What oil to use for my rebuilt engine?

[KNicholas2]

We just finished totally rebuilding the engine on my '42 Plymouth. What is the best oil to use (type, weight, brand) for the initial start up and brake in?

Kim Nicholas

[Young Ed]

The shop we use has always said straight 30 non detergent for the break in. Then change to whatever you plan to use after the first couple 100 miles.

[48mirage]

We just finished totally rebuilding the engine on my '42 Plymouth. What is the best oil to use (type, weight, brand) for the initial start up and brake in?

Kim Nicholas

Try this link.

http://www.cranecams.com/pdf/548e.pdf

[Frank Elder]

Did'nt someone post that our engines reqire a zinc enriched oil for break in?

Like shell rotella?

[Normspeed]

Hi, I broke in my fresh motor with Castrol GTX 5w30. Then I went with Shell Rotella T 15w40. Now after 11,000 miles, the next oil change I'll be using Rotella Synthetic 5w 40, for winter use.

[Don Coatney]

The shop we use has always said straight 30 non detergent for the break in. Then change to whatever you plan to use after the first couple 100 miles.

What is the reason for non detergent oil for the break-in? I would think detergent oil would be better as it would help clean any residue left in the engine after the re-build.

[Frank M.]

Don: I was told years ago that the use of 30wt.non-det. oil was to build a varnish type coating on the inside of the cyl. walls that matches the new piston ring striations,forming a good seal. It seems to have worked in my experiences. That is the glaze that you have to break thru when you re-ring. It always made sense to me. If someone has a better explanation,Id really like to hear it. So far tho. thats the best I can come up with. Frank M.

[Young Ed]

What is the reason for non detergent oil for the break-in? I would think detergent oil would be better as it would help clean any residue left in the engine after the re-build.

You know I never really asked. He's been building these probably longer then I've been alive so I took his word on it.

[De Soto Frank]

One thing seems to be a "universal truth": do NOT use synthetic oil for break-in - its friction-reducing qualities actually inhibit the critical "wearing-in"/ seating of certain parts. Once the break-in proceedure is complete, then synthetics can be considered, if you really are so inclined

More critical than Detergent versus Non-Detergent oils, I believe that SAE-30 is too thick an oil to use in a fresh engine.

The clearance between moving parts is tightest in a fresh engine, and the potential of parts "running dry" is at its greatest if the oil is too thick too circulate.

This post is the first place I have read about Non-detergent oils allowing a "varnish coat" to build-up on the cylinder walls, thus sealing the rings...

I have read in several books and magazine articles that proper seating of piston rings is a function of how the cylinder bores have been finish-honed (the "cross-hatch" pattern varies, depending on whether the rebuild uses cast-iron, moly, or chrome rings), and the proceedure used for the first hour of break-in running (after much more running than this, the cylinder walls have lost much of their "tooth" from the honing operation, and little further ring "seating" occurs).

Proper ring seating is achieved by slowly accelerating the engine ( preferably in the car, and out on the road) under load, then releasing the throttle and letting the vehicle coast against engine compression, down to idle, then repeating the process. This proceedure (particularly coasting against the engine) increases the ring to cylinder wall sealing pressure, and helps the rings to seat more quickly and evenly. ( Of course, one has to make sure the vehicle is not spewing oil or coolant, and that there are no unusual noises or other issues, before taking to the street. )

Supposedly, just running the engine at a fast idle in the driveway, while easy on the bearings and valves, does not contribute to thorough ring break-in.

The Crane Cams break-in proceedure link posted above is worth reading, particulary for the info about pre-lube at assembly, priming the oiling system before cranking the engine over (or starting-up), and the importance of keeping the engine running at 2,500 RPM or so for the first half-hour, to insure adequate oil flow to all areas of the engine.

Which brings me back to my concern about "adequate oil flow" - back in the days when our flatheads were new, many auto makers used /recommended a "break-in oil" - which was usually a light-weight oil, SAE-10 or SAE-20 for the first 500 miles. Oil does no good if it is too viscous to get between moving parts.

The last rebuild I did was about three years ago on a Chrysler RB-383 V-8, in a 1960 Chrysler Windsor. I prelubed the cam & lifters with the mfr's lube-paste (was either Crane or Edelbrock cam & lifter set), then prelubed bearings & crank with Valvoline SAE-30 HD (detergent) motor oil from a squirt can, and dipped the pistons head-first into a clean conainer of more Valvoline SAE-30 HD oil, up past the oil-rings, then installed into the cylinder bore, which had also been swabbed-down with the same oil.

(My guidance was "Rebuilding the Big Block MoPar", from HP Books)

So far, this was all pre-lube done at re-assembly time.

When the engine was dropped into the car, I filled the crankcase with Valvoline 10W-30 detergent oil. That is what stayed in the engine for the first 500 miles (or so). I primed the oiling system before installing the distributor using a drill (the flathead's cam / oil-pump design prevents this trick), and once the engine fired. I set-it up on fast idle, per the cam break-in instructions.

I did not get it out on the road as soon as I would have liked for the ring break-in proceedure, but the rings (Hastings Moly) seemed to have seated fine, and I have since put nearly 30,000 miles on this engine with no sign of oil conspumtion.

All that said, if someone's preferred mechanic has been rebuilding engines a certain way for decades, and they all turn-out well, then it would seem that their methods must have some merit.

I guess using Non-detergent oil for breaking-in is no worse than our cars saw when new, but if I were to use a "straight-weight oil" for break-in, I would probably use SAE-10; I would not go heavier than SAE-20.

Once the break-in has been achieved, I would see no benefit to continuing to run Non-detergent oil; you've got a fresh, clean engine now - keep it that way by running the best detergent, multi-weight oils you can get.

That's my take on the subject; I'm sorry I am not able to quote my sources that I paraphrased above... I have to dig around for books and mag articles.

I'm intrigued by the concept of Non-Detergent oil aiding ring break-in...

Over the years I've heard all sorts of stories about engines that were difficult to break-in and "rings that wouldn't seat" (cast-iron rings), and folks even pouring slurries of Bon-Ami mixed with oil down the intake to "help seat the rings"...

If I can find my rebuild / break-in info, I will post that biblio. info.

De Soto Frank