327 small journal crank. When I first put this motor together I had installed a high volume oil pump. When I fired it up oil pressure was reading in the 70-80 psi range and would go higher when the rpm was increased. When hot, it would drop back to around 25 psi which I felt was ok and running down the road between 25-3 thou rpm it would run 50 psi or so. Not liking the psi at cold startup and initial running I dropped the pan and installed a standard oil pump. I also changed from 20-50 to 10-30 Valvoline racing oil to have the zinc protection and not quite as much pressure I hoped. Well, it didn't seem to make much difference. I noticed when I was on my way home from Quincy that the oil pressure gauge had a slight deflection while running at a steady rpm on the highway, almost like it was relieving pressure in the system. I am running the old can type filter on it and the relief in it is a new GM unit. The motor has right at 7000 miles on it and I was in hope that the bearings would take a set and the oil pressure would come down a bit, but that hasn't happened. I am starting to wonder if there is some restriction somewhere in the oil p***ages. I have checked the pressure with a mechanical gauge and it read like the dash unit. Thoughts? Thanks, Dennis
True, but the fact that it wants to peg the 100 psi gauge when I first fire it up is concerning to me.
The byp*** valve in the pump is what should be controlling that, I think. I usually only see around 80 on the one I have that has a gage that reads that high, but I run 5W30
I don't know exactly what "put together" means in this case, but I had a high buck rebuild done on the 327 out of my Corvette. The rebuilder, who did an excellent job otherwise, for some reason installed an Mellings Hi-Volume, Hi-Pressure oil pump. My engine pegged the 60 lb. oil pressure gauge all the time; hot idle going and down the road; constantly. I ended up pulling the pan and replacing it with a standard pump. This brought everything back to normal; idle at 25 psi and 45 psi down the road. In the interim, for some reason, the oil seals on the valve guides were also compromised, and the car began using a quart of oil for every two tanks of gas. I finally pulled the heads and replaced the valve guide seals with the Viton replacements, which solved the oil burning problem. Now, I have a leak someplace from having to tear down the engine twice. I'll find and fix that next spring. The bottom line here is that you should never use a Hi-Volume and/or Hi Pressure pump on a stock rebuild. The are designed for racing engines with increased clearances and will cause this kind of problems with stock specification engines. A curious fact is that, for Mellings at least, the Hi Volume/Hi Pressure pumps are quite a bit cheaper than stock spec pumps. Some rebuilders will use this fact to be able to tell their customers that they installed a "racing pump" and save a few bucks in the meantime.
You can always install a lo-po big block pump like I did with one of my builds.... It worked like a charm.... 60psi cold start and 45psi at a hot idle...
I will. Once I have an engine sealed up, I would rather have a sister working in a ***** house than take it apart again, but a man's gotta do what a man's gotta do T/O brg. needs some attention also. So much for American quality brgs. I guess.
Melting sells a spring ***ortment so you can change the pump relief pressure ,I think there's 5 different pressure ratings . The pressures you're seeing are about the same as mine ,hasn't been a problem in about 6000 miles
The relief valve in the filter base is actually a by-p*** valve that would open if the filter becomes plugged. Like Squirel said, the pressure relief valve is in the pump housing. It normally relieves at around 85 psi. The old 350 in my truck will run to the relief setting in cold weather at start up. It even goes above 85 if it's really cold. Hot idle it has around 15 -20 psi and runs about 45 psi at speeds above maybe 30 mph. Your setup looks like it is right on the money. I wouldn't worry about 100 psi for a minute or so on a cold engine. As long as you aren't blowing the seal out of the oil filter, I'd just run it.
Wife's 55 has a small journal 327. It runs about 75 on startup and about 25-30 at idle and warm. Runs about 55+ at 25-2800. It has 10-30 oil as well. Has been this way for many years-no issues.
I have been thinking about going to a spin on filter, but worried about the gasket holding the pressure with it being so high.
IMHO........."more-is-better" should NOT apply to oil pumps. Like stated above.......If you ain't rac'in there's no need for some "Hi zoot/racing/hi press/high vol. oil pump. Use a stock Shivel-lay oil pump pressure and spend the extra money on a big cam or something!!! 6sally6
in my un educated ,misinformed opinion its way better than to low .buick has different springs for byp*** . dosent chevy have something simular ? ive always used high VOLUME oil pumps . not higher pressure . im not at all sure you have a problem . and shouldnt affect the oil usage as long as its returning to the pan .?
Did the new oil pump come with another spring? I bought a Melling standard pump recently. It shipped with a high pressure spring, the standard spring was bagged in the box. Now may not be an actual apples to apples comparison, the one I bought was a “new” design called “shark tooth “ if I recall.
No extra springs with the new standard pump. I remember YEARS ago using washers to increase the pressure. First time I have experienced pressure this high. Guess it's good I don't have a light, it would probably blow the bulb! (just kidding)
Maybe look at crankshaft end-play or connecting rod side clearance? Though I don't imagine it making that much of a difference.
My 350 in my avatar has 80 lbs at start up drops down to 50 after warm up at 70 mph runs at 70 lbs, has done this since I put the motor in 20 years ago, lots of miles lots of smiles. I wouldn’t be concerned.
Like the man said,,,,,pressure relief in pump controls high pressure . I really wouldn’t dwell on it to be honest,,,,,,it only does it at cold temp .,,,,normal after warm up . My old 440 was so tight when it was new,,,,that it literally was a bear until over 100 degrees temp . Crank and try to drive,,,,,ran awful cold . I learned to just crank and wait a couple of minutes or so to warm up . Let temp gauge come of the peg,,,,100,,,,,was great then . Oil psi was high cold too,,about 85 at idle ,,,at operating temp,,,,all was perfect . Sounds like you have a good engine,,,with good clearance. Tommy
Looks like the consensus is to let it ride. I'll just go ahead and replace the T/O brg and drive the dang thing! Thanks for the input, D
JMO. If you're wearing out a TO bearing in 7k miles , something's wrong , riding the pedal, No return spring , something ..
I always ran stock pumps in our oval track race engines. No problems, even with big pans. Did lose a Boss 351 Cleveland due to a Fram filter, though... We only use Wix filters now.
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