Rocker Arm Lubrication


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By BudMan - 13 Years Ago
Most Y-Blocks have over flow pipes at the rear or front of the rocker arm. I understand that this is to direct oil flow from the rocker arm back into the engine. My newly rebuilt 312 does not have these overflow pipes and the holes are plugged with a square head bolt. My question is, are the overflow pipes required and necessary and will the arms get proper lubrication with them plugged? I read the archive posts relating to rocker lubrication and did not see a definitive answer.
By MoonShadow - 13 Years Ago
Plugging the returns was to keep oil in the top of the valve train longer. Another fix for bad oil (not oil pressure). Those tubes also feed oil to the front and rear cam bearing. I don't think I would block them on a street engine. Chuck
By aussiebill - 13 Years Ago
MoonShadow (12/9/2012)
Plugging the returns was to keep oil in the top of the valve train longer. Another fix for bad oil (not oil pressure). Those tubes also feed oil to the front and rear cam bearing. I don't think I would block them on a street engine. Chuck

Chuck, i was curious with this "Those tubes also feed oil to the front and rear cam bearing" , not sure about that, as the cam brgs are fed from crank mains arnt they.Smile And Merry Xmas to all.

By Ted - 13 Years Ago

Where the valve spring pressure has been increased, blocking off the overflow tubes at the rocker arms does help to increase oil flow at the rockers.  This does reduce the amount of oil to the front timing gear area which can be compensated in other ways.  When using stock valve spring pressures and keeping with the original design, any excess of oil is simply redirected to the front timing area and the distributor gear when using the overflow tubes.  Advantages of using the overflow tubes includes reduced heating of the oil within the rocker shafts and eliminating trapped air in the shafts.  Keeping the oil moving is going to reduce any sludging taking place within the shafts.  While I use pressurized oiling at the shafts on my Y powered race engines, my ’55 Customline with over 250K miles does still use the stock rocker arm overflow tubes and still marches on like there’s no tomorrow.

 

Here are links to past threads that touch on this subject.

Center cam bearing

Grooving the center cam hole in the block

Oil Flow Diagram

Pressurized rocker shafts

Pressurized rocker shaft more

Pressurized timing chain oiling

Rocker arm overflow tubes Cons

Rocker arm overflow tubes Pros

Rocker arm overflow tube More Pros

Slotting the rocker shafts for improved oiling

Timing chain oil trough

Adding lifter valley holes for camshaft oiling

Drilling additional holes for oiling and/or venting

Valley holes for aiding crankcase evacuation

By BudMan - 13 Years Ago
Thank you very much for all the references to rocker lubrication. I read them all and the conclusion that I came to was that there is not a consensus on whether it is good thing to plug the rocker arm overflows. So I decided to defer to the engineers that designed the engine and I put on a set of overflow tubes that I took off a 272 that I have. Since I am not building a go fast engine, I should probably do what the engineers intended. I will probably start this engine for the first time in the next couple of weeks and I'll see how that goes. When I had both engines in the garage, I noticed that the push rods were a different diameter. I thought all y-block push rods were interchangeable. The 272 was .250 " and the 312 was .333. Again, thanks for the help.
By MoonShadow - 13 Years Ago
I knew we needed oil to the front and year. I stand corrected that it is for the dizzy gear and timing chain. At least they are sort of close to the cam bearings! Chuck
By Hoosier Hurricane - 13 Years Ago
Budman:

The pushrods before 1960 were solid, about 1/4" diameter.  In '60 they became tubular, about 5/16 diameter.  Aftermarket replacements are the tubular type.  Racing aftermarket are bigger yet.

John

By lyonroad - 13 Years Ago
moonshadow et al , my '55 292 has overflow tubes (small copper tubes) to the rear only. Are they supposed to be at the front as well?



Mark
By MoonShadow - 13 Years Ago
I may be wrong but I thought they were front and rear on opposite sides? Chuck
By charliemccraney - 13 Years Ago
The rocker assemblies are assembled in the exact same way; When you have them off of the engine and right next to each other they should look exactly the same. This puts one tube at the front and one at the rear when they are installed. I think the driver side is at the rear and the passenger side is at the front.

If both are at the rear, then one of your shafts is probably assembled incorrectly and the rockers are not getting oil as a result. Check them!
By lyonroad - 13 Years Ago
Oops, you're right. My engine is on a stand, up against a wall and I have been looking at the drivers side most recently. This morning I started disassembling the engine to do a rebuild over the winter and find of course that the passanger side overflow tubes are in fact at the front. Sorry about that.



Mark
By Rono - 13 Years Ago
On the blown stroker motor I'm building, I cut the ends of the overflow tubes square and then tapped them with a 12-24 tap. I used 12-24 set screws and drilled a 5/64 hole through the center. The screws are pretty hard so I had to be patient and go easy. I screwed them into the ends of the tubes with red Locktite. Now that it's done, I'll have the shafts pressurized and still have lubrication to the timing chain and distributor shaft.

Rono