We have had other members report that oil pressure increases with time and temp increase after start up. I have tried to make sense of this because it is counter intuitive to my understanding and experience that viscosity decreases with temp and hence pressure should also decrease. One factor that keeps coming to mind is the nature of the oil pump intake. The "bottleneck" is the 1/8" NPT 90 degree street ell coming right off the oil pump. Since that fitting is a casting, it's cross sectional area is subject to the irregularities of the casting process. Even a small burr in the oil stream could have an influence on flow especially at cold temperatures. Because of the foregoing "theory" I have modified my oil pump to use a 1/4" NPT fitting. The difference in oil flow was impressive and could account for the big pressure differential I live with between start up and cruise. I live with it and enjoy the (relatively) massive flow and pressure increases as well.
What kind of motor oil do you use?
Collapse
X
-
I could have sworn I saw higher pressure with lower viscosity oil and it seemed counterintuitive to me also.
I assumed lower viscosity = lower pressure = higher flow rate but my observation (as I remember it) was opposite, pressure wise.
I don't really worry about it as I never see pressure drop below 20 or so at any time.
not sure how we could measure flow rate anywaysigpicjohn
'77 catalina 30 #783
the only way to be sure is to make sure
Comment
-
-
I Assume You Have An Electric Gauge?
Originally posted by jbsoukup View PostI could have sworn I saw higher pressure with lower viscosity oil and it seemed counterintuitive to me also.
I assumed lower viscosity = lower pressure = higher flow rate but my observation (as I remember it) was opposite, pressure wise.
TRUE GRIT
Comment
-
-
My current engine starts out high - 60 PSI - and then quickly falls to 40 as it warms up.
My last engine started out at 20 and slowly built up to 40 over 20 minutes or so.
My only thought is restrictions of some kind or a bad pump = thick oil not being pumped very well. Lack of restrictions equals the usual cold oil is thicker which gives higher pressure.
Originally posted by hanleyclifford View PostWe have had other members report that oil pressure increases with time and temp increase after start up. I have tried to make sense of this because it is counter intuitive to my understanding and experience that viscosity decreases with temp and hence pressure should also decrease. One factor that keeps coming to mind is the nature of the oil pump intake. The "bottleneck" is the 1/8" NPT 90 degree street ell coming right off the oil pump. Since that fitting is a casting, it's cross sectional area is subject to the irregularities of the casting process. Even a small burr in the oil stream could have an influence on flow especially at cold temperatures. Because of the foregoing "theory" I have modified my oil pump to use a 1/4" NPT fitting. The difference in oil flow was impressive and could account for the big pressure differential I live with between start up and cruise. I live with it and enjoy the (relatively) massive flow and pressure increases as well.Joe Della Barba
Coquina
C&C 35 MK I
Maryland USA
Comment
-
-
Originally posted by joe_db View PostMy current engine starts out high - 60 PSI - and then quickly falls to 40 as it warms up.
My last engine started out at 20 and slowly built up to 40 over 20 minutes or so.
My only thought is restrictions of some kind or a bad pump = thick oil not being pumped very well. Lack of restrictions equals the usual cold oil is thicker which gives higher pressure.
Comment
-
-
Originally posted by hanleyclifford View PostWhat's with all the dotted lines in the posts lately?
Originally posted by joe_db View PostI see them in IE but not in Firefox.@(^.^)@ Ed
1977 Pearson P-323 "Dolce Vita"
with rebuilt Atomic-4
sigpic
Comment
-
-
Originally posted by joe_db View PostMy current engine starts out high - 60 PSI - and then quickly falls to 40 as it warms up.
My last engine started out at 20 and slowly built up to 40 over 20 minutes or so.
My only thought is restrictions of some kind or a bad pump = thick oil not being pumped very well. Lack of restrictions equals the usual cold oil is thicker which gives higher pressure.
Comment
-
-
After my partial rebuild early spring 2015 & having done at least 6 serious lil system flushes, I adjusted the oil pressure bypass in because i was seeinf pressure holding at about 25 - 30 lbs. After the adjustment I saw 35-40 lbs. Then I drained my last clean oil , something cheap and common, 10-30 and filled her up with 15-40 Rotella. Did a few more odds and ends which allowed the engine to cool down and give her a start.
The start up pressure shocked me at 70lbs right off the bat. Then quickly drolped to 60. I thought I waz going tl need to adjust the.pressure down. However, after warming up the pressure dropped back to hold.between 30-40 under normal opperation .
Obviously 60-70 is way too much but Im now wondering if opperation 30 & 40 is ok.Bill
1974, Tartan 30, Unchained Melody
www.CanvasWorks.US
Comment
-
-
Mr. Bing
Here is what Don M. recommends on page 5-4 & 5-5 of the Moyer Manuel.
Dress up the seat of the regulating valve every 5 years or more often if necessary. Did you dress the seat as part of the rebuild?
Then readjust the OP to ~ 50 PSI cold idle then (more importantly) 40 PSI with the engine warmed up at your cursing RPM.
And on page 5-4: "As long as the OP at idle is ~ 1/2 the OP at normal cruise all bearings as well as the oil pump are in reasonably good condition."
Hope this helps.
TRUE GRITLast edited by JOHN COOKSON; 02-17-2016, 03:37 PM.
Comment
-
-
I replaced all the engine wiring for the 2014 season so I know that is good.
I'm thinking the only way to be sure of correct oil pressure is to install a new gauge and matching sender.
Catalina Direct has a nice oil pressure gauge which matches the fuel gauge I installed last season, but the sender is metric thread.
Will any sender work?sigpicjohn
'77 catalina 30 #783
the only way to be sure is to make sure
Comment
-
Comment