1949 GMC 228 Engine Oiling issues

[John G]

Working on a rebuilt motor for a friend 228-1949 GMC no oil coming into the rocker arms. Even though I have 61 PSI pressure. from the oil gallery port left side of engine.
Engine was rebuilt several years ago, I have been talk of reassembly of the engine (short block, head already installed by a reputable builder.

 

[Bill Hanlon]

There is supposed to be a small diameter tubing that runs up from a fitting at the front of the block. This picture is a close up of where it leaves the oil gallery and heads up. The other tube exiting away from you in this picture goes to an optional (you may not have it) oil filter.

Below is a picture showing the oil distribution lines on the front of a GMC 6. The green arrow points to the same fitting as shown above and the blue arrow points to the other end of the vertical tube leaving the green arrow. Oil flows from the green arrow fitting vertically and under the thermostat housing to the blue arrow fitting.

First possibility of no oil to the rocker arms is that this tube is not properly installed.

Oil enters the front of the head and through a passageway to underneath the most forward rocker arm shaft bracket (the thing that holds up the rocker arm shaft). There is supposed to be a gasket underneath the #1 bracket to provide a seal as oil travels up through the head and into the most forward ( #1 ) rocker arm shaft bracket.

Second possibility of no oil to the rocker arms is that this gasket is missing, but that would probably not completely eliminate oil flow to the rockers. You can see the marking from the gasket in the next picture if you look closely. By the way, the gasket is NOT SHOWN in my 1939-54 GMC Master Parts Book, but it is listed as "8.0955A Gasket - Valve Rocker Arm Shaft Bracket" part # 105451, washer 3/8. The Maintenance Manual does remind you to install it. Shouldn't be hard to make one.

But the most likely cause of no oiling to the rockers is improper placing of the #1 (closest to the front of the engine) valve rocker arm shaft bracket (the six "stands" that hold the shaft). From above they all look the same, but when you turn them over you will find that two have a machined hole in the bottom that allows oil to travel from the head up to the shaft while the other four do not. One with a hole MUST be in the #1 (most forward) position. The other MUST be installed in #4 or #6 position, depending on where on your engine's excess oil is returned to the bottom to the engine. Note the extra holes in #1 and #4 in the picture below.

Hope this helps. Let us know what you find.

 

[John G]

Awesome, Thanks for the pics, I had figured it out yesterday and then you confirmed it. My oil filter and oil line are all on the drivers side.

 

[Bill Hanlon]

I had figured it out yesterday and then you confirmed it.

My oil filter and oil line are all on the drivers side.

So what was wrong?

Stock oil filters are on the passenger's side.

 

[John G]

This model did not come with a factory filter, it was added according to the owner. The oil galleries are ported and threeded on the drivers side. I did not take the engine apart. It was revuilt by another person. I am trying to figure it our and put it back together.

 

[Bill Hanlon]

Sorry, been away from my computer since last Wednesday when you posted this.

Where does the return line from the filter enter the engine? I can't tell from the pictures.

The filter is either aftermarket or from a similar year Chevy 6.

 

[John G]

Yes Aftermarket, FRAM, Model, Top of Filter to oil pump gallery but lined up with the oil pump outlet to gallery. and bottom back to the low pressure side of the gallery. I read that oil filters were an option on some models, some did not so a bypass filter was installed figuring the oil will eventually all be filtered over time.. ?

 

[Bill Hanlon]

That is not how the original filters were plumbed and I doubt that is how your aftermarket filter should be plumbed.

The original was a "bypass" filter. Only a small portion of the oil passed through the filter during each "pass". The amount was limited by the 3/16" diameter hole in the fitting pointed to by the green arrow that the tubing to the top of the oil filter connects to in the picture above. The source for that fitting is the front end of the oil gallery that feeds your filter on the side of the canister, near the top. The output of the filter (bottom of the canister) feeds a fitting just forward of the distributor near the bottom of the block and fell back into the oil pan.

I don't think your filter will do much at all with both the input and the output plumbed into the same oil gallery with essentially the same pressure on both input to and exit from the filter. The original fitting on the front of the block that screws into the oil gallery has the following restrictions:

Input to the fitting has a 7/32" diameter hole.
Output to the oil filter has a 3/16" diameter hole.
Output to the head for oil to the rocker arms and valves has a 5/64" hole.

I think you have 4 choices.

1. Leave it like it is. Essentially no filtering action and no additional work involved.

2. Remove the filter system and block the holes into the oil gallery. This is how millions of these engines were shipped without filters. It also cleans up the driver's side of the engine.

3. Re-route the output of the filter around the front of the engine to the original end point near the distributor. If this is the choice, I'd put a restriction in the line between the gallery and the input to the filter to reduce flow through the filter and provide more flow to the rest of the engine.

4. The hot rod method: I've attached a copy of California Bill Fisher's "GMC Speed Manual" dated Feb 1, 1953. It shows a fairly easy method to convert the GMC 6 to a full flow filter system.

 

[vwnate1]

Also ;

If you don't remove the end studs & nuts from the intake manifold it's only a matter of time until it crack$.......