I'm rebuilding my 425 for our '67 Toronado, and wonder about the wisdom of the commonly installed oil restrictors in the main bearing area. I'm using a mild cam (near a W30 grind), Edelbrock heads and super low dual plane aluminium intake. The oil pump I found is a Milodon high volume, and the stock Toronado pan (6qt.) I do not plan on high revs or any competition driving. Does anyone have personal experience as I wonder if these have any value, or if there is a possible downside. The idea of too much oil being pulled from the pan doesn't seem like a possible issue, and the design of these small aluminium drilled plugs couldn't prevent that. The engine had covered more than 150 K and when we tore it down it showed excellent main and cam bearings. The bore wear was even within spec so everything seems to have been working well so far. Anyone have any advice?

 

They restrict oil to the cam bearings. Proper bearing clearances are more important, but since it is a steel 425 crank, it won't noodle around as much as a nodular. Bottom line: restrictors aren't necessary in the short block.

 

No need for restrictors and if built with factory range bearing clearances it’s my opinion you don’t need a high volume oil pump, standard volume will be fine. High volume pumps are needed to sufficiently keep large bearing gaps full of oil at sufficient pressure.

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I highly recommend an align hone and balancing.

 

The cam bearings I have seen in the past 10+ years have had ,150" or smaller holes for the oil feed so restrictors are redundant. In the old days I simply drilled new holes 120 degrees away from the stock, larger holes. Never used restrictors. Realize that companies can't sell a hole but they can sell a restrictor plug.

 

X2 never need to put restrictors in the mains.

 

I bought into the restrictor hype years ago. I built a few engines with the restrictors. Then I studied the oil flow diagram and realize the restrictor as do nothing to limit the oil to the top end. And if you need another reason to not use them, one of the engines suffered main bearing damage. During the autopsy, I found the oil restrictor had come loose in the engine, and was sitting on top of the bearing. The restrictor almost completely covered the oil hole.

Pretty sure you can get pushrods with smaller holes on the upper end. That seems to me a much better method to limit oil to the top end. I wouldn’t want to limit oiling to the rockers unless they were roller rockers, the stock stamped steel parts would probably wear pretty fast.