Boatally Insane

iTrader: (1)

Okay.. now that I FINALLY have the distributor figured out, it looks like I may have an oil pressure issue.....


The engine is 555 cid 630hp N/A

Oil pump is a high volume Melling 10778.. . Main bearing clearance is .0028" on 1-4 .0030" rear main. Rods are .0027" Lifters are .0016"
Oil pan is a Summit Racing 11 quart.. have 10 qts in it currently to make sure aeration is not occurring.
-12 oil lines Mr cool MRC CPH-775 oil cooler with the thermostat bypass tube blocked. Fram HP6 Filter CP performance "extreme" oil filter adapter ..

Had cheap STP brand 20-50 in it...(long story.. been changing oil often due to a contamination issue)

Oil temp under 140 (not reading on the gauge)
55 psi @700 RPM
67 psi @ 3000 RPM
70 psi @ 3500 RPM
65 psi @ 4000 RPM

Ran a while.. oil temp stabilized at 170 degrees...
20 psi @ 750 RPM .
55 psi @ 2000 RPM
60 psi @ 3000 RPM
57 psi @ 4000 RPM
50 psi @ 4500 RPM
50 psi @ 5000 RPM


When I bring the RPM back down from say 4500 RPM to 3000 RPM the oil pressure comes back up in 20 seconds or so...


Do I have a mechanical issue or was it maybe the cheap ass oil I was running ?


THANKS !


Doug

mike tkach

iTrader: (3)

i am sure you meant .0028 and .0030 on the main bearing clearance.try using brad penn oil and see how the pressure looks.

fbc25el

Why is the thermostat tube blocked?

ICDEDPPL

iTrader: (1)

Looks identical to my Melling 10778 pressures (with spring oilers) without spring oilers hooked up it was a bit better but not a whole lot.
I worried about it for years but never had a oil related problem.
Besides contaminant marks during assembly the bearings looked fine... (correct me if I`m wrong mike T)


Edit: noticed you have the big boy filters , I used to use Wix 51222R with a bypass.
I did some research and decided against the bypass filter. I believe it improved oil pressure at idle


https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1

Boatally Insane

iTrader: (1)

My initial test run, the oil thermostat wasn't working, allowing the oil to bypass the cooler..
5000 RPM oil pressure was 35 psi.. no idea of oil temp, didn't have the gauge installed yet but it was HOT !
So I plugged off the bypass tube to force all the oil through the cooler...

Boatally Insane

iTrader: (1)

I'll look in to that one..

So, dropping pressure at higher RPMs isn't an issue ?
Never had an engine do that before....

mike tkach

iTrader: (3)

dropping pressure at higher rpm,s is an issue,that is when you need the pressure the most.

fbc25el

Do you know the clearance from the bottom of the pan to the pickup?

mike tkach

iTrader: (3)

without a oil temp gauge how do you know if the oil is HOT?90% of the oil will bypass the cooler until the oil t stat opens sending the oil through the cooler.35 lbs oil pressure at 5000 rpm usually indicates lack of oil present at the oil pump pickup that can be caused by many reasons.

mike tkach

iTrader: (3)

to answer your question,i doubt the issue is the oil but trying another oil brand might answer that question.