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Google "Tunnel Ram 406"
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Discussion Starter · #1 ·
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 when it should be reading 30-35psi. 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. :confused: 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.
 

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lg1969 said:
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 when it should be reading 30-35psi. 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. :confused: 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.
What kind of oil filter?
Do you have your bypass plugged?
 

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Google "Tunnel Ram 406"
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Discussion Starter · #6 · (Edited)
Fram HP-4. I did not plug the bypass plug. The funny thing about the filing in the oil pan was only enough to fill a not even a thimble. I use a dummy dis. to pump the oil pump. The drill is spinning at around 2000 RPM and nothing.
I should mention the pick up is at the right level and 4 quarts of oil the pick up is well submerged.
 

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I wouldn't sweat the filings. I've seen peoples motors with "filings" in them which turned out to be just silver looking material that was from ARP assembly lube and others, lots of people make that mistake.
I would, however, sweat that oil filter choice.
Throw that thing away and put a napa gold or a wix on there, and I'll bet it goes back to normal.
 

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Google "Tunnel Ram 406"
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Discussion Starter · #8 · (Edited)
I used the fram HP-4 before and never had this problem. Years ago when I had my 307sbc. I had 35psi at idle and 65psi when cruising around. I was using that filter. Maybe your right. I should try another filter. I cannot believe a filter would clog in 20 seconds.
 

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That's a $10.00 part that's easy to replace.
Do a search on here about fram filters. I'm not denying that they've worked in the past, but they do fail, and quite often. It's a simple thing to swap out and see if it fixes the problem that happens more often than you'd believe, before having to pull the engine.
I state in my warranty info that anyone that uses that brand filter voids their warranty on engines coming out of my shop.
 

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My pipes are my music
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Sounds like something is causing the pressure relief valve to stick open on your pump. When you go to Napa, ask for a good filter with an "anti drainback valve" in it.
Fram doesn't have one in the US, only in Canada. The anti drainback will keep more oil in the pump for faster oil presssure build up especially on cold mornings. Only other tip I can give you is check your oil pressure line from the engine to the gauge and look for a pinched line.
 

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lg1969 said:
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 when it should be reading 30-35psi. 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. :confused: 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.
Either an obstruction or a leak!

An obstruction can be something in the line ahead of where you tap off for the gauge. If off the back of the block:

1) The filter becomes immediately suspect. "Filings" in the oil is not a good sign, at break in there should be a metallic sheen in the oil, but not filings.

2) One that also happens is the ball check that redirects the oil thru the filter is driven too deeply and begins to obstruct the main oil galley where it is met by the short galley coming out of the filter back to the riser galley on the back of the block. This reduces pressure all the time, but is worse when the oil is cold or the RPMs high at any temperature.

Leaks can be more numerous as to source:

1) The pick up needs to be no more than a 1/4 inch (3/16s is better) off the bottom of the pan, otherwise it can and will develop a vortex in the oil and will suck air in. This will be worse with higher RPMs and better with less and will be oil temp sensitive as well bad when cold and less when hot.

2) The pickup doesn't make an air tight fit with the pump. This will be worse when the oil is cold or when the engine is operating at higher RPM.

3) The relief valve is stuck fully or partially open all the time. This will show low oil pressure all the time which it being worse when the oil is warmed.

4) Distributor not seated, this opens a leak back to the pan on the passenger side lifter galley.

5) A leaking or missing oil galley plug, there's one at each end of the three oil galleys (center main, left and right side lifter).

6) Excessive bearing clearance resulting in oil passing thru the clearance faster than the pump can replace it. This will be slow to build pressure, it will always be low but will be lower at all RPM ranges as the oil heats up.


Bogie
 

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Google "Tunnel Ram 406"
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Discussion Starter · #13 ·
oldbogie said:
Either an obstruction or a leak!

An obstruction can be something in the line ahead of where you tap off for the gauge. If off the back of the block:

1) The filter becomes immediately suspect. "Filings" in the oil is not a good sign, at break in there should be a metallic sheen in the oil, but not filings.

2) One that also happens is the ball check that redirects the oil thru the filter is driven too deeply and begins to obstruct the main oil galley where it is met by the short galley coming out of the filter back to the riser galley on the back of the block. This reduces pressure all the time, but is worse when the oil is cold or the RPMs high at any temperature.

Leaks can be more numerous as to source:

1) The pick up needs to be no more than a 1/4 inch (3/16s is better) off the bottom of the pan, otherwise it can and will develop a vortex in the oil and will suck air in. This will be worse with higher RPMs and better with less and will be oil temp sensitive as well bad when cold and less when hot.

2) The pickup doesn't make an air tight fit with the pump. This will be worse when the oil is cold or when the engine is operating at higher RPM.

3) The relief valve is stuck fully or partially open all the time. This will show low oil pressure all the time which it being worse when the oil is warmed.

4) Distributor not seated, this opens a leak back to the pan on the passenger side lifter galley.

5) A leaking or missing oil galley plug, there's one at each end of the three oil galleys (center main, left and right side lifter).

6) Excessive bearing clearance resulting in oil passing thru the clearance faster than the pump can replace it. This will be slow to build pressure, it will always be low but will be lower at all RPM ranges as the oil heats up.


Bogie
Thanks I'll take your advice and too all of you :welcome:
 

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Google "Tunnel Ram 406"
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Discussion Starter · #14 ·
I made a quick check at the rear cam bearing and what can see it look like the rear cam bearing may be out of place. Is it possible the rear cam bearing was loose to begin with and the new oil pump pushed bearing out of place because of the added volume? The old pump I was using before was a low volume, high pressure pump? The pressure was low with the old pump. It should of read 65psi but it was reading 45-50psi and 10psi at idle, when it should had read 35psi.
 

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lg1969 said:
I made a quick check at the rear cam bearing and what can see it look like the rear cam bearing may be out of place. Is it possible the rear cam bearing was loose to begin with and the new oil pump pushed bearing out of place because of the added volume? The old pump I was using before was a low volume, high pressure pump? The pressure was low with the old pump. It should of read 65psi but it was reading 45-50psi and 10psi at idle, when it should had read 35psi.
The SBC uses three different cam journal diameters, when the cam bearings are installed one needs to be sure the correct size bearings match the proper cam journal. They go #5 and #2- 2.010 inch; #4 and #3- 2.00 inch; #1- 2.02 inch. If done improperly you will have one big mess.

Bogie
 

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Another thing on the rear cam bearing. If it isn't driven far enough into the bore(driving from the front of the engine) and verified with a probe or pick that the oil hole is aligned with the annular oil groove around the bearing bore you can have an direct oil leak depending on how much of the groove is exposed beyond the rear edge of the bearing.
 

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lg1969 said:
Fram HP-4. I did not plug the bypass plug. The funny thing about the filing in the oil pan was only enough to fill a not even a thimble. I use a dummy dis. to pump the oil pump. The drill is spinning at around 2000 RPM and nothing.
I should mention the pick up is at the right level and 4 quarts of oil the pick up is well submerged.
not enough gap can cause scavenging and loose pressure .
oil bypass or filter i say not your problem , because bypass will by pass filter , still have pressure .to loose pressure with clogged filter , it have to blow out the rubber seal at block .you plug bypass , this will happen .
for it to turn bearing , not in my book unless old cam bearing before spun and wore it's placement or crack in bearing bore from removal or replacement. them suckers tight if you ever removed one .
as for chevy small block, only the first one needs the hole in right location , rest are all the same size .
oil pressure too high could blow the plug out the back where cam is .

this all my opinion , may not be others of .
be nice
 

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One has to ask, it all ran good and then, something changed. sounds like he found it. And, a stuck pressure relief valve, or broken spring behind it will cause the same problem. Good pressure when cold and then steady decline as the oil heats up. I had a problen simular to his once a 455 in my pont. suddenly started loosing pressure after it got warm. I had a vague idea what might be wrong but after a couple of weeks driving around at 25lbs. pressure
nursing back and forth to work it suddenly started running normal again.
After a few more months I Pulled the engine out and found #1 main bearing had spun all the way around 1 time and had stoped right on the money.
That pretty well explained the wierd pressure thing.
 
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