New SO lost some oil pressure 40psi

[jimmymac]

Really glad I found this sight ! Im about ready to pull it out and go through it! About the third time out. I bounced it off the rev limiter,7000rpm. no problem i thought next time i looked at my oil presure it was only 40psi @2500 not the same as before. It will get 40 around 1500rpm If i rev it the gauge will bounce to 44 for half a second or so then back to 40 no matter what rpm! I pulled the oil pan tested the pump 85psi. put it back. Put some oil to it spun it ele. drill cold oil 55psi 1500rpm=3000motor right? but it never did have a lot of resistance. Pulled #4 main looks new mic.ok .003 clearance. Pulled a rod cap still looks good! Pulled intake,thought maybe a lifter galley plug had been left out or something. OH rods have .003 also. well no gushing oil anywhere escept a good even stream from all the rods and mains. I had no idea how much oil that speedpro pump moves. Castrol 10w40 oil two ph8a filters and oil cooler if it were plumed wrong it wouldnt flow right. Im sure its correct. I pulled the remote adp. on the block hoping to find a blown gasket ,wrong.It was ok. oil relief valve moved ok. How much tension does this spring supposed to have? I can move it with sm. screwdriver easily. Im not sure its 36years old! Could it have stuck open when hot then closed later? Ive been told Rotella oil sound like a good idea? Any experience with this Problem!!!! Any thoughts what could be happening here. This system worked very well in my 63 block. Should I keep the relif valve in the rear? Any help or ideas would be greatly apprecated. jimmymac

[rblong]

Gauge correct?

[jimmymac]

Both of them

[1NCE BITN]

Yeah check your gauge as rblong stated. Ground to metal and take the ignition side to battery and make sure it sweeps/pegs the full way.

Then cross reference w/ another gauge if you have one, I always keep a good generic/cheap sundial etc. on the shelf for my jeep cj-7. Next thing is to check your oil pressure sending unit! That way you backtracked to the source then your @ the motor! Hope this helps!!

[jimmymac]

two mechanical instrument cluster for fun

[Goober]

I guess you have an electric oil pressure guage. Never liked electric sending units for any pressure/temp readings. I rebulid old gauges and sending units are pretty inaccurate. It's all about ohms/restistance. I would use a cheap direct reading gauge and check your numbers before zipping the motor apart.

Just my 2 cents

Mark

[Rick Parker]

Check your filters.

[Carnut427]

Originally Posted by jimmymac

...oil relief valve moved ok. How much tension does this spring supposed to have? I can move it with sm. screwdriver easily. Im not sure its 36years old! Could it have stuck open when hot then closed later? Ive been told Rotella oil sound like a good idea?...Should I keep the relif valve in the rear?...jimmymac

Do as the others have suggested first, Goober's idea is the best way IMO to check your pressure. You should feel definite resistance when turning the pump with a drill motor counterclockwise. If you don't, you probably have an internal leak (crankshaft crossdrill plug if using a steel 427 crank has happened before). The relief valve spring won't go bad in a case like this unless it breaks, but that's not likely and visible if it does.
The relief valve in the back can be adjusted with thin washers (I use brass) to increase the pressure. Put them between the spring and the valve, the valve goes in last with the small stem sticking out.
Double check the pressure you have now first; if it's low, check for a leak somewhere. The info on the pressure relief is just FYI.
Rotella oil (diesel, also has SJ(?) automotive classification), available at Wal Mart, has more zddp ("zinc") additive for antiwear properties than today's automotive oils, is recommended, especially for flat-tappet cams, but won't cure a problem like yours.
Dan

[Cracker]

You could have spun a bearing and thus are losing oil pressure. As Rick said, check your filter for evidence.

[Rick Parker]

There was also an individual on the site a few months ago that lost an internal snap ring (sized incorectly) that allowed a plug to come out of the crank, creating a HUGE internal leak.

[CJ428CJ]

See this site: http://www.erareplicas.com/427man/engine/oilpress.htm

Not sure if this might be your problem because you indicate that you have a side oiler and this problem seems to be directed at center oilers but it can't hurt to check.

Chris

[SCOBRAC]

Thanks Rick,

I thought my snap ring drama was long forgotten. Indeed I had one of the access plugs pop out of my crank. My plug was in my pan or it would have been a very curious leak. It's possible yours is simply partially unseated. I am looking for the thread on the problem but it seems to be missing.

I didn't have any particular symptoms prior and I "got on it" one day, not near 7,000 but my oil pressure dropped from 75-85 to about 35 at speed. I drove it home (probably a bad idea) I kept the pressure up by keeping the rpm's up over 1500. The pressure looked like it would have crashed under 1500.

Long story short I found a .875" freeze plug in my pan. It looked like the guy prepping the crank used .750" internal snap rings instread of the .875" units. I ended up replacing several plugs which looked like they had moved slightly and all the internal snap rings. All of this was done with simple hand tools and a brass mallet, snap ring pliers. The plugs are just 7/8" freeze plugs and the clips I wound up getting at Home Depot. There are better spiral lock type clips out there but of all the OEM style clips I looked at Home Depot had the strongest. Total cost for parts was like $7. and a couple of oil pan gaskets.

Good Luck!

[jimmymac]

Thanks but I didnt tell you its a 428 crank Crankshaft Specialites Chromed mallory balanced std. std. with FM race berrings. If these engines get cracks are they between the mains an cam journals?