Technical SBC oil pump shaft length

Here's a problem that's worn me to a nub. Done this so many times I've lost count. Searched to no avail.

350 SBC in my 56 pickup that WILL NOT get oil pressure with neither of two stock distributors, like the tang is not engaging the pump drive slot EVEN THOUGH THE DIST IS SEATED ON THE INTAKE!!! Even tried with both a stock and alum intake.

Removed the shaft from my primer dist., seated it's tang in the slot and measured length at the manifold. It's a 1/4 inch longer than either of the stock HEI dist's!! WTF!

This is a used motor I bought, and I thought that the stock HEI came out of it. Cranks fine, just no oil pressure except with the primer.

Tried every shaft alignment trick that I could think of, but this POS is wearin' me out.

How in hell could it have a short pump drive, (like Nova)? Sure don't feel like pulling the pan.

Thanks for any suggestions!

 

The chevy II was the only other length oil pump drive that I have heard of.
Any chance that you could get ahold of the shaft and yank it out don't think that plastic sleeve would cause a problem if it wasn't there.

 

Watching this one. I'm no help. But like to see what the answer is.

 

Yankin the shaft?

Don't know that I have anything that will reach it, even with the intake off.

Definitely need the retainer on the shaft, I would think.

Don't understand why the stock HEI's won't engage.

 

I have pulled apart many a small blocks that have been running with the sleeve laying in the pan. I done think the problem is with the dist.
Does the oil filter mount pad look different? The chevy II blocks have the filter mount located higher in the block.

 

Thanks, I'll check that out. This motor came out of a buddy's pickup, but wasn't original to it.

 

Will the engine run? Is the drive gear on upside down ???? If it is it wont run or line up with the camshaft.
I get them in all the time with the gear on upside down.....
Just another thought/.

 

Engine cranks and runs fine, but with no oil pressure, I haven't let it run long enough to warm up and adjust the valves, etc. Gear's on correct, on BOTH dist's.

BTW, what is the correct length of the standard oil pump shaft?

 

have pulled the shaft with a strong magnet then reinstalled witht he nylon sleeve

 

Look at the gear set up to make sure it is turning the pump in the correct direction. I'm recalling reverse set ups from the recess of my old brain. I sure as hell don't know why, but I think there was something about truck timing sets that had reversed gear drive gear sets with only two gears and no idlers. This turned the cam reverse if I remember right, and it would turn your oil pump into a blower!

Use a piece of welding rod to measure from the manifold surface to the tang on the pump shaft. Compare that to the distributer. Unlikely this is the issue, but it is what you need to know. Compare your distributor to the primer you are using. If it makes pressure with a primer, check direction of rotation of the primer and confirm that the rotor is turning the same direction wight the cap off.

 

Gonna watch this thread because of this reply. Anyone else think this possible? Love this board, alway's something around the corner when you don't expect it.

 

I see that Moroso make a shaft that is .125 shorter for a small block with a big block pump.

 

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You said it will start ,so dist. rotation has to be right.Only time I ran across this was when we had a truck block(big Block) which is taller and Hei used a longer shaft.Never heard of this on a small block. I too wish I could be more help.

 

Not sure this helps but a pump shaft from a 283 sbc is not the same length as one for a 327 sbc.....its been awhile but the 283 is a bit longer as I recall ......might want to check the casting numbers on the block

 

Are you using a electric oil pressure gauge? I used to use a sending unit mounted at the top of the block under the distributor. I'm wondering if you could be getting a connection problem when that big ol HEI gets installed. If it's an old school with an oil feed gauge, do you possibly have a kink induced by the HEI. It takes up a lot of space and might do this, especially with a synthetic line.

One more thing, is the engine showing signs of low oil presure when running? Tappet noise? Bearing knock? It wouldn't take very long to hear it with no oil pressure. You said it runs fine. I missed that initially. This is what leads me to look at the oil gauge idea.

I understand your frustration. I've had build problems that kept me up for days. I never did find a wrench I threw out of frustration one time!

Do you have any experienced guys that can come over and look things over? Tough on the ego, but a second set of eyes that isn't involved can really help see things sometimes.

 

Mechanical oil pressure gauge. Reads fine when using the primer. Connected at the rear of the block.

With intake off, I can just see the top of the pump shaft, and it looks ok.
Turned it with screwdriver and primer shaft, and checked its index so the gear would mesh and rotate to that exact spot. Dist. base and gasket seat firmly onto manifold.

Again, I've done this OVER two dozen times, with two distributors, and two manifolds.

Anybody have the correct length for the correct shaft. I've found another in my parts stash for comparison.

 

I have 3 of them and thay all are 5 3/4 inch long.

 

Thanks, Saltflats!

 

There were some oddball racing pumps that Melling made that used a different intermediate shaft. There are also tall deck blocks like the Dart small blocks that used a longer 6.25" shaft. I doubt you have the Dart block though.
It is possible that the oil pump that was in the engine previously was a special pump that had a longer shaft, so it used a shorter intermediate, and if you replaced the pump, but reused the shaft, then it might be shorter than the stock 5.75" shaft.
As firmly as the shaft snaps over the pump shaft, I doubt it can be pulled off from the top. As tough as it may be, the pan will most likely need to be pulled to determine if the pump or the shaft is incorrect length.

 

Pick up a preluber and use an electric drill to run the pump, that will tell you if you have oil pressure. Once you determine that you can start measuring the distance down to the shaft and compare that to your distributor.

But first you need to see if you truly are getting pressure or not.

Don

 

Since this is a 1956 engine, I'm curious. I just looked up a melling pump shaft, and they indicate it for 1957-1967. Some long-unused brain cell reminds me that 55-56 engines were different (flat ground spot on rear cam journal, different distributor, etc). Is there someone who specializes in the 55-56 265 engines and early 283 that could confirm this? My memory isn't what it used to be.

.bjb

 

Don, he mentioned earlier in this thread that he had already used his priming tool and got good pressure. He also measured the length and compared it to his distributor and found it's 1/4" short.

 

I just checked on a 327 from the edge of the intake end rail on the block to the top end of the pump shaft it is 6 1/8 inch.

 

Whoops, missed that.

Don

 

"Removed the shaft from my primer dist., seated it's tang in the slot and measured length at the manifold. It's a 1/4 inch longer than either of the stock HEI dist's!"

Are you saying the primer seats 1/4 inch deeper in the tang than your distributors? As in the shaft is longer than the distributer shaft? That is definitely enough to disengage the pump drive.

If you need to remove the intermediate shaft, I would look for a piece of soft metal tubing that will just not quite fit over the shaft. Try it on a shaft on the bench. Use aluminium or copper tubing. Use a file or Dremel to make a taper a bit at the opening. If you can drive the tubing over the top of the intermediate shaft for a tight fit, then you can work on lifting the shaft from the pump. The pump is pretty solid, but DON"T hammer to hard, some pumps will let the pump shaft move in the pump drive gear. Even a piece of tubing/hose with strong vacuum might lift it off the plastic retainer. Ive done this successfully. I used to replace them with a tool steel intermediate shaft and collar. I didn't like to pull the pan.

Hood would have to be off and you need fire wall clearance to do it.

 

^^^^Thanks for the advice, I'll triple check the measurements, and if they're still indicating a short shaft, I'll try pulling it out. The reason, IMO, that the primer is engaging is that with a bare shaft, it drops in further, enough (1/4") to engage the pump shaft.

 

It's been a long time but I think this is the shaft I used to use. It's been so long since I've been inside a small block. Seems to me this one won't go in from the top for some reason.

http://www.speedwaymotors.com/Moros...-Pump-Shaft-for-Big-Block-Oil-Pump,32242.html

The other question I have is, are you sure you are seeing the shaft when you look in the engine and not the top of the oil pump shaft itself? If the plastic sleeve is broken, memory says the shaft has the ability to fall out when the engine is rolled over on the engine stand. Someone else can confirm this. Ensure the distance from the bottom of the tang in the shaft to the surface of the intake is the same as the distance from the distributer tip to the bottom to the mating surface of the distributer. I'm just wondering about the possibility that your primer is able to reach all the way to the pump with out the intermediate shaft in place. Not likely but I'm really just grasping at dust in the sunlight here.

You will notice its 0352 hours, which means I'm losing sleep too, and this is what's on my mind.

Does the engine sound like it has no oil pressure?

Check to see if you are getting oil to the rockers or the sending unit. Pull off a rocker cover and Pull the power wire to the distributer so it won't fire, and crank the engine over with the starter. It will pump oil to the rockers and sending unit. This is actually how I primed engines. I felt the rotating assembly gave opportunity for all the timed oil holes and galleries to fill with oil.

I actually run a separate circuit to the starter so I could crank engines till I had oil pressure, then I would turn the key to light the engine ignition. By doing this I have bearings show almost zero wear after extreme use. But I digress.

Odd request but, post pictures of your distributer. Especially the gear end. I'm interested in looking at the groove on the housing flange.

Let us know what you find.

 

Thanks to all who have replied.
To review and consolidate for all those who offered suggestions:

1. The truck is a 56, the engine is not; just a stock 350.

2. It gets oil pressure using a drill driven, stripped down, iron body dist. with no guts and NO gear as a primer. Rockers are getting oil. With MECHANICAL GAUGE's line disconnected at the rear block port, pressure is instantaneous.

3. Two different, late model, large body HEI dists. WILL NOT produce oil pressure, both seat tight into the manifold. One presumably was original to the motor. Used two different manifolds, stock and Edelbrock.

4. The engine fires and runs. Valves need adjusting.

5. The PRIMER DIST's shaft, with no guts or gear attached, will bottom out in the drive tang, BUT measures 1/4" longer than the two fixed shafts, measured at the manifold.

6. My deduction is that the oil pump shaft is too short, as all the other dimensions are fixed and the same.

Anyone have any other suggestions, before I try pulling the pump shaft out from the top?

THANKS!

 

Does your priming dist have a stop on the top of the shaft that would control its amount of downward movement?