[lg1969]

I got a real problem with my 406sbc, My oil pressure was reading very low as the engine warmed up. It would drop to 10psi at idle and reaches to about 45-50 psi at 3000 when I should be reading 65psi. I replaced the oil pump with a new Milodon high pressure, high volume oil pump to see if it get better. I primed the oil pump then started the engine. Well, it did'nt work out. The oil pressure start to build up but it was struggling for the first 15-20 seconds of running the engine. When it reached about 60psi the oil pressure started to drop down to 0psi. I pulled the engine out to see what happened. I drained the oil found some tiny amount of metal filings in the oil. I removed the oil pan and found nothing.
I removed the new oil pump took it apart and impellers were in perfect condition. I removed the main bearing caps and connecting rod caps and found nothing, no scoaring marks or showing any copper. What could cause the oil pressure to go down to 0. My oil pressure gauge works fine because I have an oil light connected and now it stays on when I started the engine for a few seconds. Anybody have any idea what is causing this problem. Thanks
BTW: Distributor and drive shaft are fine, no damage.

 

[onovakind67]

Nothing really wrong with 10# at idle. My 406 runs 10# at idle all the time, has done this for years. 45# at 3Krpm is just fine, also.

 

[lg1969]

It should be reading around 30-35psi at ldle.

 

[Green-cars-live-forever]

10 lbs for every 1,000 rpm with a minimum of 7psi at idle

 

[Mike]

You might check the clearance of the pickup to pan.
Most HV pumps are 3/8" longer than the standard and that puts the pickup too close to the pan.
I use 3/8" to 1/2" pickup to pan .

 

[lg1969]

I checked the oil pick up and it is at the right level and the screen is clear. I did use a dummy dis. to pump the oil with a hand drill and nothing, no oil pressure. 4 quarts of oil in the pan that pick up should be well submerged.

 

[77 cruiser]

How about the plugs in the front, behind the timing chain?

 

[lg1969]

Look like I have to strip the 406 down.

 

[oldtimr]

Does the oil pump by itself move oil? In other words with the oil filter removed will it blow oil out the filter base when you hit the drill motor on your priming tool?

Reason I ask is because I had a 10552-C with anti-cav grooves lose its prime on me on the stand. Made pressure once for a prelube then I drained the hoses to my remote filter to fix a leak and it wouldn't pick back up.

I use a gutted distributor for a primer. You are aware there are "priming tools" that really ain't?(don't seal the annulus at the rear cam brg). You seem savvy enough I bet you have the right tool. yeah, re-read you and you are using a dist.

yeah if it was mine and had squat for pressure it would get strewed but if it had 60 with the new pump for a second then dwindled to Zero my nickel says you have a pickup that isn't sealing or a pump that lost prime.

 

[lg1969]

I'm going to try something. I'm getting a large drip pan and place it under the engine. Reassemble the oil pump and reinstall the main and rod caps, then get a small can full of oil. Put the can in the pick up then prime the oil pump with the hand drill and see where the oil is escaping.

 

[Mike]

Been trying to find you a pic of what I'm about to ask as it's easier to grasp that way -found one.
There's a plug under the rear main cap that's sometimes removed but not replaced when the block is tanked.
Is it there?
http://books.google.com/books?id=GU...esult&ct=result&resnum=4#v=onepage&q=&f=false
Scroll down to 'don't forget the plug'.

 

[lg1969]

Don't know, I have to check on that

 

[camcojb]

what are your bearing clearances?

Jody

 

[oldtimr]

I have also seen the gallery plugs behind the cam gear pop out. THAT causes instant Zero.

FYI For your test you are going to conduct....You have to position the crank to get oil to the rod journals. Their ports are 'timed' off the mains....when the hole in the main journal is pointing at the lower main the rod fed by it is NOT supplied. The oil passage must point into the upper main for oil to flow to the rods.

 

[lg1969]

what are your bearing clearances?

Jody

I have to get plastic gauge to check the rod and main. It's getting late over here. I'll keep you posted.

 

[Tom Mobley]

that plug under the rear main cap bolt won't lower your oil pressure if it's missing or goofed up some way. What you have in that case is is no oil filter. all the oil goes straight from the oil passage to the filter to oil passage returning from the filter, eliminating the filter from the circuit.

Good idea on the bucket and primer deal, but look at the three behind the upper timing gear first, might save a little time.

Rear main cap tight? Pump tight on the cap?

either end of the pump driveshaft beat up like it may have been slipping due to poor engagement?

Not a Fram filter is it?

 

[77 cruiser]

Pump could be hanging up on the dowels in the cap?

 

[Busted Knuckles]

FYI For your test you are going to conduct....You have to position the crank to get oil to the rod journals. Their ports are 'timed' off the mains....when the hole in the main journal is pointing at the lower main the rod fed by it is NOT supplied. The oil passage must point into the upper main for oil to flow to the rods.

You'll actually have to turn the engine over slowly, they're not all aligned at the same time.

David Reher said they wanted to see what was happening in the pan at rpm's once, so they submerged the pickup in a big bucket of oil and let 'er rip. All they learned is how long it takes to clean 5 gallons of oil off the dyno room walls.

Yours does sound like a good idea, but use two people - 1 to hold the turning drill and the other to turn the engine over slowly by hand to watch what's happening.
Question is, once you see oil hemorrhaging all over the place, how are you going to know what's "too much"???

 

[blumont]

This may not apply here but A friend of mine had a similar problem with oil pressure a while back. Everything seemed to check out . Finally with the engine on a stand we submerged the pickup in a pan of oil and used the priming tool to find out where all the oil was going. As soon as we started priming oil was pouring out the bottom end. Turns out the rear cam bearing was not installed in far enough leaving the oil passage partly uncovered. We borrowed a cam bearing install tool and drove it in deeper. Problem solved.

 

[lg1969]

Good morning to you all ..... Jerry, I got a funny feeling you may hit it right. Later this afternoon I'm going to an automotive store pick up a large drip pan and plastic gauge to check the main and rod bearings. I hope this problem will be solved.
BTW Tom, I'm using a Fram HP4. I've used it in the past. Used it on my 307 and 355 and had no problem. I got 35psi at idle and 65psi cruising around 85psi when starting the engine cold.