Well... Metallurgically speaking..babbitt is a general term for an alloy of copper, tin, and antimony known as a babbitt bronze. But there are thousands of different types of babbitt alloys based on the ratios of these elements and other elements (Pb)that give babbitt different hardness/wear etc. properties.
Babbitt can be poured into a hole and used for a bearing, OR babbitt can be made into an insert, metal coated, and slip fitted into a hole. Its all babbitt.
Babbitt, as used on a type of main bearing insert can even be coated with an outer layer of a harder/softer metal alloy and thus when you see wear it looks like "copper' showing thru the outer layer in streaks. It is known as a "babbitt insert" cause that's the general metal alloy the center of the insert is made from. Babbitt can even be an outside coating on a bearing!
In the 1950's days the mechanic would not need to pour the babbitt into the rods himself; he would send out a core exchange of the old rods for a new set of rods poured in a factory.
He would just replace the babbitt main bearing inserts with new ones as he does today!
As far a Detergent versus Non-detergent, well "Search" this site and the debate rages! But in general, if you look at the "oil clearance specifications" on the rod bearings from Chevrolet you will see the following:
1941-42 .001-.0025
1946-51 .0003-.0013
1952-53 .0003-.0013
All the above babbitt rods and low pressure high flow OIL system.
Then with full oil pressure and rod "inserts".
1954-55 .0007-.0025
The point being the clearance opens up with factory inserts high psi oil pressure. The factory inserts are a different hardness than the poured babbitt and any dirt potentially impregnating itself "in-the-bearing" should theoretically get trapped in a full pressure oil filter first. If not, the insert must be changed as it wears beyond spec. Slap in a new one.
Babbitt rod clearance is pretty tight and dirty oil on a soft bearing is a case for impregnation. Thats exactly GOOD for the Crank journal, to have a 'little' dirt imbedded/incased into the rod bearing INSTEAD of the crank journal. If dirt gets stuck somewhere, better imbedded into the bearing and thus the bearing 'sacrifices' itself. Un-shim the rod caps to take up for wear.
BUT unfiltered/half filtered detergent oil passes a LOT of dirt passed a babbitt rod bearing.
Detergent oil has additives and scrubbers that "clean-up" ALL the engine sludge/dirt and deposit them in an OIL FILTER under relativeley HIGH pressure.
Non-detergent 'lightly suspends' the dirt into the oil, and drops it into the pan, but does'nt scrub it free from surfaces. You clean the suspended dirt out when you change the oil with fresh oil, VERY OFTEN, or the dirt gets to be too much for the oil to carry. (old mechanics then cleaned the other waxy engine gunk from the engine with a flush of Kerosene or diesel)
Old pre-1954 216-235 Chevy engines were NOT designed to filter oil and thus where does the dirt from detergent oil go? Round and round your bearings till ya change it.
Non-detergent tends to leave (drop out)the waxy-dirt stuck to the valve covers, oil pan , etc. INSTEAD of breaking so much free and passing it thru the bearing surfaces.
In short CHANGE any type oil a LOT!. It is a 50/50 trade-off to break the dirt free or leave it in place, and will always be a controversial trade-off in old engines. WE are in between the Devil-and-the-deep-blue-sea when it comes to oil types.
Finally, some folks are a tiny bit concerned about the additives in "modern" oils and their effects on the old babbitt alloys. Little professional research is done in the labs, but it is known that some chemicals can attack and cause babbitt to "bloom" (ie expand) and then crack and spaul. This happens when antifreeze gets into your oil!
I can find NO evidence that new oil additives attack the babbitt, BUT I follow the ancient wisdom of master-mechanics and advise new babbitt alloy rods to use non-detergent oil and change very often. BECAUSE babbitt rod rebuilding is becoming a lost art; and babbitt rods were designed for non-detergent; and the effects of non-detergent oil are well known with regards to babbitt, ...and the old men mechanics told me so.
New oils may be better, they may be perfect for babbitt, I just cant find and professional research sources that say yes or no. So in a fresh/clean rebuild use either detergent or non and
change the heck out of either and thus hedge your bets!
Clean oil passing around the bearings is what is important !
Finally, as far as Kerosene in winter oil, there was no Winter weight oil (10w-30) way back then, and if you didn't thin your oil then you lost your engine. Worst enemy to an old Stovebolt was not getting oil to the bearings&rockers on start-up.
Warm your Stovebolt up to operating temp in winter or suffer much wear and even gasoline into the oil cause of the hand choke.
FOR MORE INFORMATION SEE THIS GREAT SITE:
VCCA CHEVY SITE
