How long on break-in oil ?
 

I am currently in the process of running in my newly built 3.2SS engine. Bored and replated carerra cylinders and new CP 10.5Cr pistons. 6 new rockers on my already used cams and new rod and main bearings. I have Motul 10W-40 Break-In oil in there now, and have been driving it as hard as possible on public roads for some 350 miles the last week without being stupid, so not hard but not babying it in any way and avoid very high rpms. I and would like advice on how long to run with that oil before I change to synthetic ? Is it an oil that can be used for some time ? Viscositywise it gives good oil pressure and engine runs nice

It still smells of oil occasionally but no visible smoke and I have not registered usage

Having read maybe 1000 posts on oils here on the forum I find that not only do I still not know exactly what to do. Not only that but I also feel nervous regardless what I do wrt oils. One reason for that is I have had issues with abnormal cam and rocker wear before that may or may not be oil related...

no advice on this ?

I changed out the break in oil on mine after 300 miles

Not long!
After the rings seat. 500 miles or couple hours.
This depends on how you go about it.

oil still looks transparent and light golden and rings are still not sealing (some oil smell on liftoff, no smoke visible), after now 400 miles.

I'll give a bit longer, after all 12 quarts is a large volume

Hope you read how to seat rings?

Rings should have seated within the first couple minutes of running the motor. You can see it happen; smoke and smell and then suddenly nothing.

What you are smelling is not rings; if it was, there would be smoke all the time. Most likely a leak or something. Even old spilled oil on the headers takes time to dissipate.

Has it burned any oil in that time frame? I would not panic if it hasn't burned much or any oil in 400 or so miles.

We do a one track race day break in - about 100 miles - and drain/replace with normal race oil for the next day. You might consider replacing your break in oil now . . .

Did you do the 20 minute high idle break in first?

Your cam wear may be caused by incorrect warm up during normal daily driving - need to
high idle - 1500-2000RPM until 180F - we had this cam wear problem too and were told the correct method by our cam builder.

Regards,

So break in oil is essentially blended with zinc for elimination of wiping damage which is what happens with aftermarket cam related problems. Why would it do harm to run its course if it has just been returned to its non emissions base.

regards

Trond, change the oil now, you will be OK.

350 miles
figure 846 revs per mile with 225/50R15 tires, that's 296,100 rear tire revolutions

Assume 8:31 ring and pinion, for each 8 turns of ring, pinion goes around 31 times =1,147,388 pinion revolutions.

Now, the speed limit around Stavanger (I was there two summers ago, one of the most beautiful places on earth) is nominally 110Kmh, or about 68 mph. Assuming you were breaking in the motor by flexing it up and down under load (always a good idea) then I guess you were in third gear most of the time. Stock third gear in a 915 is a 23:29, which means for every 23 revolutions of the pinion you need 29 revolutions of the input gear, or 1,446,706 engine revolutions.

SC stroke is 70.4mm, and that distance is covered by the piston twice per revolution-- once on the way from TDC to BDC, and then back to TDC. So with each rev the piston moves 140.8mm. So in those 1,446,706 engine revolutions, each piston moved 203.7 kilometers.

I think it's probably broken in by now. :)

Bonus: 350 miles =563.27Km. If you were at the maximum speed that driving took 5.12 hours, or 307 minutes, or an average RPM of 4,708! Way to rev that thing (theoretically!) :)

Thanks for the advice and love your assessment there 304065

Yes I did the 20 min 2000 rpm routine first, then changed to current 10w-40 Motul break-in oil. And yes I have been flexing its muscle and not babied it. Was thinking a 10w-50 synthetic but could be early for the engine? It is running very nicely btw. The added torque with larger bore, higher compression and dual spark was just what I was looking for.

I’ve just gone through my 3rd rebuild, not one engine builder has used a specific break in oil.

The first two used dino/mineral oil (15w40) for the first thousand miles, the 3rd has filled with an SL rated ‘synthetic’. I may yet ask him to swap this out for a mineral, however retaining old p&c/rings, there has been no specific break-in advice provided, aside from not holding it in a high gear for too long, or loading the engine in too high a gear.

Trond - i recall your initial post about your abnormal rocker wear which you thought may be viscosity related? Good luck this time round!

thanks sp_cs. Unfortunately my previous issues combined with reading every single oil related post has led to a state of paranoia. And combined with the investment in time and money in my rebuild.... not good.