Re: Small Block High Ol Pressure
Why don't you just check/repair/modify the gauge to make you happy? Lot's easier than changing pumps.
Why don't you just check/repair/modify the gauge to make you happy? Lot's easier than changing pumps.
-
-
Re: Small Block High Ol Pressure
HIGH OIL PRESSURE PROBLEM SOLVED!!! To any of you who are following this thread, I can report that I have solved the high oil pressure problem. I searched the archives and found a post in which Joe Ciaravino gave the GM partnumber 3814903 for the original 45 PSI small block oil pump relief spring. they are still available from GM so I ordered one from my local Chevy dealer and had it overnighted . The cost for the spring was about four dollars with no discount plus freight. Comparing this spring to the Melling 55 low pressure (58 psi) spring reveals the problem. There is a noticeable difference in the feel of the spring since the original GM spring uses .037 wire while the Melling spring uses .040 wire. There is a difference in the number of coils. The GM spring had 23 and the Melling had 20 active coils. The lengths were pretty much the same within reasonable manufacturing tolerance.the GM spring is noticeably softer. I installed the GM spring and low and behold my oil gauge is reading about 45 PSI at idle and not more than about 58 PSI at higher RPM. At least now I know what my pressure is , rather than having the gauge pegged all the time. I think this is a problem that a lot of us have had with our small blocks with modern engine parts. It's not necessarily a very easy fix. I have a lift and it took me about 4 to 5 hours, the way I putter around. If you have a steering damper, that has to come off, the steering linkage has to be disconnected and moved out of the way, and the starter, starter wiring and solenoid shield need to be removed.Then the oil pan has to come off followed by the bottom of the oil pump. Changing the spring is very easy to do. Just use a small drill blank and a hammer to push out the roll pin that holds in the spring. Installation of the spring is the reverse . The rubber end gaskets that came with the oil pan gasket kit that I bought from a well-known Corvette parts supplier had the wrong parts in it. There is a thin and a thick rubber gasket needed on one and of the oil pan depending on which pan you have. If you use the wrong one you'll surely be in trouble with a big oil leak. Thanks to all the posters who gave me technical help with this problem, especially Joe and Duke. Bill Gould Plymouth massComment
-
Re: Small Block High Ol Pressure
Bill------
You didn't need to search the archives for the info; see my post #2, above (the one following your original post).
As far as the oil pan gaskets go, all 1957-79 Corvettes with small block use the same side rail and rear oil pan gaskets. 1957-74 oil pans use a 0.22" thick front gasket. 1975-82 Corvettes use a 0.41" thick front gasket. Most SERVICE oil pans after about 1976 for 1956-74 Corvette small blocks use the 0.41" thick front gasket.In Appreciation of John HinckleyComment
-
Re: Small Block High Ol Pressure
I checked my '77 P&A catalog, and 3814903 is the correct original part number for '62 and up OE small blocks with the "standard" 40-45 psi hot oil pressure at 2000 spec, and these models should have 60 psi gages. It has 21 coils and a free length of 2 7/32". BTW the list price back then was $0.17.
I'm surprised it yields readings as high as you report, but unless you plan a PV, don't worry about it.
The 55-60 psi spring that was used on late '63 to '65 mechanical lifter small blocks and some later SHP small blocks is 3848911. According to the catalog it also has 21 coils, but has a white stripe of paint. Models with these engines should have 80 rather than 60 psi gages.
DukeComment
-
Re: Small Block High Ol Pressure
Yes, Joe,I missed that part number in your first post. Concerning the front rubber oil pan gasket.... is not that choice somewhat dependant on the design of the timing chain cover? I have an original oil pan for my 66 but the timing chain cover needs a the thicker gasket. perhaps that part is not an original.Comment
-
Re: Small Block High Ol Pressure
Bill------
The timing chain cover does not affect the front seal. Regardless of what timing cover is installed, be it the 55-74 "tri-spoke", the 75+ "dish with a flat", or any other, the same front seal is used. It is the oil pan that affects the front seal requirement as I described above. If you require the thicker front seal, then I would say that your oil pan is a 76+ SERVICE replacement. These pans are virtually identical with the original pans except for the front seal radius. The original pans had a front seal radius of 2-1/4"; the later SERVICE pans have a front seal radius of 2-3/8".In Appreciation of John HinckleyComment
-
Re: Small Block High Ol Pressure
Duke,
So If you were going to replace an L79 engine oil pump with an OEM pump from NAPA would you replace the spring in the new OEM pump with the GM oil pump GM spring #3848911 as mentioned in your post?
You mentioned spring #3814903 as the '62 and up OE small block spring also. Is this the correct spring for the 250 and 300 HP engines?
Thanks,
James WestComment
-
Re: Small Block High Ol Pressure
What Joe said... The only small blocks that used the ...911 55-60 psi spring were late '63 to '65 mechanical lifter versions. Also, the P&A catalog lists the ...911 as applicable to '69-'72 SHP, which implies that it was used on the L-46, but I'm not sure if this is correct. It was used on the LT-1. Maybe some L-46 and LT-1 owners can chime in. All other OE small blocks use the standard pressure ...903 spring.
A very good indicator of which spring was OE is the oil pressure gage type - 60 psi for the ...903 and 80 psi for the ...911.
As far as the replacing the oil pump is concerned, I have stated many times that in 90-plus percent of rebuilds it is absolutely unecessary to replace the oil pump. The oil pump leads an easy life unless something in the engine disintegrates and the pump ingests debris that chews up the gears. It is very easy to disassemble, inspect, and "blueprint" by minimizing gear end play to minimize leakage (see "How to Hot Rod SB Chevys"), which yields the 40-45 psi at 2000 or below.
Replacing the oil pump, apriori, is a typical "engine builder" process because they are too lazy to do the simple disassembly and inspection, and since most replacement pumps do not have a proper relief spring you end up with hundreds, if not thousands, of owners who have excess oil pressure.
BTW, the commonly cited "10 psi per 1000 revs" is for seventies vintage RACING ENGINES, and there are plenty of mechanical lifter engines like the one in my SWC that never had any oil system related problems with the 40-45 psi spring despite some racing and hard use over its life.
The vast majority of engine failures due to "oil system problems" are caused by oil starvation due to low oil level or tire and suspension modifications that increase vehicle dynamic loading beyond the capability of the wet sump system to keep the pump pickup submerged in oil.
Back in the old days before dry sump systems were allowed, guys would run the system a quart over and this usually worked okay until tire technology allowed cornering loads to hit 1g and more. The higher the revs the harder it is for the oil to drain back into the pan, and this is exacerbated by dynamic loading, so you end up with two to four quarts up somewhere in the engine. Despite the dire manufacturer warnings of "DO NOT OVERFILL", I have never had any problems running my L-76 SWC or Cosworth Vega a quart over for track events, and I never attempted to remove this "excess oil" after the event.
DukeComment
Comment