VCCA Home Forums TECHNICAL - GENERAL Tech Talk Some more "School is in Session"

In the process of building the engine, taking pictures and writing, I made a mistake. I had to remove the timing cover to take another picture and then did not reseal the cover good. This resulted in an oil leak at the front of the engine, which has proven embarrassing on occasion. {When a Chevy leaks oil we refer to it as, “Marking its spot”, which the Touring did regularly}.

I am in the process of a frame off on my 1928 Roadster and decided I would take the perfect aluminum shell now on the Touring and place it on the Roadster and place the chrome plated commercial shell I have acquired on the Touring.

This made for the perfect time to remove the front timing cover and do it right.

Since doing the “School is in Session” I have received numerous questions and comments about things that were not covered in the School or were not clear. One of them had to do with the lubrication of the timing gears.



How is that for choosing the point where the motor will come to rest? Note the assembly marks are just appearing and aliened at the proper point. Contrary to popular belief, this is NOT top dead center for timing the engine.

Starting with the oil in the sump/oil pan it is necessary to follow its path through the front part of the engine and then back to the sump. The oil pump does two things (and you may remember we discarded the original vane pump and installed a 1936 gear pump) it fills the trays under each rod and provides a signal to the oil pressure gage. NOTHING in this engine is pressure fed. After the trays are filled the rod swings through the tray scooping oil into the rod bearing. It also splashes oil around the interior of the sump. This oil is used to fill 6 reservoirs and mist upon the cylinder walls. Three of the reservoirs are above the crankshaft and provide oil to the crankshaft bearings by the ”˜trickle down system”. The other three reservoirs are above the camshaft bearings. The front camshaft reservoir is the source of oil for the timing gears. Down the side of the cam bearing surface is a small groove that feeds the oil from the reservoir to the front portion of the engine where the timing gears are located. The oil drains into the very bottom portion of the timing cover and in effect is held in yet another reservoir. As this area is filled with oil it builds up to the level of a return hole behind the crank gear back into the sump.



This picture shows the approximate level of oil in the lower timing cover. Unless you have a perfect seal at the bottom of the cover you can see where the oil is going to come out and mark its spot.

When the oil rises to this level, the bottom of the crank gear is submerged in oil and during its rotation carries oil up to the cam gear. As the gears rotate they “sling” oil into a chute. Here is a picture of that chute.



This chute sends the excess oil back into the sump. Now you have seen the oil starting in the sump, the route it takes and then deposited back into the sump.

I have cleaned the front of the block where the timing cover mounts. I have also cleaned the mating surface on the timing cover. A new gasket was cut and both sides coated with shellac. The cover is held in place and the screws installed around the outer edge. One cover screw goes into the block and does not bottom out, as the hole is complete into the block. Those of you who were around for the early sessions of the “School” know where I’m going with this story. Yes, we coat the threads on this screw with the yellow snot.



This is the inside of the timing cover. It is difficult for a large number of people to believe there is NO seal at the front of the engine. The front main discharges the used oil at both the front and rear of the bearing. The oil that goes out the rear goes back into the sump while the oil discharged out the front goes into the reservoir formed by the timing cover. What small quantity of oil that is splashed/thrown onto the back of the timing cover is kept from exiting the timing cover by the small ridge around the hole that the crankshaft goes through. The crankshaft pulley also goes through this hole.

Hi Ray,
On the engine in my '28 truck,the "recovery chute"aims the oil being thrown up by the timing gears back into the trough over the front main bearing.Perhaps this was a way of ensuring the front main got enough oil on long uphill climbs?
What are your thought's on this idea?

Kevin.

I think your reasoning has merit. It would make more sense than just dumping the oil back in the sump direct.

I have seen some engines where a hole is made in the top of the timing cover. I assume the person that made the hole felt that the timing gears needed more lubrication. Any oil placed in that area would be sent back to the sump in quick time. If the area was indeed short on oil he would have more luck if he cleaned out the passage in the cam shaft bearing.

If you are building a 4-cylinder engine it is imperative that all the reservoirs are thoroughly cleaned to include the drip hole to the bearing. Even if you have had the block boiled out these passages must be cleaned individually by hand.

Great job Ray, you have great knowledge. Thanks for sharing.

:)

Ray
It seems MURPHY struck you while you were putting that engine together. I hope you kicked him out this time.
Tony

if the vane oil pump was used from 1914 thru 1935 (27 for sure), why was it replaced with the gear pump and why doesn't anyone produce a vane type rebuild kit if it worked for all those years with the addition of better cleaner oil etc.

$300 is a lot to spend if the old one still works with some cleaning, surface cleaning and some new vanes and springs

thanks ron

Great question. I will see Ray tomorrow and discuss this with him. He should be home late Sunday and will probably respond then or Monday.

Rightly so, go ahead and clean up the vane pump and use it. You may also search my "School is in Session" for information on how to convert a later model gear pump to use in the 1928 engine. The change was made in later years because a gear pump was necessary to provide the pressure for the "pressure" lubrication. The center main in the 1925 was pressure lubricated and was the last one until the introduction of the 6-cylinder engines.