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Oil pressure '65 327/250HP? Too low at Idle?

 
Old 04-23-2018, 08:00 PM
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Sullyvette
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Default Oil pressure '65 327/250HP? Too low at Idle?

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

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Old 04-23-2018, 08:03 PM
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seems normal to me
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Old 04-23-2018, 08:05 PM
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reasonable at idle, good on the road.... what wt oil are you using?

Bill
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Old 04-23-2018, 08:08 PM
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Shell Rotella T4 15W40. Thanks for your input guy's. Sully
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Old 04-23-2018, 08:29 PM
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That looks a little low. Especially when using 15W40 oil.
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Old 04-23-2018, 08:39 PM
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Robert61
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Its definitely lower than I would like but that doesn't mean anything. Has anything been done to the engine or did it just suddenly show low. What kind of oil filter do you have on it. I have seen 2 of the biggest national brands wad up like a shop wrag and stop the oil flow. But if you checked the specs they would more than likely say its in spec
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Old 04-23-2018, 08:52 PM
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If it's idling down around 500rpm. then I wouldn't worry about it, but if it's idling around 7 or 800 I would investigate the gauge and the copper line first.
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Old 04-23-2018, 08:55 PM
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65GGvert
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I'm not telling you there is a problem, BUT, I've owned several and have never had one that low at idle. I'm sure the minimum spec is down around there close depending on idle speed, temp, etc.

Edit:
I just noticed you have an 80lb gauge, so not quite as low as I first thought. I have no experience with that gauge, it just seem low to look at the needle down there. These guys can tell you what is normal.

Last edited by 65GGvert; 04-23-2018 at 09:08 PM.
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Old 04-23-2018, 08:56 PM
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Originally Posted by Robert61 View Post
Its definitely lower than I would like but that doesn't mean anything.
Correctimundo.

Yee old small block always seemed to tilt towards low oil pressure at idle and then again most of those I've run across were engines rebuilt I don't know how or when so who really knows unless they have done their own overhaul.

I know that the 250 HP 327 in my Impala flickers her oil pressure warning lamp in gear at a stop on a hot day, especially with the factory A/C on. The owners manual says to ignore any such flickering oil pressure warning lamp unless it remains illuminated once underway in which case you should pull safety off the road and turn off the engine which of course is good to know.

My 396 & one of my 440's nearly pegs the gauge cold and underway is all of 65-75 pounds, too much but builders are putting in these high volume pumps to placate guys like you (and me).

Oil pressure going down the road is all you need anyway. Raise your curb idle a tad if you want to move the needle a little. That and some 20-W-50, and a nice glass of red. Everything will look better.

Dan
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Old 04-23-2018, 09:33 PM
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Before I did anything I would check the pressure with a high-accuracy pressure gage with actual measurement graduations.

For a 15W-40 oil, 10-12 would get my attention, too.

Is this a recent development, has it been lowering for awhile?

If the gage is accurate, and it has been lowering over time, I'm wondering about the wear of your crankshaft bearings.

Is it as low when the oil is cold?

Might be worth it to get an oil analysis done. To look for excessive bearing wear.
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Old 04-23-2018, 11:25 PM
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Fram PH-30. Just changed the oil within the last two weeks. This is the same pressure since I bought the car 1 1/2 years ago. No Air, no flickering or wild fluctuation. Idle is set at about 800. Since I changed the oil filter, I've noticed a drip on the bottom of the filter, never had a leak/drip there before. Might I have been given the wrong filter? Rebuilt in late 80's. Not stock. Thanks, Sully




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Old 04-23-2018, 11:26 PM
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Sorry for the tilted view!
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Old 04-24-2018, 02:19 AM
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As already mentioned, hook up another mechanical gauge and double check your oil pressure before doing anything.
GM would not warranty an engine for low oil pressure at idle unless it was below 10 PSI if I remember correctly. The low pressure lights did not come on till 6 or 7 PSI again memory but I am close. John Z will know exacts.
40 PSI at speed is just fine.
I like to build my engines tight and with tight bearing clearances the oil pressure at idle will be right at the oil pumps set pressure relief.
Many shops built engines loose and a loose engine can spill a ton of oil at idle leaving you with low pressure at idle. Some think a loose engine can rev faster and make more power. I don't buy into this thought.
You might switch to a straight 40 W if the low oil pressure bothers you. Many performance engines ran that back in the day it works well in loose engines.
The OEM spec for bearing clearance said anything from .001 to .0045 was OK.
Basically this covered them as in spec with nearly all engine clearances in the old days.
Personally I like to be .00175 to .002 rods and mains. Many new engines run this or tighter and new engines last a long time.
Built one engine and the crank was a little on the low side leaving me with .00275 Rod Clearance. Engine held only 25-30 at idle and 60 running. I knew it when I built it but did not spend the money to make it tighter so I had to live with it. It ran perfect but bugged me. It was a diesel so I did not have the options in sizes you have with a small block to fix clearances with bearing sizes.
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Old 04-24-2018, 06:45 AM
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Frankie the Fink
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Correct.

Dash idiot lights came on at 5-7 lbs. This car will prob go 200,000 miles just like it is but, yeah. my eye would constantly be drawn to that gauge. As noted, I've run an extra gauge more than once to verify a symptom....
(Water temp/oil pressure). Might be worth it just for some piece of mind. Also check the routing of the steel line to the gauge (its NOT copper) and make sure there are no kinks/sharp bends/etc..
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Old 04-24-2018, 06:59 AM
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My BB is the same way, bothered me at first but it runs great so I don’t let it bother me anymore. GM says 10 psi for every 1000 rpm’s is normal anyway.
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Old 04-24-2018, 07:54 AM
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I have an L76 and that's exactly where mine reads at idle 800rpm.80lb gauge, 10W40. at cruise 40lbs. it used to bother me looking at it idle. does not phase me anymore.
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Old 04-24-2018, 08:22 AM
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Duck916
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I wouldn't worry about it. As long as you've got some oil pressure at idle and a decent pressure at cruise, you're good to go.
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Old 04-24-2018, 08:29 AM
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If your hydraulic lifters start clicking at idle, it's time to shut it off and investigate.
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Old 04-24-2018, 09:26 AM
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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.

Last edited by Robert61; 04-24-2018 at 09:53 AM.
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Old 04-24-2018, 09:47 AM
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I don't think the low idle pressure is a big deal either. I remember some time ago there was a discussion about the factory installing just one half of a .001 oversize bearing shell to close main or rod clearance if it was excessive.
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