What weight oil for first time start up?

[yellow85cj]

Getting ready to start my rebuilt AMC 258 i6 / 4.2l for the first time. Other that adding a break in fluid, what weight oil would be best for start up/break in ?

 

[mtnwhlr]

I used a 10w30

 

[Joebronco]

Crappy 10x30 for break in.


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[Lumpy Grits]

I would be asking the engine builder this.
Most of the time this is printed on the workorder/reciept.
LG

 

[Belizean]

I would be asking the engine builder this.
Most of the time this is printed on the workorder/reciept.
LG

X2. I haven't got that far yet but the shop that machined mine said to use a special break in made by Joe Gibbs Racing or equivalent

 

[Lumpy Grits]

Not only is the oil very important.
So is the inital engine start and run up.
PLZ-Ask this builder how they want you to do this. You don't just start the engine and drive it. You have rings to seat and lifter breakin to work on.
LG

 

[yellow85cj]

Builder didn't spec anything but the Comp cams break in additive. Been thinking of using Shell Oil zinc additive with oil. Also think of using it with future oil changes. Only thing about using it regularly using it, is that high zinc oils supposedly cause premature cat converter failure.
https://www.shellx100oil.com/classic-motor-oils-additives

 

[dukecharmary]

My engine builder/machine shop instructed me on initial start up and break-in for my rebuilt AMC 258 i6 / 4.2l with 4.0 head and crane torq cam.
1. Use the high zinc additive in a name brand non-syn 30W or 10w40 oil.
2. Prime the oil pump prior to start up, making sure all valve rockers have oil flow. This will insure oil to the camshaft/lifter surface. Very important!
3. Set timing very close to ensure a quick start.
4. Run engine to operating temp while getting ignition timing set then let cool.
5. First 500 miles no hard acceleration or pulling. Vary speed as much as possible. First couple of trips 5 miles or so then let cool if possible. Good for ring and pinion break in too.
6. Change oil and have fun.

 

[slomo]

Some good advice given about a new engine. Don't forget STP oil treatment which is high is ZDDP.

What about a broken in motor? We still can use products like STP. We all are running flat tappet cams. Today's oils strip all the old school cam/lifter savers out. Good idea to dump half a bottle of STP in at every oil change. Save your cam and lifters.

slomo