Hi guys,

I have a freshly rebuilt Pontiac 400 motor in my 1968 Firebird. One minor snafu during the assembly is I forgot to install the oil pump intermediate shaft before the oil pump, so I ended up having to file off the "ears" from the intermediate shaft and install from the top.

I installed the motor in January of this year, and shortly after installing, poured 5 quarts of oil over the valves before installing the valve covers. I then proceeded to prime the oil system using a priming shaft hooked up to a drill, which I ran counter-clockwise for approximately 5 minutes. The oil system built approximately 60PSI of oil pressure, and I could clearly see oil coming out of the pushrods and into the hydraulic lifters. When I spun the priming shaft by hand, I could feel "hydraulic" resistance.

The project then got sidetracked for a couple months, and the motor was not actually started.

This month, I've started focusing on the car again, and decided to prime the oil system again before starting the motor up for the first time. However, now I can't seem to get oil pressure to build. When I spin the priming shaft by hand, I feel zero resistance-- it's as if the pump is just pushing air around. I've been very careful to make sure the intermediate shaft is engaging properly with the "gear" on the top of the oil pump, and that the priming shaft is engaging properly with the intermediate shaft. I've inspected the "gear" on the oil pump with an endoscope and it seem to be in tact. Yet when I spin the oil pump with my drill, I get zero oil pressure, and a very "hollow" sound, as if the oil pump is just pushing air around.

Here's an audio recording of the priming procedure.


(https://www.vimeo.com/402816143)

As you can hear, it is a very "hollow" sound, and there is zero oil pressure.

Any ideas what could be the issue? I've made sure that I didn't mysteriously lose oil-- there is plenty on the dipstick.

It is baffling to me that this priming procedure went smoothly a few months ago, and now isn't working at all.

Your suggestions are greatly appreciated!

Now for the dumb questions. Is it an electric or mechanical gauge? If electric, power on? I just did the same thing recently and primed with a cordless dewalt drill and could feel resistance. You should be able to feel the torque as it pumps. Did you give it enough time to fill the oil filter?

Next dumb question...are you sure your turning the pump the right direction? I’d run it both ways for awhile. Won’t hurt anything to run it backwards. Did you run it long enough to pick up the oil? Maybe try over filling the crankcase with some extra oil. You can always drain it back out later.

Mechanical gauge... it's definitely not a gauge issue, as when rotating the pump by hand, I can tell that there's no resistance. Either the pump isn't working (perhaps something got destroyed internally) or it is spinning air

When I primed the system back in January, I felt resistance immediately, and the oil filter was certainly filled with oil after the 5+ minutes of priming. I assume that the oil is still in the filter.

If it's not something dumb like turning the shaft the wrong way or you drained the oil and forgot, you have an oil pump issue of some kind

Yes, pump is being turned CCW, and yes, I've tried running clockwise as well.

I definitely didn't remove oil, and if it leaked out, it would be obvious on the gravel underneath the car. But there is plenty of oil on the dipstick.

My plan for this weekend is to overfill the oil a bit and see if the situation changes. If no change, I'll drain all the oil and stick my endoscope through the drain plug hole to visually inspect the oil pump. Perhaps remove the oil filter housing and blow compressed air through the oil valley to see if the oil pump "gear" on top will spin via air pressure. Then, add oil back and see if any change in the situation.

A couple of other things it could be. Pickup tube fell off. A piece of garbage holding the bypass check ball open allowing the oil to just recirculate back into the pan. Or one of the oil passage plugs have fallen out( I think you would probably still feel a bit of resistance in this case though).

Hi,

I did a 400 HO and a 389 a couple of years ago. Have a look at my videos. I built a engine test cart.

I don't believe you will feel much resistance by turn by hand unless you have a lot of mech adv with your tool. Just put the tool in and run her with the drill. See if you can feel the torque and the oil flow. Also, do you experience rebuilding this engines? I'm assume you know how to break them in.

See what reading you have on your oil pressure gauge (oil in a tube type of gauge)..

I'm a little concerned about the grinding off the barb on the oil pump rod. We made the same mistake but fixed early on. When you use a test stand it makes life worth living !! lol It's so sweet when you can do a job, just yourself and no climbing under the car, everything is just right there front of you.

Gus,

I wish I had the resources to build a test stand! Definitely would have liked to do the engine break-in on a test stand! I resolved the issue, will post a follow up shortly. In short, yes, installing the shaft from the top is what led to this issue. I had originally installed the shaft from the bottom (as the oil pump was going in), but it fell through the top, as a previous rebuilder had ground the ears off the shaft (without me realizing it). It wasn't until the engine was back together and installed in the car that I realized that the shaft is supposed to have "retaining ears" to keep it from falling out!

Resolution

Hi all,

The oil pressure issue turned out to be due to the intermediate shaft being installed incorrectly when I went back in to prime the oil system the second time around. I had removed the intermediate shaft between priming sessions because on the first run, it was in upside-down, making it impossible to install the distributor afterwards.

I've attached a few photos, which show that the shaft was not actually making contact with the oil pump, but instead spinning right next to it. I was able to get the shaft installed correctly with the help of my endoscope and holding the shaft with a magnet on a stick. Took a while, but I got it right and was able to verify by spinning the pump by hand using my oil priming shaft, and feeling clear hydraulic resistance.

Here are the pictures in case you're not logged in:

Intermediate shaft not installed correctly
Intermediate shaft removed, showing oil pump is OK
Intermediate shaft installed correctly

As should be clear now, the moral of the story is: INSTALL THE INTERMEDIATE SHAFT BEFORE THE OIL PUMP!

I actually did try installing the intermediate shaft while installing the oil pump with the engine upside down. However, it immediately fell out, through the distributor hole, as a previous rebuilder had ground the retaining "ears" off the intermediate shaft, and I was not aware that such ears existed. It wasn't until the motor was installed in the car that I realized the shaft initially had "ears" on it to keep it from falling out, and that they had been ground off.

I guess I got lucky the first time around when I installed the intermediate shaft to prime the oil system. Second time around took about 30 minutes, using the endoscope and magnet on a stick.

But I'm just relieved I don't have to pull the motor.

Thanks for all your help! It's raining today, but I should be able to fire the motor up next weekend!

Glad you got it straightened out before you fired it up!