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I need to find someone that can overhaul the engine for my 1948 Chevrolet truck. It's running but is showing lower than normal oil pressure. I've replaced the oil pump, but that didn't solve the problem. My mechanic says the next step would be either overhaul or engine replacement. I can't find anyone in my area that is willing to overhaul the engine. The issue seems to be that the bearings have to be shimmed and the people I've talked to don't want to do that much work. I understand that any engine up to 1962 would work and be compatible with my transmission that was overhauled last summer. I live about 20 miles from Louisville, Ky. Any suggestions would be helpful.

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The main bearings have shims between the bearing cap and the block. The shims can be removed as necessary to adjust the main bearing clearance. As a rule the 1948 and up main bearings seldom require adjusting. They can be on the loose side and will not affect oil pressure. The main bearings are the only thing in the 1948 engine that get full oil pressure, The only way the main bearings will creat low oil pressure is if a bearing is burnt out, This if the babbitt material is melted out due to lack of oil With a burt out bearing the engine will have a deep sounding knock under load,


Gene Schneider
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Not hearing any noise under load. Engine is running strong, no smoking, no unusual noise.

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Might be good to hook up an external gauge to verify the accuracy of the dash gauge. Possibly a blockage in the line to the dash gauge .

Last edited by m006840; 08/27/22 08:47 PM.

Steve D
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If the pressure is bear 10 pounds at 50 MPH and would just keep driving it....especially if you do not drive on the interstates.


Gene Schneider
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Last month, my mechanic did a pressure check and said the gauge was reading correctly. How he did that check, I don't know.

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The pressure gauge shows about 10 pounds at highway speed. At idle it drops down to about 3 psi. It's disconcerting when I see drop down like that.

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It is normal to drop down by about 8 pounds at idle to 2 0r 3 pounds with hot oil ay idle
That is not a common high oil pressure engine.
Just drive and enjoy it,

Last edited by Chev Nut; 08/28/22 12:26 PM.

Gene Schneider
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My driving is mostly on the 2 lane county roads and state highways in my area. I do not drive it on the interstate. Speed is generally 45 to 50 mph. Trips are mostly 10-20 miles round trips. The truck doesn't get pushed hard. I have hauled up to 15 bales of hay in it, but think I'll leave that hauling to my 2004 Silverado.

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Oil pressure sounds good. My 48 is a little higher, but not much. Just drive it and be on the look out for another engine, in case you need it.


1946 Chevy 3100 1/2 Ton Pickup Purchased 11/18/17 Sold 9/20
1948 Chevy Fleetmaster Coupe, Purchased 6/20/2010
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Based on my experience with the 216 in my '37 those are very acceptable oil pressures.


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The 1937-1939 pump produced less oil prssure than the 1940 and up.


Gene Schneider
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What weight oil are you using? As long as the gauge registers any pressure oil is being circulated. On the 1948 weren't the main bearings replaceable shells?


J Franklin
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All Chevrolet engines had replaceable main bearing shells.
In 1948 and up the shells could be replaced individually if necessary, prior to that all sheels had to be replaced as a set and line bored......Although it was common to replace just the lower shell as that took all the pounding and the upper just went along for a ride.


Gene Schneider
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Have any of you heard of this? A post on Facebook suggested that I use 6 ounces Sea Foam in the oil to break up any blockages or crud. Put about 50-70 miles on the truck and then drain the oil and replace it with Del vac 15w-40 oil that is normally used in diesel engines. I added the Sea Foam about 10 days ago and have driven the truck almost everyday since. I'm torn about putting the Del vac oil in my truck.

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Do a search of Sea Foam on the internet and you will find out it contains no special content.
Regular 10W-30 passenger car oil actually has more additives desinged for passenger cars than Disel oils.
The 40 weight when hot MAY increse your oil presure but only because the #40 is "thicker".

Last edited by Chev Nut; 09/19/22 07:37 PM.

Gene Schneider
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In my opinion,
Regardless of how fantastic the additive package in Del Vac is (and it is), 15W-40 is FAR to thick for a 1948 Chevrolet engine.
Viscosity is just as important as any other oil attribute.
No matter how good the additives are, the oil has to get where it's needed in sufficient quantity first and foremost. Especially at start-up.
Using a thicker oil in a low pressure Chev six may raise the oil pressure, but it will actually reduce the amount of lubrication the pistons, cylinder walls, camshaft, lifters and anything else relying on oil thrown by the dippers get.


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15W40 in a 216?

No. Just no.

This oil system is nothing like a modern engine. Pressure is not what matters, flow is. I hate to be "that guy", but read the shop manual. The rods are oiled by squirters. They might not squirt far enough if the oil is too thick. The rods might not oil. Even if they do get oil, it might not flow into the bearing well because they are not pressure fed! There is nothing to force the oil into the bearing other than momentum, force of habit, etc. Engines like this also depend on splash for lubrication of some parts. Splash oiling does not work well when the oil it too thick

Nothing heavier than SAE 20 or 20W back in the day (OK maybe SAE 30 in Death Valley). 10W30 is probably a good choice today.

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I caN'T FIND MY NOTES BUT sEA FOAM WAS LIKE 90 PERCENT PALE OIL AND 10 PERCENT ALCOHOL.

If it would "loosen things up"" it could end up plugging up oil passages.


Gene Schneider

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