I have a 49 216 engine that I have converted to full pressure oiling (drilled crank - rods oil via mains). I have seen posts where the rocker oil return line was pinched to run more to the rockers. I also saw one comment that the purpose of the return line was to provide oil to the distributor drive gear.
My question is, would it hurt to pinch the rocker return line closed?
Thanks.
Larry
Larry
46 Chevy 1/2 ton stake - family truck for 78 years USAF 75-81
If you are referring to the oil connector in the middle of the rocker arm assembly, you do not want to pinch that completely "shut/off". A little oil has to go the rocker arms and that oil drips out and returns down to the oil pan.
Tim I think he was referring to pinching the end to increase pressure to the rockers rather than cutting off all flow. Larry, if I'm wrong with that assumption please correct me. I'm certainly no expert but IMHO any gain in pressure would be negligible. It's open on my '38.
Save a life, adopt a senior shelter pet. The three main causes of blindness: Cataracts, Politics, Religion. Name your dog Naked so you can walk Naked in the park.
OK, sorry, I misread "My question is, would it hurt to pinch the rocker return line closed?"
But, my advice was/is still correct.
Pinching the "return side/line of the fitting" would serve no purpose with fittings with sealed "return line/side", depending on what you mean by "return line" or "return side".
Such as the fitting shown below, left (59-63 rocker arm assembly).
The fitting shown below right could be pinched (or, the "window" could be closed).
Which year/type connector do you have (see link in above post)?
Oh, by the way, I have not seen a concern about this, relative to any of those fittings: "I also saw one comment that the purpose of the return line was to provide oil to the distributor drive gear."
Maybe Pre-'68 Dave will comment on the effect on lubricating the distributor drive gear?
Larry, I can't speak to the 216 but can a 235 if you want to draw a comparison. The picture that Tim attached is a good reference. The various oil feed connectors before 1959 had a return loop where Tim's picture shows the pinched end. They were designed to allow enough oil to flow to the rocker arms with the excess returning to the oil pan through the pushrod holes.
Many owners/mechanics pinched off the loop on the return side to force more oil to the rocker arms. The oil still ends up returning through the same path, just more goes through the rocker arm shafts to the rocker arms. This was a very common practice.
What I find interesting is that in my experience, more 235's have had the fitting pinched off than have been left original. It is much harder to find an unmolested one than a pinched off one. A couple years ago, I was helping a fellow 'bolter find an unmolested one, so I went looking in my usual spots. I checked about twenty engines at a couple different yards and only found two that were unmolested. Maybe that was a fluke, but I found it to be interesting.
Would you hurt anything by pinching it off? Probably not. You'd force more oil to the rockers. Is that how the GM engineers designed it? Nope. Have thousands of people done it before? Yup. The only risk that I would see is that you might slow down the rate/volume of the return oil by forcing it through the constrictions on the rockers, but if that was a problem, I'm sure the practice of pinching the line would have stopped long, long ago.
Want another worthless bit of trivia? I've seen two different ways to pinch off the line. One way was to cut it off close to the top of the loop then crimp the cut end in a vice. The other way was to leave it intact and use a cold chisel or a crimping tool to notch the line at the top of the loop. Maybe for aesthetic reasons, maybe for performance, maybe didn't think about it too much, dunno. But I've seen both ways, so I decided to test them. The ones that are cut and crimped in a vice aren't completely sealed, but barely allow a drop of oil to exit the crimped end. All the oil has to flow through the rocker arms. The ones left intact that are notched are not sealed as tight and still allow some oil to flow through the return loop as intended, but restrict the flow so that more goes to the rockers.
Leaving the line intact and notching it seems to be the best hybrid approach IMHO. Not sure that it matters. That's what I have on my 235.
Starting in 1959, the return side was pinched off by design because the rocker arms were changed to offset oil grooves and the pinch helped to pressurize the shafts with the new design.
the oil will still get to the drive gear, it doesn't need very much oil. The biggest reason to have a large volume of oil in a bearing surface, (gear tooth mesh being considered a bearing surface in this example) is to draw away the heat caused by pressure/friction between the surfaces. The actual lubrication takes very little oil. Two examples that I know someone will say is apples and oranges, but gonna do it anyway. We have centrifuges at work with approximately 8" diameter roller and ball bearings, the rotating assembly weighs 8400 lbs, and spins 2800 rpm. The bearings get 2 drops (.06 cc) of oil every 5 minutes, that takes care of the lubrication, the oil is transported with compressed air @ around 15 PSI, the air does the cooling. I used to work at a dairy processing plant, and everything was stainless steel, and you most likely know the trials of trying to work stainless, we tried every concoction on the face of the earth to prevent burning the tools, what we ended up that worked the best was just a jet of compressed air aimed directly at the contact point of the tool, as long as it was kept cool, you could cut all day long.
