pretty much all the time, expect frequent tear-downs and checks, and preferably be using DLC coatings, I would strongly advise against blocking the oil feeds off like that.

If you were an experienced builder, and were prepared to experiment even if it cost an engine or two, drilling and tapping the oil feeds for restrictors may work quite well, but I'd be loathe to recommend it unless you were confident on what you were doing and prepared to lose that odd engine.

Thanks for your insights Gord.

So, yeah, me being an enthusiast, for sure would not like to scrap an engine, but I am certainly interested trying new things if possible.

Now, these heads don't have hydraulic lifters from the factory. The cam lobes are pushing on the valves directly through the buckets sitting on top of the valves.

In the meanwhile I checked the galleries on my old engine that is on stand, and actually each bucket could be blocked off or installed an individual restrictor.

Will see if I will want to try that.



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