Another oil pressure problem

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Airfix

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Cloverdale BC Canada
Freshly rebuilt 340, not by me, 300 miles on it.
Running 20/50 oil, 65 psi at idle cold, warm up and it drops to 10-12 psi.
Rev to 3000 and 40 psi, pressure goes up with RPM.
If I rev it up and then release the gas pedal pressure momentarily jumps about 5 psi so from 40 to 45 then drops down as engine speed decreases to idle.
Tried new Mopar filter, checked the oil gallery plugs as detailed in previous threads, behind filter adapter, under distributor and above the rear main cap using a rod through the oil pressure port.
This engine was built by a reputable engine builder but unable to contact him.
I am suspecting a weak oil pump, no idea if it was replaced but I would assume it was.
Going to pull the pan and pump this weekend, Any other ideas?
No engine noises, no lifter clicking, have also tried second and third direct reading oil pressure gauges and got the same numbers.
 
To me sounds like a bearing issue good oil pressure cold then fades away did they replace the cam bearings possibly wrong cam journal size. I have run into where they used the wrong cam bearings had the same issue toasted a motor also check main bearing use plastic gauge to check clearences you might have to pull cam but at least check main clearences and try a new pump or give the motor back and tell them to figure it out
 
i have the same with my mild done up 360..i have about 10000km on it now,and about 20 runs ...won't change,still runs great
 
Some points to consider... an engines oil is measured by pound per square in rather than gallons per minute which simplifies the gauging. Pressure readings on a flowing system can be misleading since its actually back pressure your seeing. You probably have plenty of flow or wash within the engine at all times. FYI it only takes 7 to 9 PSI to tur off an oil light. Guages are nice if long as they dont worry you to death. A warning light is better in that respect.
Any particular reason you run 20-50 rather than 10-30 ?
 
I bet he "would" be seeing a light with 10w/30. Hot. It would be an interesting test, anyways....
 
Have always run 20/50 in my old cars, no real reason, just habit I guess as I do run 5-30 in my newer cars.
You are right about the gauge, if it wasn't there probably wouldn't be concerned, put it in to compare to the crappy rally dash one.
Also following other threads most people claim to have 35 psi at idle, although it sounds high to me as me and my sons 95 Z28's have only around 10 psi at idle as well.
Can't go back to the engine builder as i bought the car as an unfinished project, it was rebuilt about 3 years ago in WA state.
 
id start looking at the stuff you can do without pulling the motor totally apart. pull the drain plug out and see if the pickup is too close to the pan. then pull the pan and look if the pump has any cracks or if the bolts are loose. while you have it off you can check other stuff along the way like metal in the pan or pulling the rear main cap and check that the oil plug underneath is in place and snug.
 
Oil pump was severely scored, looked like someone dragged a file all over the rotor, filings in the pan. Pulled #2 and #3 main bearing cap, crank is scored bearings are toast.
All this in 350 miles, don't know what was left in the engine at rebuild but it doesn't look good.
I'm pulling ot on Sunday.
 
Had that happen to me also. Nothing like a good *******. It sure makes you feel good and have lots of trust in others.
 
I have tha happen also and now I take fior granted the mechanicals are toast and pay accordingly.
 
Pulled the engine and removed the crank, it's toast every journal, 4 mains and 8 rods are ruined beyond repair, will be looking for a new crank tomorrow. The toasted one is 0.010" undersize, block is good no problem.
The high volume oil pump is scored and just like it if it had been filed.
Could a high volume pump empty the pan and starve the bottom end and ruin the pump?
Anybody had this happen to them.
Cylinder bores look good real smooth, cam looks good but not yet removed, never had any lifter noise. All the bottom bearing were down to the copper color and some even have black patches like theyv'e overheated.
Will be checking the bottom end oil galleries tomorrow.
All this in 350 miles, I bet it probably happened within an hour the first start.
 
Yeah that's a bummer man...

As for the High Volume pump, its possible to empty the pan, but unlikely, and only at high RPM. With a High Volume, you have to run full, all the time, and its even recommended to add in a windage tray, and put in 5 quarts. Though, thats just what "some guys" say on this site.

Really though, if its all built proper and within tolerances, the stock pump runs great, at 35-45psi generally and shouldnt cause any issues.

Most of the low oil pressure problems come from cam bearings installed, improperly, bad oil pumps, or missing oiling plugs here and there.

Beware any machine shop you go to, and I do mean ANY. Make sure you find a reputable source to rebuild the engine if you don't do it yourself.

Most machine shops build fords and chevys mostly, and leave out specific mopar plugs, or install cam bearings wrong and block oiling holes.

Seen it happen numerous times, and it's bound to happen again.
 
I used to hear that a stock pan isn't capable of keeping up with a high volume pump and would empty the pan. In fact I thought that was what happened to mine a couple yrs. back. But now after much research in the subject it doesn't appear it could happen. I read an article in a book by Jim Scylzagi (I probably spelled that wrong) about how Chrysler back in the 60's did a test with a stock pump and found the inlet tube wasn't actually capable of flowing enough oil to ever allow that to happen. They said the stock pickup tube should always be replaced with a high flow unit for a perf. application.

The engine I got with my Cuda that was all rebuilt did the same thing as yours except mine even spun a rod bearing. When I took it apart it was a mess so I went through everything and found that 5 of the rods were as much as .005 out of round so I'm sure that's what let the bearing spin and trash everything. I rebuilt it and used a new oil pump with an aftermarket pickup tube and the stock pan and it's been over 2,000 hard miles and has never emptied the pan even when I've ran it up past 120 with 3.73 gears which is well over 6,500 rpm.

It's always hard to tell exactly what happened when you didn't see the engine inside before it went together. I've seen guys put new bearings on cranks that were pure garbage. Also seen guys put new pistons in cylinders with .008 clearance (mine was).
 
The bearings are 0.010 undersize, I am now thinking it could have been built too tight, I know it was real had to turn when I primed it before I fired it up and I did have the spark plugs removed so I wasn't fighting compression.
I was surprised to find journals so bad, 1 or 2 maybe but all of them certainly points to a poor build.
 
Sounds like whoever ground the crank didn't do it right and things being so tight trashed it. I had a crank turned for a 454 pulling engine I was building for a buddy and when I installed it and checked the clearance it was barely .001 on the rods and the mains were only .0015. WAAAYYY too tight for a perf. engine. Good thing I checked it or it wouldn't have lasted long.

BTW: Make sure and check those rods for roundness. 95% of the ones I see need re-sized.
 
i trust my machine shop guy but no matter how much i trust him i still check. i think we all have had some issue at one time or another when it comes to building a motor, trans, etc. after you get it all back buy some plasti-gauge and check it out. any questions and we will gladly help.
 
Thanks Camd64, dropped the crank off at the shop today, I don't think it's salvageable but they are going to measure it and see if it can be done.
All my oil gallery plugs were all there so it should have got oil, still really don't have a real answer why it happened, i need to check everyting to make sure it doesn't happen again.
 
Just finished assembling the engine, primed the oil system and lots of oil to the left rocker shaft and none to the right, turned engine over several turns by hand (I know cam goes 1/2 speed) still no oil to right rocker shaft.
If somebody has one of those Mopar performance books with the oil system schematic I'd be interested in your theories.
All oil gallery plugs were installed including the 2 at the front behind the cam gear.
I'm paranoid about this thing and don't want to install it until I'm happy.
As far as I know the head gasketscan't block the oil supply to the rockers can they?
The right rocker is supposed to get it's oil from the 2nd to rear hold down bolt area.
All ideas welcome, if youv'e got an engine sitting on a stand perhaps you could try yours.
Many thanks.
 
The cam has to be in just exactly the right position to direct oil to the right bank. Same goes for the left so you must have got lucky and hit it right the first time. I wish I could tell you where the engine has to be turned to align the oil holes in the cam to the right bank but I don't know. Try having a buddy turn the engine over real slow while you run the primer. You should be able to hit it eventually.

The only other thing it could be is whoever installed the cam bearings did the next to the last one wrong by not aligning the oil holes.
 
The head gaskets can't block the holes as long as their gaskets for an LA engine. Magnum's oil through the pushrod so they don't have the oil hole in the head gasket.
 
I pulled the cam and found the bearing was aligned correctly, pulled the head and the oil supply from the cam bearing up to the head was plugged with compacted sand.
There are signs of corrosion on the block and it had been sandblasted previously.
Removed all traces of the sand and full oil flow to the rockers.
The engine was obviously not cleaned properly at the rebuild only 350 miles before. this explains the ruined oil pump, main, rod and cam bearings.
Anyway after a crank grind and all new bearings along with a proper cleaning it's back in the car. I used a standard oil pump, oil pressure now 62 at anything above 1500 rpm and at cold start.
Hot idle is 30-35 psi.
Got 50 miles on it, changed tehe oil and cut open the filter, no sand.
I won't say it's good until 500 miles but looks like it's going to be o.k.
Thanks for all previous sugestions.
 
Man that sucks when people screw things up like that. The engine I got with my Cuda was supposedly rebuilt and it was a screwed up mess too.
 
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