Recent build of a 79 400M

Lots of goodies, It runs solid, fires up with no issues idles beautifully and makes no ticking or knocking noises.,
But...... It has little to no oil pressure.

Tried mechanical and factory pressure senders.

It has a HV oil pump and right after the rebuild there was 65-70 psi, now when hot there is less then 5 at idle and 30 when loading the engine.
I did not know about the oil mods at the time of the build.

I have a factory OP with a moroso heavy spring to install in it, as my next attempt to ragain oil pressure

I have read about the oil feed lines from the front plug to the rearof the block, I'm on the fence with these mods?

Also i have thought of running a guage right at the pump but that will only give me a pump pressure reading not a system reading.

Whats the next move?aside from installing a 460 or scrapping this engine?

Cause next one is going to be a Tmeyer 434 for sure!

 

If you only had 5psi at idle the lifters would be ticking real bad.

Is the passage to the oil sender plugged?

 

That does sound scary. Could also be oil pump coming loose or rotor cover plate, stuck relief spring,-all of these preferable to main bearings etc crapping themselves, and I have read something/somewhere, where the pump came loose for somebody on occasion so ........
Fit gauge to the plug by the oil filter to double check and if it's still low, I would be removing the pan and checking the pump and maybe even some of the mains. If you check the pump, you can narrow it down to something else. Fitting that pump wont fix that problem unless there is something wrong with the one in it now, with the problems mentioned above. If this is the case with a new pump and spring your problems could well just disappear especially in the case of a stuck relief spring, but you may be able to see that on a tear down.

30psi is low but not that low. On a recently rebuilt engine it would be lower than I would like though.
I have used the moroso spring on a standard oil pump and at highway revs when hot it is up around the 550kpa mark-from memory- and down around the 300kpa mark at idle. Thats 80psi and 43psi approx) respectively, so happy with that.
I also dont really agree with the auxiliary line to the back of the block. I like Tim meyers mods, but I was to far gone on my build to contemplate them.
Is this engine rebuilt or have you bolted the top stuff on? Just wondering as if your cam bearinges were completely shot, this could also happen. Would expect new bearings on rebuild so just wondering?

 

Did you check the bearing clearances with a good bore gauge reading in .0001" ? Did you check all the cranks journal sizes in 2 places ? Check runout ? New cam bearings ? Did you check the cams oil clearances ? Did you check lifter fit in the block ? If the bearing clearances were checked & set there should be plenty of psi. and no reason to do any oil mods, that stuff is just for high rpm racing engines.

 

X2 with mark-a replacement oilpump will only fix a problem in an oil pump. Everything else is dictated by clearance although you did say you had decent oil pressure to start with, so hoping it is something silly with an oil pump (for example).Pity it wasn't an external oil pump-very easy to rule out.

 

Make sure your oil pressure gauge is working properly before you assume the worst.

 

Check bearing clearence. Too much give you a lot of pressure lost.

 

.. Did you ever discover the real problem? Hope it was just the gauge/sender... hook up an all mechanical gauge temporarily to be sure...

 

bump.67890

 

Thank you for all the replies, summer has been super busy, i have not ahad a chance to go further on it.
As soon as i do i will post and let you know what i find.
thank you

 

Nope, not on a 400. 5psi is quite normal for one with lots of miles.

 

If you had 30 psi at the front port, it'll be lots less at the rear. The main gallery is the right side lifter gallery. Be that as it may, I suspect you've got a bearing wear problem if the pressure was good, then fell off.

 

So, this is only years late.....but. The engine finally had no more start left in her. Tore it down after it spun the dizzy gear, clear off!. Found number 4 cam bearing walked half way out of it's nest. I pulled everything apart, kept the same bottom end, put new bearings, new cam, new lifters, new p-rods, new OP and started fresh. This time, we broke the cam in correctly. So far she runs like a dream. Now I just yearn for more power!

 

Saweet! Nothing I like better than someone coming back with thread updates. Even if it takes awhile. I hate being left hanging at the end of a thread. Glad to hear your engine is now sorted out.

 

Ya, it's awesome! These Cleveland's turn on.
​​They rev like nobody's business and with the 4" stroke, tons of torque!