VCCA Home Forums TECHNICAL - GENERAL Mechanical - Engine, Trans, etc 1939 tune up

Since I have my car running rather well, I decided to check all the tune up stuff. The dwell of off a little, the plug gap was off a little, timing was good, but the valve lash was wide. The exhaust valves were about 0.020" and the intakes were about 0.012", hot. So before I tried to set the valves I removed the rocker assembly and cleaned it up, torques the head bolts, and re installed the rocker arm. After warming up the engine, I set the valves on the loose side 0.008 to 0.009 on the intake and 0.015 to 0.016 on the exhaust. The engine will idle down to 400 rpm and run smooth with a vacuum of more than 20. The engine quieted down, there is still a small tick, but much better.

I have a question. There doesn't seem to be a lot of lube on the rocker arm. The oil pressure (according to my dash gauge is nearly 15#, but will drop when warm to about 10#, depending on engine speed. The supply pipe in the middle of the rocker arm has a flow coming out of it. If I plug it with my finger, the oil will come out the vent hole at the top. BUT there doesn't seem to be any oil coming out of the rocker arm holes, especially at the ends. What is normal? should there be oil squirting out of these holes? Thanks Mike

Did you clean out the sludge from inside the rocker shafts? Are the rocker arm bushings worn and oil groves shallow?
NORMAL IS SOME OIL COMING OUT OF EACH HOLE AT IDLE AND OIL COMING OUT OF ALL HOLES WHEN YOU RACE THE ENGINE.
at idle with hot oil a 1937-39 will register only a couple of pounds at 400 RPM. The oil pump was improved in 1940 to produce more presure at idle.
I always set the valves at .006 and .014 on my 1939 with no problems and idle speed more like 600 RPM (for several reasons)

The rocker shafts a very clean, inside and out, but I didn't look at the bushing for wear. I'll have to check that later. If they are worn should I see oil leaking out the sides of the rocker arms near the center of the rocker shaft? I did block the supply pipe and vent with my fingers and some oil did start to come out the middle holes at idle. Suppose I need to do more checking, THanks Mike

This morning I removed the rocker arm again. It is absolutely clean, all holes are open. The shafts are smooth, although you can see that the bottom, where the arm wears is shiny. The arm bushings also show a shiny spot on the bottom. I measured between 0.002 and 0.003" clearance between the shaft and the arm bushing. The grooves in the ar bushings are open.

I have a question. There is a hole in the rocker arm shaft that supplies oil to the arm. I found the shaft orientated so that this oil is on the bottom. This means that the oil has to pass through the groove to get to the oil hole on the top of the rocker arm. Should this oil supply hole in the shaft be on the top? Mike

No, the oil holes go to the bottom where the pressure of the arm to the shaft is. The top of the hat and arm opening has no pressure and requires next to no lubrication.

years ago the trick was to squeeze the overflow oil line together so less goes to the over flow and more to the rocker arms.

I thought of that too. But what I'm going to try first is to deepen the grooves in the arm bushings. Although the bushing are snug to the shaft, the grooves are very shallow. In fact in some places they are not there at all. Thanks for the help, Mike

I removed the front half of the rocker arm and opened up the arm bushing grooves a little. The original grooves were rather square. I used a round burr in my Dremel tool to open up the groove. After reassembly, now all the front half arm holes is producing a little oil on idle, except #1 intake. Maybe a little more is needed here.

The bolts that go thru the pedestal posts have shoulders that mostly plug up the hole so that oil can not come out. I don't see any oil leaking here, but should there be a washer under these bolt heads? AND the stud that holds the valve cover down does not have a shoulder, but does have a washer. I don't think this is a leak problem, at least at idle.

Also the oil fitting between the front and back arms maybe a problem, seems that depending on how it is placed, it can leak. I have another one maybe it will work better. Thanks Mike,.

I found my spare oil adapter. An odd thing, the original one from the car has a larger hole going to the back half of the rocker arm, whereas the spare has a much smaller hole. Any ideas on this? You would think the back half would need as much oil as the front. Mike

I wanted to show a picture, but can not figure out how. The large hole is about 1/4" whereas the small hole is about 1/16".

There are special washers under ter rocker arm bolts and stud nuts. They are thicker and very narrow. I would think Ace Hardware would have some thing that will work.
The bolts are special (thicker on top) so if the shaft s up side down the will not fit into the slightly tapered holes in the shaft.
I can not picture "oil adapter" mentioned but they did restrict the flow to the back of the engine to eliminate excessive oil leakage at the back of the valve cover.

Note the the rocker arms and oil pan trough tubes get only low oil pressure from the oil pressure regulator. That is one of the reasons I prefer to set my idle speed a little higher to get more oil up to the wrist pins at idle speed....also turns the fan and water pump faster for better cooling at idle.

What I'm talking about is thespring loaded brass oil supply connector, between the front and back roacker arms. I'm having a little trouble sealing it. Oil is dripping out at the rocker arm connection. Today I want to try and clean it up and apply a little permetex, to try and seal it a little better.

I'll see if I can find some washers. I didn't realize that the arm shaft had two different size holes so that you could only assemble it one way, so the oil holes of the shaft are on the bottom.

Somebidy mentioned that a 1940 or 41 oil pump produced higher oil pressure. Could one of those be used in the 39 engine? Mike

Yes, the 1940 and up oil pump produced more pressure at idle speed. Will not work on a 1939
I would not used anything to seal the normal dripping aound the comnnector.

OK, I get about 2 drips per second on the front connection and nothing on the back, so maybe that is OK? I have to reset the valve lash. I've been setting them a little loose 0.008 on the intake and 0.013 on the exhaust. Seems quiet to me, but my hearing is not as good as it was.

One other item, at idle speed between 400 and 900 RPM the engine seems smooth, but if I adjust the idle speed to 1000 there seems to be a miss. I can hear it in the exhaust. Yet I do not notice it while driving. Mike

Too much oil dripping from the valve train results in pooling and leaky gasket. You only need enough to keep the rockers lubricated.

Modern high octane rated gasoline burns slower than the engine was designed to run. An occasional miss is expected particularly at higher engine speeds. It can be minimized by increasing timing a degree or two and/or increasing the spark plug gap.

That is about the speed the carburetor goes from the idle circuit to the run mode. The mixture may be a little lean at that throttle opening and nothing to worry about as 1000 RPM is not a usual driving speed. Also if you install a 1941-1949 Carb. on a 1939 the engine will have several speeds where it rins too lean and has a slight surge, especailly over 45 MPH.
I played with a lot of Carbs with my '39.

That is also the point weRe the throttle plate is open far enough to get the vacuum port to the vacuum advanCe open and the timIng is advanced. Under no load this wil make the engine lope, eVEN at higher rpm'S.

A bunch of years ago I purchased a large box of carburetors, mostly W-1. In it, I found a Carter 420S, which I believe is the carb that was used on the '39. I rebuilt it and it runs quite well on my engine. I noticed what you are talking about with some of those other carbs.

I did have an odd problem. After I set the valve lash, I had a clicker. Found it and adjusted the click out. Then I went for a drive and the engine didn't have power and was missing. Geezzzz...... Checked the valve again, OK, carb OK, points, OK, manifold tight and not leaking. Then I pulled the plugs. I found one plug with a glob of stuff stuck between the electrodes. I must have set this plug into this mess on the bench, while setting the valve and not noticed. Another lesson in keeping a clean work area. Cleaned the plug and the car runs very well.

So I think I improved the rocker arm lube, quieted the valve noise down and tuned her up some. Now, if only I could afford a new set of tires......... Thanks for the help, Mike