Big block 440 suddenly lost 30 PSI oil pressure.

[Banjobird]

New member so bear with me as I learn this tech stuff. Just finish 1968 Road Runner tribute car with a well built 440 stroker. Everything new and short block was machine shop built. Mellings oil pump, Milidon 6 qt pan with matching pickup tube. Built as strong street motor. Had 70 psi oil pressure from new and never less then 40 psi hot at idle. Approx 150 street miles and 3 car shows. One day coming back from a drive, oil pressure dropped to 10 psi at idle. Now never more than 40 psi at speed. Oil is full, installed second mechanical gauge to confirm accuracy, cut filter open and no metal and oil is clean. Removed oil pump and no scoring, etc, spring is good and piston moves free and not stuck, o-rings good. Removed pan and ran oil pump with drill and sound of large leak coming from upper rear of motor. Ran smoothly with no miss, tick or knock. Where is my internal leak? Sounds like a plug blown out somewhere.

 

[Dennis H]

Sounds like you are checking the right stuff. Be sure to let us know when you get to the other side on this so we can learn. Good luck. Some may say that 10 and 40 is acceptable.

A misplaced blue towel got involved with the pickup tube on mine after a valve guide seal job. It rattled like hell right away. Got off easy with bent rods. 20k miles ago. I credit the 10-40 Amsoil for saving the motor.

 

[Banjobird]

Sounds like you are checking the right stuff. Be sure to let us know when you get to the other side on this so we can learn. Good luck.

A misplaced blue towel got involved with the pickup tube on mine after a valve guide seal job. It rattled like hell right away. Got off easy with bent rods. 20k miles ago.

I have talked to several Mopar guys in my area and heard all the stories about "strange" causes for failure but all has checked out on this motor and tube and all is clean.

 

[PurpleBeeper]

1. Upper rear of motor "might" be a cam valley plug (either side of cam, back of block & squeezed between transmission & engine). However, get another opinion from someone more knowledgeable before you go pulling (or sliding back with automatic) the transmission. It's a big job & I would expect them to leak oil.
2. If the pan is already off, I might want to look at the main & rod bearings and re-torque them in the same spot/orientation as before. God forbid, there's a chance a rod wasn't just perfect or something, but I would expect a "rod knock" if that happened.

 

[oldbee]

No external leak evident I guess. WAG- rear main problem or popped endcap on rocker shaft.

 

[PurpleBeeper]

No external leak evident I guess. WAG- rear main problem or popped endcap on rocker shaft.

Hadn't thought of the rocker shaft end cap...that makes sense too...pretty easy to take the valve covers off & look if you've come this far.

 

[Banjobird]

Hadn't thought of the rocker shaft end cap...that makes sense too...pretty easy to take the valve covers off & look if you've come this far.

No external leaks or oil dripping from torque convertor housing if plug on rear of block was out. Before removing pan, I also ran engine with each side valve cover off and no bent push rods or excess oil from valve train/rocker shafts. Running 440 Source roller rockers.

 

[mopar 3 B]

Front lifter galley plugs one on each side. If loose and leaking would cause a drop in oil pressure with no external leak. The timing cover will have to be removed to check them.
Have you consulted the builder?

 

[cryplydog]

Could be possible to spin out the 4th cam bearing therefore opening a major bleed.

 

[mopar 3 B]

Could be possible to spin out the 4th cam bearing therefore opening a major bleed.

Possible but not likely.

 

[bm02tj]

Check relief on oil pump could be stuck open

 

[miller]

Another possible...crack in the pickup tube.

 

[Banjobird]

Front lifter galley plugs one on each side. If loose and leaking would cause a drop in oil pressure with no external leak. The timing cover will have to be removed to check them.
Have you consulted the builder?

Yes, builder said cut open filter to check for metal from spun cam bearing. Filter was ok. Also said to pull oil pump and ck for broken o-ring on top of housing that would pull air. 0-ring good. With pan removed, oil is not coming from front cover area, it is gushing down from above the rear main bearing. Running oil pump with drill.

 

[Banjobird]

Check relief on oil pump could be stuck open

oil pump relief is free and not scored.

 

[Banjobird]

Could be possible to spin out the 4th cam bearing therefore opening a major bleed.

That is the area where major oil leak is coming from. Would it do this after 150 miles of normal driving though? Cam was well lubed when installed, engine break-in on dyno and running Joe Gibbs break-in oil.

 

[miller]

#4 cam bearing...if it has spun, looking at your rocker arms, they would not get oil. The two oil ports, one for each side, are fed oil through the #4 cam bearing...as long as the bearing holes are lined up.
If you have the oil pan off, look over the pickup tube, to see if there's any cracks, or if it's loose.

 

[oldbee]

Cracked lifter bore?

 

[Banjobird]

#4 cam bearing...if it has spun, looking at your rocker arms, they would not get oil. The two oil ports, one for each side, are fed oil through the #4 cam bearing...as long as the bearing holes are lined up.
If you have the oil pan off, look over the pickup tube, to see if there's any cracks, or if it's loose.

Pickup tube is perfect and tight.

 

[mopar 3 B]

It's a 440 not that hard to pull the intake for a good view from the top.

 

[PurpleBeeper]

Wow, all you guys impress me with your good responses! I'm trying to think what would gush oil above the #5 main bearing and I've got nothing. I've never run the oil pump with a drill & no oil pan before. How are you oiling the motor while you spin it over with the drill???

1. Geez... I'd still check all the bearings, but I would expect some type of knock if I spun one.
2. I hadn't thought about the cracked lifter bore idea, but that would make sense.
3. Miller's idea about the #4 cam bearing might make sense for a loss of oil pressure, but you'd have to re-install the pan & fire it up full of oil (or look for bad rocker damage & again I'd expect at least a "tick")
4. 3B makes some good points.

Wow, that's a tough one