VCCA Home Forums TECHNICAL - 1945 AND NEWER 1949-1954 1951 235 truck engine -- oil pressure and more

This is somewhat related to the recent question about a 235--and maybe this question should've been posted to the trucks section..., but here it is:

What should oil pressure should this engine maintain?

My brother just bought an 1951 unrestored 1.5 or 2 ton with 2-speed rear (I don't know which--haven't seen it yet). It would be a 235 from what I understand. If the engine is original, not replaced, would it have babbit bearings for the rods? Would the mains be the old thin shell type, or inserts? Would it have solid lifters?

Are there obvious characteristics to visually id the engine--if early 235/later 235 or something else?

He drove it home (about 90 miles)without any snags--it is supposed to be low mileage. He says everying works and it runs well. But the concern is oil pressure: He said runs about 8 lbs when warm. I realize with my 36 this is not a problem--just about right with splash/low pressure lubrication. But should the 235 be carrying more? Apparently no untowards engine noises, though.

Also, any good resources for information you all would recommend for this truck? Shop manual would be a good idea?

Thanks!

A 6000 series truck would have a 235 engine.A 4000 series a 216 engine.The push rod cover on a 216 goes all the way up to the valve cover.On a 235 its about 6" tall and goes up to the top of the block (not head) only.Either engine uses the same oiling system and bearings.Would be the splash and low pressure to the mains.The connecting rods have dippers and the rod bearing s are thin babbit spun into the connecting rods.They are adjusted by removing shims.The main bearings have thin wall babbit inserts and are also adjusted by removing shims.All 1929 and up 6 cyl. engines had inserts, just had thicker babbit material.The thickness was reduced several time between 1929 and 1947.Those models required line boring of the main bearings if the bearings required replacing.Later Chevrolet made precision replacement bearings for them also which did not require line boring.
The normal oil pressure on a 1940-53 engine is 14 pounds with hot oil at about 2500 RPM.This would be about 50 MPH with a stick shift car.At idle they will drop down to about 7 pounds.
Low oil pressure could be caused by very loose main bearings...you would here them pound under load.Could be caused by a stuck by=pass valve in the oil pump or the oil pressure regulator valve on the side of the block...tin cover,3 screws, left side, center.
Could also be caused by oil being contamined with gas.If it were mine I would change the oil and filter if so equipped,refill with 10W-30 and see what happens...and possible add a Qt. of Rislone in place of a qt of oil.
The oil pressure on a pre-1940 engine will be 13 pounds at 50 mph and will drop to 3 or 4 at idle....some where in between that at 35 MPH.

Thanks for the information about the 235! I'll pass this along to my brother.

The engine in the 36 (207) runs at about 7-10 lbs pressure after hot (at 45-50 mph)--but the bearings do need going through --taken out shims in the past. At least one rod knocks a little becuase out of round crank. I've got a NOS crankshaft and rods to put in someday in the future for the 36!

Are there replacement precision main bearings available for the 36 207 engine? The original were line bored, but I thought later on GM made precision types available for the earlier engines. It don't have the Master Parks book at the moment, but I thought they were listed. If so, does any have some for sale? That way it would be all brand spanking new on the bottom end!

I'm not referring converting to inserts in the rods, etc, but period precision main bearings. Thanks again!

In 1948 the original type inserts were discontinued and the precision were sold for replacements.All 3 (or 4) must be installed as a set.After that was done if one only would require replacement it could be done.Name brand after market bearings also changed to precision atfter that time.Also the bearings became available in available in undersize also....002",.010",.020 and .030" ...prior to that they were all semi. and were sized by line boring.
The front,center and rear main for a 1936 would be 3847394,3847395 and 3847396 for Std Size in precision.I have run thsoe with a new crankshaft in my 1934 for the last 35 years.At that time I installed the later gear type oil pump conversion offered by Chevrolet.At 50 MPH with hot oil the pressure is 17 pounds (10-30 oil)-and no, it dosen't leak.

I have been running WalMart oil, Tech 2000, for several years. It seems to be very highly temperature compensated. It may be my imagination, but I think it has higher hot viscosity that the Exxon and Castrol I used previously. I have certainly used enough of it to confirm that its performance is very good. My 1990 Voyager van runs like new with normal pressure at 210K miles! Also an '82 F*** six PU a kid and I rebuilt 12 years and 60K miles ago does the same. Maybe this high viscosity would keep the mains a little fuller??