Breaking in a new engine, bores vs camshafts

That process is for pushrod engines that depend on throw off from the rods to lube the cam.

308 cams are swimming in oil at idle.

 

The rings seat pretty quick too. Using 20/50 oil or straight 30w break in oil I like to drive using not more than half throttle to around 4k rpm then slow down while in gear. The vacuum from slowing in gear helps push the rings against the cylinder walls.

 

I like a load and recovery approach. Low rpm with short moments of higher throttle then light throttle to let anything flush out. The load and rpm get high and recovery shorter until it seen redile at WOT at about the 500 mile mark. This was the owners manual procedure for a new motorcycle I had in the 90s and its how I've done everything since as it seemed to make sense.

I've also read others just beat the snot out of it on the dybo for 10 minutes and call it good....never seemed wise to me but I have no actual data so I certainly can't say it's wrong.

 

It's always a pucker factor heading to the dyno with a fresh build. However I've found that a run thru, idle to temp then shut down. Idle back to temp, then steady state each of the rpm points working to wot, works fine. There's probably a few blips in there after getting her started to feel out the rev rate. Ran one build stupid hard on the dyno for 3 days, WOT pulls etc.. took it back to the shop, tore it down and there was nothing wrong.

Biggest issue by far, low oil pressure. That'll do some serious damage to these engines. With good oil pressure they'll break in quickly, provided all other bits are done correctly.

Engine Dyno had the advantage of controlled environment and pre-heated water.

I swear I've seen video of the factory just running the snot out em off the assembly line... Maybe Brian can speak to that?

 

In the days of round rings and round cylinders thanks to modern machining and production, break in of rings is more to make us feel good than anything else. Areas of poor contact or uneven pressure are nearly gone.

 

Every engine gets 4 or 6 hours dyno time, dont recall which. Runs at or near redline for quite some time at last phase. Factory drivers regularly hit rev limiter pulling out front gate.

 

From the QV manual, much slower/more gentile than I was suggesting.
Image Unavailable, Please Login

 

What I read that seemed to make sense, and it was quite a while ago now, was that all the machined surfaces, no matter how well machined will have peaks and valleys from whatever grit that were finished with. The peaks hit and knock each other off as the part lap together, a lot at first and less and less over time. you get a lot of it at low rpm/low load in the first minutes of running and you want the oil to have time to flush it out. Then over time you push it hard with both more load and more revs until you're at WOT at redline to make sure you've got it all. There was no actual data in the article that I recall but they where suggesting 500 miles...which seems in line with the 4 or 6 hours ending with WOT throttle time dyno run you mentioned.

 

It has always been explained to me that a dyno break in can be achieved faster because of the ability to control temperature and load and run ideal and continuous speeds and loads. I have always advocated a long slow conservative process at increasing loads and RPM. I have had the best outcomes that way. I also do an oil change before it goes out for the first test drive in the interest of flushing out the debris you speak of. The biggest area of concern is rings and and cylinders and with modern tech available from the best manufacturers it is pretty much a slam dunk if done correctly compared to just 30 years ago. I just wish Mahle had a bigger presence in the aftermarket. They are head and shoulders above every other company out there.

 

I remember road tests after PDI's on new 5L mustangs in the late 1980's at the phord dealer I worked at. To say we didn't baby them is an understatement (I was young remember), even the new LSC Lincolns were put through their paces. Never had one come back with an engine issue and they only had 5 to 8 kms on them when they arrived at the dealer.

When I did the engine for my Nephews stock car, break in was 7100rpm at the end of the straight after a few warm up laps, circumstances at the time didn't allow anything else, we were concerned but had no choice, that engine lasted 3 seasons before he sold the car. He came in 2nd in the championship but it wasn't because the engine, he just couldn't make the car turn.

 

No kidding, they do some amazing stuff. The cylinder honing process Mercedes and Mahle developed for F1 engines in the last 10 years is really amazing. The cylinders are diamond shiny and smooth. Pretty much zero break in of any kind required.

 

https://www.wiseco.com/auto/wiseco-auto-blog/what-does-the-2nd-piston-ring-do-purpose-and-function-explained/#:~:text=Combustion%20sealing%20is%20100%20percent,to%20quickly%20escape%20to%20the