VCCA Home Forums TECHNICAL - 1945 AND EARLIER 1912-1928 Oil restrictor still needed?

Howdy,

I'm replacing the vane-type oil pump in my '28 with a new gear-type oil pump from C&P. Fit right in and all is well so far. I'm not done yet.

Before attempting this repair, I read over the oil pump section of Ray Holland's "School's in Session" rebuild of a '28 engine. Great reading!

There is a discussion about the restrictor that goes in the oil filter line. Do I still need this restrictor with the new gear-type pump?

Thanks, Dean

As the gear pump will give you more flow(and pressure,not that pressure is a real requisite on a 4 cyl Chev),if you have the filter still in line,you could try drilling the hole out to give you more flow through the filter even though it's a by-pass filter system.

I didn't realise there was a restrictor in the filter line? I installed an after market hot rod type filter adaptor plate and a standard replaceable GM oil filter. the whole thing is held in by the original braket under the coil, all seem to work just dandy for the last 15 years. RAY

The oil restrictor is hidden inside a fitting. Here is Ray Holland's verbiage about why it is there:



Below are a couple of pictures of one. The hole is slightly smaller than 1/6 inch in diameter. Since I have a non-standard oil filter, I think I'll just leave out this fitting rather than drilling the hole out.

Thanks, Dean

Hmmm , ok here is a picture of my set up, no restrictor and when hot motor runs 8 to 10 LBs, so al seem good to me, RAY

Just be prepared for your oil gauge to peg out at its maximum reading.A mate put one of these gear pumps in his '28 and the oil was virtually blowing into and straight out of the troughs and he ended up burning out 2 connecting rod bigend bearings,
as the dippers had no oil to fling around.
If your vane pump's in good condition it should supply an ample supply of oil to the troughs.

Thanks for all the info and your thoughts.

It seems prudent to definitely NOT have a restrictor in the line that goes to the filter when installing one of these gear-type oil pumps.

With no restrictor in the line, the maximum amount of oil will go through the bypass oil filter line and help ensure that the gauge and oil troughs are not overburdened or overwhelmed by the increase in oil pressure and flow.

I'll post more info and pics when I'm done with this operation.

Cheers, Dean

Did he have the restrictor to prevent the massive oil flow?

The engine I built in the "School is in session", is still on the road with over 5000 miles. No problems of any kind. There is no position in the 28 engine that needs pressure. We do however, need a reliable oil flow, as the engine is lubricated by "splash" and max flow is desired.

He did have the restrictor on the oil filter,was using a light grade of oil(10W30)as he was running in a near new engine,and his oil pressure gauge ended up destroying itself due to the excessive pressure generated by the pump.Subsequent tests on the pump when he pulled the motor apart for re-building revealed that the pressure relief spring & ball set up in the pump wasn't opening until a minimum of 50psi was reached.

I re-built his old vane pump(bored & bushed the housing,trued everything up)and it's running just fine to this day.He even took it on a 3-4,000 odd mile round trip from his place to the outback through Queensland and back without a problem on the standard oil pump

It may have 'purged' by now, but he should loosen the oil line at the gage, then the engine end and drain all oil from the line. Connect the gage end, then connect the engine end. This should provide the air cushion needed in the oil line to prevent damage to the gage.

He tried all that to no avail.On a test outside the engine with a precision pressure gauge,the pressure relief ball wasn't opening til the gauge read at least 65psi.He tried shorter, pressure relief springs,springs with less tension,thinner spring wire,but couldn't cure the problem,so in went the re'co'd vane pump and no more hassles.
Still running the vane pump in my '28 truck and the gauge shows approx 12psi(not that it means anything)@ 50-55mph on the open road.

The literature that came with my C&P gear pump says that the relief valve is set to open at approximately 60 psi.

Is this setting too high for the 4 cylinder engines? What pressure is too high for the oil to settle into the oil troughs under the connecting rods?

Also, my oil gauge only goes up to 30 psi.

Thanks for your thoughts. Dean

These pumps are copies of the later mid '30's oil pumps that supplied oil under pressure to the main bearings of 6 cyl engines.
Sixty psi is way overkill in terms of pressure for a 4cyl.That's why my mate had so much trouble(and an expensive engine re-build)after putting one of these pumps in his '28.If the relief valves were set to open at a maximum pressure of say 25 psi it'd be better,as all you really need in a 4 cyl is oil flow(read volume)not pressure,as there are 4 open 1/4" pipes feeding the troughs and you won't build up much pressure.As long as the gauge reads between 6-10 psi when hot & running it'll be fine.
The gauges in the 4 cyl's weren't designed for such high pressures and will destroy themselves.Think of the gauge in a 4 cyl as a mechanical warning light.

Howdy all,

I have decided that I'm not going to worry about the increased oil pressure from the gear-type pump, per se, for the following reasons:

1. The inside cross-sectional area of the pump output tube is .049 square inches and the cross-sectional area of all the trough tubes and filter tube (with no restrictor) is .140 square inches: 2.8 times the area of the pump output tube.

2. Oil pressure gauges up into the 1950's were only 0-30 psi, so my 30 psi gauge in my truck should be okay.

3. Ray Holland said that the engine he rebuilt in 2002 has not had any problems so far (with 5000 miles driven).

4. Bill at C&P told me that they have sold hundreds of the gear pump replacements to folks with the Chevy 4 cylinder engines and have not received any bad feedback.

One solution might be for the pump relief valve to open at around 25 psi, but I'm not going to try and change this design point.

I also think that CJP's29 makes an interesting point about the troughs getting 'flushed out' by too much pressure.

Soooooooo, I rigged up a test fixture to see how oil flows into the oil pan troughs at different pressures. Pics are below. Ron Beam and Mark Garcia (South Bay VCCA folks) joined me today for the tests.

Design considerations for the test rig:

1. I already installed the new oil pump in my '28 engine (haven't buttoned it up yet), so I needed different way to simulate various oil pressures. I decided to use air pressure to drive the tests. This way, I could start and stop my air compressor at various pressures.

2. The '28 oil distributor that I used came out of a really yucky, sludged-up engine. I cleaned it as best I could, including blowing air through it, but I suspect it still had some junk in it. The first couple of tests today blew this stuff out, so the later tests are more valid.

3. I plugged up the holes that would go to the oil filter. My reasoning is that the worse case scenario would be an oil filter that is completely plugged. In real life, the oil filter line would relieve some of the pressure that goes to the connecting rod troughs.

4. I used a length of 2 inch pipe to provide the oil supply and pressure. I filled the pipe 2/3 with used motor oil (10-13W) and attached a air gun to the top.

5. I thought that I might need to disrupt (but not restrict) the flow into the troughs because of previous comments in this thread. I put a short, copper tube in one oil deflector. This tube had an upturned tab in it to create turbulence. As it turned out, my patent-pending turbulence generator was not needed.

6. Keep it simple. ;-)

We ran tests at three different air pressures: 30 psi, 40 psi, and 60 psi. Also, we ran these test with and without stopping the oil coming out of the hole that would feed the center crank bearing. Opening and closing this oil flow did not affect the flow to the troughs.

One comment about the 60 psi test. We really needed a larger reserve of oil because the supply tank (pipe) emptied quickly. The first couple of seconds of the video show an empty oil distributor with incoming pressure 'spraying' out an oil/air mixture. Then, just for a couple of seconds, you see the 'normal' flow of oil before the oil supply is used up and a blast of 60 psi air comes out.

Net result (drum roll): oil flowed nicely at all the various pressures and did not flush out the troughs. A pool of oil is always left for the connecting rod dippers to hit.

I decided that the test was not complete without running the new gear-type oil pump in the test fixture. I pulled the pump out of my truck, mounted it in the test fixture, and drove it with a drill. The maximum pressure achieved was 40 psi on the gauge and this pressure was NOT high enough to clear out the oil troughs.

Notice that there is a steady stream of oil coming out of the side of the oil distributor. This stream drenches the middle main crank bearing because it is the thrust bearing when you push in the clutch pedal.

When you have the oil pan off of your engine, make sure this oil hole is not plugged up with sludge.

Before I fire up my engine with the new pump, I will test the connecting rod dipper depth into the troughs using grease in the troughs to make sure that the dippers are dipping into the oil correctly.

Here are pics of the test rig and a video (courtesy of Ron Beam) of the oil flow test.

Enjoy! Dean





And, here is the video: Gear-type oil pump test for 1928 Chevy engine

It'd be real interesting to see the same setup fed from the actual gear pump you're going to use driven by an electric drill to see a constant pressure on the gauge and how fast the oil flow is using it and see the actual flow rate into the troughs.
Don't forget that there is no seal on either the front timing gear cover or for the rear main bearing as well,so maybe with too much volume of oil it'll cause leaks?

I should have added that it'd be good to see an original style oil pressure gauge in the test setup(using the new gear pump)instead of a modern gauge.Then you'd really get a true idea of what would be happening inside your engine

Ask and sometimes ye shall receive.

I pulled the new gear pump out of my truck (1928 AB Canopy Express) and set it up on the test stand. I left the same pressure gauge in the test setup because I do not have a spare older-style one. Also, since I didn't know what pressure the gear pump would generate, using the higher capacity gauge was safer.

To drive the pump, I used my 1/2 inch hand drill. The maximum speed on this drill is 950 RPM, which simulates an engine speed of 1900 RPM. This translates to my truck doing around 40 MPH.

The temperature outside was a nice 66 degrees Fahrenheit and the oil was filtered, used 10-30W.

Note that I still have the oil filter line plugged. Under normal conditions, the oil filter line would relieve some of the pressure that is generated by the oil pump.

The test brings me to three conclusions:

1. When a new gear-type oil pump is installed in '26 - '28 Chevy engines, you should NOT include the original oil restrictor in the oil filter line.

2. The new oil pump keeps the oil troughs nicely filled with oil at all speeds and pressures. The pump does NOT 'flush out' the troughs.

3. The highest pressure seen was 40 PSI. This might be a problem for the original 30 PSI max gauge. However, the 40 PSI was seen with cold oil, a plugged oil filter line, and with an engine speed of approximately 1900 RPM. Considering that I do have an oil filter, if I warm up the engine a little after starting and do not run it too fast, the pressure should be safe for the gauge. I will follow up with more information when the pump is installed and I run it in my truck.

Below are a couple of pics of the latest test setup and a short video of the test run.

Hope this has been helpful. This thread has certainly been interesting and fun.

Cheers, Dean





And here is a video:

Great demonstration. I've asked this question in this forum before but it seems more appropriate here. Has anyone modified their conn rods to actual scoops like on the 29 and later engines. Model Ts have the SAME splash lug on their conn rods and their engine builders strongly recommend that the conn rods be modified with actual dippers, drilled, and grooved like the 30 style. Originally 29 chevs did not have any grooves in the conn rods. I've been told some experienced T builders won't put an engine together without this modification. Any thoughts?

Thanks, beachbum.

I have a set of '29-'32 dippers that I might modify to fit over the tang on my '28 rod ends. The result would be a small scoop in front of the tang that would help direct oil to the oil entrance hole in the rod cap.

Has anyone done something similar?

Cheers, Dean

Go to "School is in Session" for one answer.

Hi Ray,

Yes, I saw that you chamfered the oil inlet holes in the rod end caps so more oil will be channeled into the large rod bearing.

Has anyone used any of the 6 cylinder dippers on a 4 cylinder engine? If so, what were the results?

Thanks, Dean

Consider that other than the rod bearings, everything in the engine is oiled by "splash". That is the reason for the tang that is drug through the troughs. If you put a "dipper" on the rod bearing, that would be overkill for the lubrication of the rod, but would it provide sufficient "splash" to lubricate the more critical areas of the engine? I would not vary from the design of the original engineers in this case.

Reinvent the wheel comes to mind.


If you were to follow my instructions found in "School is in Session", you would improve oil flow to the bearing and still retain the tang for the "splash".

Good points, Ray.

Thanks, Dean

Gear-type oil pump update.

It is installed and I took Justin out for a spin today.

At startup (temperature outside a lovely 78 degrees F), the oil pressure gauge on the dash showed 10 PSI at fast idle. Keep in mind that this is with no restrictor in the oil filter line and with a 1950's style canister filter installed. The oil is new 10-30 dino oil (not synthetic).

After warming up, the oil pressure dropped to 5 PSI when idling and went up to 10 PSI during acceleration.

So, I am not worried at all about my 0-30 PSI gauge in the dash. Also, I have the piece of mind knowing that there is PLENTY of oil filling the troughs.

Cheers, Dean