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322 Nailhead Oil Pressure when idling


Ralph55

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I got my 1955 Super's engine rebuilt in January. Before my idle oil pressure was about 50% after 10 miles - and it never went below that.

 

After the rebuild it goes down now to the end of the white arc (like in the picture attached) and it stays on 50% only for the first 5 miles when the oil is still cold.

 

I can't tell whether 

 

a) the rebuild restored the perfect factory-like settings and the lefthand-side of the white arc is OK      OR

b) something went wrong with the oil pump re-assembly and I lost significant oil pressure

 

Can the needle go any lower than that - or does this position mean the engine has still about 10 PSI pressure?

 

Maybe some of you Buick veterans can enlighten a newbie like me 🙂

 

Best regards 

 

      Ralph 

 

buick_idle.jpg

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Need more info like oil viscosity, idle speed, and how many miles since rebuild.  Don't worry yet as long as there is some pressure and the engine is quiet.  You may need to attach a know good external gauge to see what the actual pressure is.

 

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Conventional wisdom might indicate the oil pressure at idle should be higher after a rebuild, getting the bearing clearances and such in "tighter" territory than "worn" territory.  Which leaves the spring in the oil pump as the other possibility.  Is the pump new, refurbished, or untouched?  Is the pressure indicated in or out of gear?

 

Need to verify the engine hot/base idle speed and mixture adjustments, just to see where they are.

 

Just some thoughts,

NTX5467

Edited by NTX5467 (see edit history)
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Ralph  Rid your engine of the 20W/50 RAT NOW !!!!!!!!!. Bad choice for breaking in a new engine. Way too heavy.The state of the art break in oil is a synthetic  (yup !!!! - a SYNTHETIC - imagine that - break in oil !!!!!!!!), break in oil made by Amsoil. Look it up and you will understand why. You'll run it for just a few hundred miles, and then we can talk about whether you will operate your engine on the very best full synthetic oil available, or just a very, very good full synthetic oil. By the way, what brand/type of 20W/50 did you use, and why ?   -   Carl 

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49 minutes ago, C Carl said:

Ralph  Rid your engine of the 20W/50 RAT NOW !!!!!!!!!. Bad choice for breaking in a new engine. Way too heavy.The state of the art break in oil is a synthetic  (yup !!!! - a SYNTHETIC - imagine that - break in oil !!!!!!!!), break in oil made by Amsoil. Look it up and you will understand why. You'll run it for just a few hundred miles, and then we can talk about whether you will operate your engine on the very best full synthetic oil available, or just a very, very good full synthetic oil. By the way, what brand/type of 20W/50 did you use, and why ?   -   Carl 

That is an invalid opinion.  Leave the 20w50.

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Well, you have VASTLY more experience than I do. However, as this is, among many things, also a debating forum, could you please explain and elaborate your position. Particularly vs. Amsoils info on their new, supposedly well engineered product. As many do, I learn something new every day I tune in here. No one ever learns anything as well as when they stand corrected. At my age and stage of life, I need all the help I can get !          Thank you,    -   Carl 

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Just to explain: The engine received the break in not inside the car but on a test stand. For breaking in the new engine they used a special oil which was replaced by the 20W50 afterwards - but I don't know the type.

 

The explanation for choosing the 20W50 was that the 50ies engines have gaskets which always leak a little bit - using heavy oil reduces the amount of oil working its way through the gaskets...

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The idle speed may be very low like my '56's 450 rpm.  At warm idle mine drops to about where yours is after 10-15 miles. But as soon as it is above idle the gauge returns to the H (high) area.  I do not know the actual reading but from observing other GM gauges in this era I noticed many with numbers show a high reading to be 30 lbs. I figure mine to be the same. 

If yours is similar then your gauge pictured would represent 10 lbs,  but all of this is based on a lot of "if's". Was the oil pressure like this from the first mile of use? And did you see what the oil pressure should be in your manual?  It does seem low to me based on 160 miles of use. My 56 is around 100 k right now.

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ah... that's what I needed to know: initially my oil pressure is between 50% and (H)igh - after driving a while it drops when idling, but returns to high as soon as I hit the gas pedal...

 

I've got the original driver's manual - but sadly it doesn't contain anything like "how to read your Buick's gauges". I'm sure there was some kind of engineering intention with the while arc when they designed this car - but the knowledge what it really means seems to be lost now (it isn't mentioned in the shop manual either)...

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As Old Tank stated...... you need to attach a good mechanics oil pressure gauge to your new rebuild.

Old instruments, old sending units/tubes, etc can fluctuate greatly; esp.after the handling during the rebuild.

 

Do this, and you can properly correlate the actual pressure with the 64 year old instrument.

 

 

 

 

 

 

 

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C Carl , your first post would lead one to believe that 20w50 is poison and only synthetic should be used.  Synthetic is ok in newer vehicles as is low viscosity that they were designed for.

 

I use 20w50 Castrol in my 4 early nailheads with no issues.  On one the cylinder heads were changed at 80,000 miles (not oil related problem) and the cylinders still had hone marks and the cam and lifters were pristine.  It now has 100K and is running well.  A 92 Mercury was retired (bad transmission) at 435,000 miles after a steady diet of same 20w50.  Now if I had been using some synthetic we would be saying that is some great stuff; the point is synthetic is not necessary in these old engines.

 

Back to Ralph55.  If the idle setting on the carb was not changed, the new engines will be idling slower until broken-in (3000 miles);  increased friction may have even the 20w50 oil running hotter reducing viscosity.  On my rebuilds, I set the initial idle speed at 650 rpm and as it is broken-in the speed will increase and I set it back to 650 rpm as needed, with the final speed at 600 rpm (650 rpm on the ones with air conditioning).

 

Other sources of lower pressure:  rebuilt/refurbished rocker assemblies will sometimes put out a huge shower of oil unlike the originals just oozing some oil...this will reduce the pressure; new cam bearings when installed need to honed to fit the cam journals.  Most machine shops do not have the tools to align hone the different sizes and will take the old cam, cut grooves in the journals and crudely ream the bearing.  Until the babbitt re-flows and heals, you will have reduced oil pressure.

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tank & the other Buick fellows, your comments are appreciated: I'll be meeting the guys at the engine shop tormorrow in the morning and now I've got some questions I can ask and some things we can try 🙂

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On 7/7/2019 at 7:24 AM, Ralph55 said:

ah... that's what I needed to know: initially my oil pressure is between 50% and (H)igh - after driving a while it drops when idling, but returns to high as soon as I hit the gas pedal...

 

I've got the original driver's manual - but sadly it doesn't contain anything like "how to read your Buick's gauges". I'm sure there was some kind of engineering intention with the while arc when they designed this car - but the knowledge what it really means seems to be lost now (it isn't mentioned in the shop manual either)...

 

This is normal from my experience.  For mine, when cold the oil pressure when sitting at a stoplight will stay high.  Once good and warm the oil pressure will drop to the lower side of the gauge just like yours.  Give it gas to go and oil pressure increases well into the normal range.   This is after putting in new rings but used the crank bearings that were there because it was not broke and did not need fix'in. 

 

 If the 322 is not clattering and carrying on like it is eating itself alive you are good.    

Edited by avgwarhawk (see edit history)
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