When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
Chevrolet does not specify idle oil pressure (see the AMA specs). The spec for you engine is 40-45 psi at 2000 with the engine thoroughly warmed up. So report this number.
A 327/250 should idle butter smooth at 500 in neutral with an OE equivalent cam and idle oil pressure as low as about 5 psi is likely okay.
Bearing loads increase with the square of engine speed, so the loads at 500 are only 1/100 of the loads at 5000, and not a lot of oil flow is necessary at idle.
I recall reading back in the seventies that GM began lowing oil pressure on some engines as a fuel economy improving measure to reduce the parasitic load of the oil pump.
Sully, I think the consensus here among some very smart guys is that you shouldn't worry about it. As MikeM said, if you hear noise, investigate. And proving actual pressure with a mechanics guage is smart, but more than likely it won't reveal much.
I've owned a 250 HP 327 for 17 years with low oil pressure at idle that is consistent with the owners manual.
If you dwell on this or listen to too many more opinions you will have trouble enjoying your car. Don't do that. I can all but guarantee that your engine will run fine for as long as you own it.
Most everything that has been written in this thread is gospel regarding the small block engine and you should probably not worry further. However, if it were mine, the position of the needle would bother me every time I looked at it (which would probably be often in anticipation of something bad happening). Solely for peace of mind I would install an additional oil pressure gauge as an inexpensive investment in your driving pleasure, perhaps even one with a 0-60 range which would put the needle in a more favorable position.
Just get in the car and wind her up 'till the valves float in low gear and shove in the clutch. If it's still at idle speed after that, you should be good from now on.
Out for a sunny warm drive tonight. I am wondering if my oil pressure is too low. I checked the oil level and it's right where it should be on oil stick. At cruising speed of 50 mph, it shows a steady 40 lbs. When warmed up, idle at traffic light or stopped (Clutch in)it shows 10 maybe 12lbs? Normal? Thx, Sully
The center hub on the needle looks different than normal? Different than the one on the water temp gauge above it. The ring next to the black portion is thin and rounded, unlike the wider and flat one on the temp ga. Could that be a needle from a 68 and later? If so, could it be that this ga has been apart?
The center hub on the needle looks different than normal? Different than the one on the water temp gauge above it. The ring next to the black portion is thin and rounded, unlike the wider and flat one on the temp ga. Could that be a needle from a 68 and later? If so, could it be that this ga has been apart?
The temp gauge is from a 66 and up. The 63-65 cars came with 180 center lines, and changed to 210 in 66.
Man, you guy's have an keen eye and a deep wealth of knowledge of whats going on. I thank you all for your input. I agree that the 60# oil gauge was probably replaced by a PO. Why he put in a 80# one, who knows. I will try to look at all the suggestions given. The car runs very well and I will continue to drive the heck out of it this summer. I do feel a little more at ease with the low pressure. Thanks again as always. Sully
I know there is really no comparison but if it makes you feel better these turn in the 10,000 rpm range and they have no oil pump or filter. They oil by splash and after about 5,000 there isn't any liquid oil it has been whipped to a mist. They are my motors that I let a good friend use. Last year he went to a 3/8 mile oval and asked what rpm to turn it. I told him I didn't particularly like turning it 10,000 that long. The tachs on these record everything he turned it 8,900 on the straights and 8,600 in the corners for 2 1/2 miles. I kinda figured it wasn't going to live through that but it didn't hurt anything.
That is some major modification to the old Briggs and Stratton 5 HP engine! Look at that head and the block modifications for flow. Wow.
How much horsepower does it make?
20 years ago I had a customer that built these for Drag racing. His Nitro Burning 5 HP actually made 40 HP on the dyno. It sounded wicked. I never got to see his head design or block internals. 10,000 RPM's is way high. My old mini bike ( 45 years ago ) floated valves well below 5,000 but was fast for a mini bike back then with a 5 HP Briggs.
Years ago I managed a pretty good size engine shop. Then I had my own for a few years, one thing has always been true. People will not like low oil pressure but never complain about having too much. I have always stretched the spring 1/4" or installed a pink spring. Then there's never an issue with oil pressure. If it bothers you enough drop the pan and fix the spring. Do a google search about the filter you have collapsing. Then form your own opinion.
A couple of years back a friend of mine that has an engine shop called and wanted me to look at an LS6 BBC crank. This crank was out of 71 Vette. It had been ground once over the years to .010 .010. He had it ground again and was balancing it when he noticed no oil hole to the number 8 rod. He wanted me to drill the hole as he didn't have anything long enough or tough enough. Those are nitrided and the surface is really hard. When they were drilling the crank at the factory it got maybe 2" in and the bit broke. I had to drill it another approximate 3" to get it through. Point is it ran in a performance corvette 45 years with no oil hole to that rod. I would have never believed it had I not seen it.
Exactly where is this spring and where can you get this pink spring?
The spring is in plate on the oil pump on the small block. You remove the pin with a pin punch and stretch or replace the spring. Replacing is better because the spring is stiffer resulting I'm more over all pressure. Stretching will give more pressure but not as much. The spring comes in a Melling M55hv pump. It has 2 springs one for more pressure and one for more volume but not pressure. You can buy just the pink spring from Summitt. I rebuilt a Ford Escort for a young lady. I put the bypass in backwards. After a week or so it blew the oil filter off. I had to pay to have the engine pulled and replaced and go through the motor. Not a very profitable job.
The spring is in plate on the oil pump on the small block. You remove the pin with a pin punch and stretch or replace the spring. Replacing is better because the spring is stiffer resulting I'm more over all pressure. Stretching will give more pressure but not as much. The spring comes in a Melling M55hv pump. It has 2 springs one for more pressure and one for more volume but not pressure. You can buy just the pink spring from Summitt. I rebuilt a Ford Escort for a young lady. I put the bypass in backwards. After a week or so it blew the oil filter off. I had to pay to have the engine pulled and replaced and go through the motor. Not a very profitable job.
The spring operates against the spool valve in the pump and has nothing to do with volume. When pump pressure reaches the spring setting, it opens the spool valve and dumps excess pressure externally. It has nothing to do with volume. A special "high volume" pump using a bigger impeller and case is used for that purpose. High volume pumps are useful for race applications where very large journal clearances are used, and so a large volume of oil flow is needed to keep the bearings under hydrostatic lubrication.
Last edited by 65tripleblack; 04-27-2018 at 08:46 AM.
04-24-2018, 09:59 AM
