What weight & type of break in oil might be recommended for an old straight 6 cylinder engine from late 30’s. (Detergent vs non detergent; 5w20, 10w30 or?) A few specifics: It’s a splasher engine with no oil filter of any kind. The replacement piston rings are the original iron rings (NOS) & are “pinned rings” if that matters. As of now I have “not” decided to do anything with the cam, ie re-grinding of the cam & lifters to a more performance grind but I’m thinking about it. Since currently it’s only a partial rebuild (hone cylinders & new rings, plus new valves & guides), I’m not doing bearings as they are babbitt type & that would be cost prohibitive. One caveat to the bearings is the rod ends have shims which can be removed to return them back into spec at the crankshaft journals and that will eventually be done. The engine & oil pan has been de-sludged. I haven’t & don’t plan on pulling the engine out to plastic gauge the mains or cam bearings, thus those will be unknowns. While the engine has only 37k original miles, who knows how the engine was cared for over those miles. Here are the engines specs when she was new: Crankshaft - end play of 0.006-0.012” & - bearing clearance of 0.001”. Camshaft - radial clearance 0.0015” & Connecting rods - lower end clearance 0.001 & - upper end radial clearance 0.0003”. Any recommendations would be greatly appreciated! Sent from my iPhone using H.A.M.B.
You're not really breaking it in, it's already broke in. Unless you do something with the cam and lifters I don't see a reason you can't just put oil in it and use it. The rings will seat soon enough being cast iron.
No break in oil needed. That engine was probably engineered for straight 30 grade motor oil for most common temperature ranges, maybe SAE 40 for extremely hot environments, or maybe SAE 20 for colder climates. You're in Montana, I'd say SAE 30 is probably right for you, though may be a little heavy in the winter. You're engine does not need a heavily additized motor oil, but it wouldn't hurt. I don't see why a good 10W-30 motor wouldn't work well for you. Since you've cleaned it up, a detergent oil shouldn't cause any problems with old sludge build up. Have you considered adding by-pass filtration? Now's a good time to do it.
Back in the 50's I overhauled a few Hudson splasher engines. I always used SAE 30 oil and it worked fine. Remember to fill the upper pan (splasher tray) with oil when putting the pan on. Hudsons have very low oil pressure in these engines as all the oil pump does is fill the upper pan. By pass filters don't do much good because of the low oil pressure.
Yea, right! LOL. Take that to the bank. Please, after a few thousand miles let us know how it is doing. I am betting it will be great. Ben
Haha laughs the guy with a stable and appropriate viscosity across just about every conceivable temperature using 5w-30. Maybe @Blues4U could post charts based on data that compares the viscosity of say SAE 30 and 10W-30 (or 5W-30) over 0 to 100 C. It would help illustrate why these grades have been recommended.
I'd do a straight 30w non-detergent. The theory being that the detergent is meant to keep the crap suspended in the oil so the filter can remove it. With no filter you want a non-detergent so the stuff will settle out of the oil to the bottom of the oil pan. I got this information from an oil company rep years ago. Or you could do the motor a favor and add a filter.
Blues4U n bigdog got it correct. The older mills were "heavy oil" engines. Don't like it, but they do. Just run some 30wt for a bit, then drain, repeat. Take it easy for awhile, you'll still find junk in the pan for awhile. Once oil stays clean, you can try 10w30 if you want, although I'd stay w/30w if you don't run it when it's cold out. I wouldn't stress mill 'till you know the bearing clearance(s) are still ok. Nothing wrong w/babbitt bearings if they're right. Since I'm curious, what brand n size of mill? Marcus...
Since you have had the pan off for cleanup make sure all the troughs are clean. I would use a good assembly lube on the rods and cam lobes and spin the oil pump with an old long screwdriver shaft to make sure the troughs have oil. Your oil pressure gauge should read 15 psi or more cold for 30seconds to a minute to fill them. Make sure the scoops are facing the right way. Good luck.
I'm not a Hudson expert, but as far as bypass filtration goes, lower pressure would actually be a good thing. The filter would have greater efficiency at lower pressure.
Well, that is partly correct. However, detergents do more than just hold particulates in suspension, they also serve as anti-oxidants, they neutralize free radicals in the oil, breaking the chain of oxidations, and they neutralize acids and corrosives to protect soft metals. They also will hold the dirt in suspension as you drain hot oil out of the pan, helping to prevent the buildup of crap in the pan and the top of the head. And, detergent oils also have other additive chemistry to improve the performance of the oil and protect the engine. If he adds some bypass filtration he'll get even more benefits.
Hudson splasher engines have a oil pressure of 3 or 4 psi. The oil pump is a piston pump driven of the center of the cam. the output dumps on both ends of the upper pan which has 6 or 8 troughs for the rod dippers to get oil from. every thin. is splash lubricated including the mains. I don't remember ever seeing one with a oil filter. The rod dippers are part of the rod cap forging. The engine had Siamese cylinders which required offset rods. The use of pinned piston rings was said to keep the cylinders round. The main bearings were bronze backed Babbitt and held in the block and main with brass screws. They were very different than most other makes of cars.
Thank you all! Great information from everyone. I’d read somewhere in the past about the no detergent oil & how it would not suspend stuff in the oil & from the bottom of the oil pan I can attest to a lot of crap dropping out of the oil! My question was if the lighter weight detergent oil at cold temp say a 10W30 would be of benefit before it turns warm & is a 30 weight, over the non detergent oil at 30 weight at cold start up, not suspending stuff to possibly damage the engine. Thank you for the recommendation on assembly lube, I picked up Permatex I believe it was & am making sure to coat the cam lobes, lifters & journals too. I’m not sure of what else to coat? Geezer, you definitely know your old Hudson engines! As I’ve been told too the oil pump just pushes oil to the top tray at 4-5 lbs. I haven’t seen any old filters used but I did see a guy build a filter kit using two modern filters. Which I’d love to use, my only concern would be if adding a filter between the oil pump & the upper tray would somehow starve or slow the volume of oil it is currently receiving. I actually was (cleaning) digging around in the engine troughs a while back & did find some chunky things which didn’t belong there so another good recommendation. I also have tried to make sure the main bearing holes which are fed by troughs are not blocked. I was able to visibly see the end bearings feeder holes but haven’t yet seen the middle one, I may need to buy a mini snake camera to actually see them. Sent from my iPhone using H.A.M.B.
Wow, splash to the mains, or gravity if you will..Either way I find that scary...I suppose they did ok if kept in the rpm/load range designed for but still scary..So now I think the roller mained, light Babbitt rod Tecumseh engine [18hp] that I was getting 45hp at 6500 was still splash lubed; I never thought about being scared!
did you ever open the oil fill plug on a splash lube lawnmower engine, when it's running? do it some time....you'll never worry about the bearings getting oil, ever again
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