360 engine sudden drop of oil pressure while cruising at 3200 rpm

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chasonmarose

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so I was cruising today on the highway and I heard a thump I looked at my gauges and my oil pressure dropped right to zero!! Shut it off and towed it home, I pulled the dizzy and the rod and gear that runs into the oil pump to see if that had broken and it is not, this motor is rebuilt with around 430 hp, 10000 km on rebuild about, now when it was rebuilt there was no excessive clearances or anything at cold around 2500 rpm I would get 38 psi when warm Arne that range 20 psi make psi I would get when warm up to 5500 rpm is 28 psi at idle 950 rpm I would get 3 psi, this was a milidon high volume pump, I am wondering if the clunk I heard was the pickup falling out of the pump as they are just press fit, but I would expect to get at least 70-80 psi cold start and around 30-40 hot and around at least 15 idle... Any help would be appreciated.. Gonna drop pan tomorrow and see what the damage is


Chase
 
5 will get you 10 the oil pump female hex drive is stripped.
 
Serious help please, I hope this is an easy fix cause it's not in the financial department to be doing a overhaul again
 
Serious help please, I hope this is an easy fix cause it's not in the financial department to be doing a overhaul again

SO who was not bein serious? You've never heard the saying "5 will get you 10"? You cannot be serious. You cannot figure it out? 5 will get you 10 = a 50% chance. Come on man. You gotta have more sense than that. Pretty high probability the female drive hex is stripped. You said the drive shaft is good.....or not broken was what you said. Did you look at the end? Is it rounded off? If not, my guess is the oil pump locked up and stripped the female hex out. I have actually seen that a lot lately. I think it's because of cheap imported parts. If everything you pulled out "looks good" as you say, then "the problem" must be down below. 'Taint but one thing left and that's the oil pump.
 
Why not try to spin the oil pump with a priming shaft?

remove the distributor and distributor drive gear and try to spin the pump with a priming shaft on a drill and see if you can develop pressure...

Check the bottom of the distributor drive gear for any signs of the hex getting chewed up, if not, then check the oil pump and pick-up tube. Is the pick-up tube in tact? Is the oil pump seating properly on the main bearing cap, or is there a gap?
 
first make sure your oil pressure gauge is worth two *****


drop the pan change the pump and drop in a new distributor drive gear , proceed to prime it , then start drive and enjoy . hows that for serious lol
 
Hard to understand the details of the OP. However, a typical rebuild will have 70-80 psi cold, then when hot drop down to 20-30psi at idle and about 60psi at full output which seems to be 2500 or so and up.
 
HI volume oil pump strikes again :banghead:

Anyone with half a brain would know if you install a high volume pump you need the hardened intermediate shaft....and it says so in the MP engine manual so you know it is right.:glasses7:
 
first make sure your oil pressure gauge is worth two *****


drop the pan change the pump and drop in a new distributor drive gear , proceed to prime it , then start drive and enjoy . hows that for serious lol


Right to the point.... :cheers:
 
"C'mon man, you gotta have more sense than that"
"Anyone with half a brain"
Canadians have sayings we don't understand.
I thought we were here to help one another, not criticize!
We're a great resource. We are better than that.
We learn by our mistakes and pass it on.
Isn't that how it works?
 
It could be the cotter pin in the oil pump pressure relief. I've had them deform or even shear resulting in lowered or no oil pressure. Easy enough to spot and repair (with a larger pin) when you get the pan off. My experiences occurred with the MP high volume oil pump.
 
The one consistent thought through all this is it's not likely to be a fix from up top. You are going to have to 'dig' into the engine to find out. What was suggested was just troubleshooting methods to better locate what actually is going on. Again, bottom line is YOU are going to have to pull that engine and tear into it to fix it. Maybe not right away, but eventually you will have to. At least that's what I would do.
 
so I was cruising today on the highway and I heard a thump I looked at my gauges and my oil pressure dropped right to zero!! Shut it off and towed it home, I pulled the dizzy and the rod and gear that runs into the oil pump to see if that had broken and it is not, this motor is rebuilt with around 430 hp, 10000 km on rebuild about, now when it was rebuilt there was no excessive clearances or anything at cold around 2500 rpm I would get 38 psi when warm Arne that range 20 psi make psi I would get when warm up to 5500 rpm is 28 psi at idle 950 rpm I would get 3 psi, this was a milidon high volume pump, I am wondering if the clunk I heard was the pickup falling out of the pump as they are just press fit, but I would expect to get at least 70-80 psi cold start and around 30-40 hot and around at least 15 idle... Any help would be appreciated.. Gonna drop pan tomorrow and see what the damage is


Chase

A little test,

A}First, add about 3 or 4 Quarts of Oil.

B} Then start the Engine for a short run, and see if you can get any movement
in oil pressure.

C} If you do, then it is a Pick-Up related issue.
 
About the only thing that could make an loud enough 'thump' sound is a pushrod bending/jumping of a lifter and the lifter jumps its bore as the cam knocks it out, creating a big internal oil leak.

I would pull the valvecovers first and check for a very loose rocker.
(The engine should've felt like it ran on 7 cylinders right after this had happened)
 
Why not try to spin the oil pump with a priming shaft?

remove the distributor and distributor drive gear and try to spin the pump with a priming shaft on a drill and see if you can develop pressure...

^
What he said. Cheapest, fastest, and easiest thing to diagnose and eliminate FIRST before tearing everything else apart.

It's no guarantee that the OP won't have to tear apart something in the end, but it's an easy test that can yield information about oil pump health before going through the effort of dropping the pan.

-Kurt
 
Another thought - Make sure you didn't blow the gasket on the oil filter. I had a high volume pump once develop enough pressure to bulge the oil filter away from the block, breaking the gasket seal. In my case it blew oil all over the engine compartment and made a big mess. :)
 
Big block mopar you were right pushrod snapped metal fatigue, and was missing an oil gallery plug in front of distributor, motor is good now lots of pressure 80 cold 35 idle 60 cruise speed
 
Big block mopar you were right pushrod snapped metal fatigue, and was missing an oil gallery plug in front of distributor, motor is good now lots of pressure 80 cold 35 idle 60 cruise speed
Congrats on the fix! Just curious. How does an oil gallery plug get removed and not replaced? I don't even understand why it would have been removed in the first place. Seems out of the norm.
 
Congrats on the fix! Just curious. How does an oil gallery plug get removed and not replaced? I don't even understand why it would have been removed in the first place. Seems out of the norm.


Not at all if you hot tank a block.
 
Not at all if you hot tank a block.

Got it. : ) I've had several blocks hot tanked and never knew for sure whether all plugs were removed. They were all installed when I picked up the block. Something I will look for in the future. Thanks.
 
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