Break In Method: Hard or Babying It?

[P-Tree]

I'm curious about everyone's opinion on the break in method debate. Some swear by the hard break in, others swear b taking it easy for up to 1,000 - 2,000 miles O_o

I'm in the hard break in camp. Everyone I've personally known that has built cars, and even stock cars, that took it easy on the break in / hardly ever lay into it, has issues. Blowing up turbo motors, oil bypass, smoking, etc.

I did a hard break in on the GT350 and the GT-R. Hell, I hit full boost at 28 miles on the GT-R, and did launch control at 30 miles. I was supposed to wait until 1,500 per the manual...yea, that wasn't happening! I went to 8.8k rpm WOT with the GT350 with 20 miles. Both of them, no issues at all. I say beat on it as soon as you can! Some people mistake this as I turn on the car, and then go WOT. That's not what I'm talking about. I take it easy until the fluids are warmed up, engine and transmission. Once she's all warmed up though, that's when you can have some fun! (take that as you may). I'm not over revving, abusing the transmission, etc, but I am using the engine as designed! Pretty famous example is all the people who went easy on their RX-8s, the engines blew up on them. Not apples to apples here, because it's a rotatory, but you get the picture.

Team Hard Break In!

Anyways, I know people have strong feelings on both sides of this argument. What's your reasoning / thoughts?

[Milliwatt Rob]

Today's machining of parts make them fit together better from the outset than was the case 50 years ago. But one thing that happens in break in is that parts are subject to heating and cooling cycles. Heating and cooling cycles relieve internal stresses in metallic parts. Varying the throttle settings results in heating and cooling of internal parts.

Manufacturers recommend reduced max rev limits in new vehicles. Which is why the C7 tachometer had the reduced red line at low odometer readings. I assume its for a good reason, and not a holdover from ancient automotive folklore.

[Mobius]

I follow the manufacturers recommendations, relative to max RPM versus miles. I've done this since my first new Suzuki GS750 at age 17, and I've never had an issue.

I expect that the C8 will have the maximum redline displayed on the tach for the 1st 500 miles, just like the C7 did.

[John]

Thanks Mobius for posting that video! Having had 50 new vehicles, and always following manufacturers recommendations without a single engine issue, I will again follow GM’s recommendations for breaking in my C8.

And BTW, it is not just the motor, for when I talked with C5/C6 Chief Engineer Dave Hill, he said that his biggest issue was not the motor, but the diff gears being properly being broken in. I can not 100% remember but is it not 1,500 miles before GM recommends track usage. Along that line, Spring Mountain always puts 1,500 street miles on their car before allowing them onto their track.

[Racer X]

And that's why I would never buy a used sports car...

(with the exception of John's C8 Stingray)

[Racer86]

The gears need to burnish the teeth to kind of polish the high spots off with out a lot of heat. If you hammer the gears when they are new, they can get overheat spots on the teeth and draw the temper out of the metal. We were taught to not use constant throttle, vary it to allow the gear teeth to
“get friendly” without building up heat.
best bet, go easy for the first 500-1500 miles. Don’t drive at a constant speed, shift once in a while.

[John]

Great specific Racer86. Another thing I do is a fair amount of engine compression breaking during the first 500 miles, doing the varying throttle that Racer86 just mentioned. Here’s my process (and I admit there are a lot more fun things to do).

When my motor is fully warmed up, I take it in second or third gear up to the 4,000 initial RPM limit, then let the motor’s compression slow it down (isolated country road is safest/best), then when the compression has reduced its RPM’s to 2,500, I do this again. And then a third time. I do this once every 15 minutes during my hour drive. Then I go home and let is do a complete cold soak. Probably do that process ten times during the first 500 miles.

Why?

When the engine does compression breaking, that adds additional oil to the bottom side of the rings, helping them best seal against the cylinder walls. And for those who want best power, best fuel economy, and lowest oil usage for the life of your motor, that is a literal win, win, win situation.

However, might the LT2 has specific oil squirters (as the LT4/LT5) do that reduces the need for that breakdown process???

[meyerweb]

I really don't think I know more than GM's engineers do. Or any other auto manufacturer's engineers. I'm not aware of any manufacturer or engine builder that recommends beating an engine hard right out of the box.

[Boomer]

I really don't think I know more than GM's engineers do. Or any other auto manufacturer's engineers. I'm not aware of any manufacturer or engine builder that recommends beating an engine hard right out of the box.

Yes. I follow all OEM recommendations regarding break-in and everything else. So far it seems "Team Hard Break In!" hasn't gained any new members

[Frenzy36]

Always follow manufacturers break in procedures. As John has properly described. As far as the rings seating these days most engines are built with plateau honing which doesn't require such critical break in procedures as years ago. Somebody would have to confirm that GM Engines follow this type of procedure as I am not sure.

[Racer86]

Always follow manufacturers break in procedures. As John has properly described. As far as the rings seating these days most engines are built with plateau honing which doesn't require such critical break in procedures as years ago. Somebody would have to confirm that GM Engines follow this type of procedure as I am not sure.

On the Dyno, we find that with current cylinder hone finishes and current piston rings that they seat very quickly. With roller cams, the breakin time compared to flat tappet cams is much shorter. In the “old” days the first few minutes of break in time on a flat tappet cam was critical, and you could ruin a cam lobe very quickly.
on the gear deal, remember that the gear tooth has 2 sides, that is one reason for varying the speed so both sides of the gear tooth can get friendly without generating a lot of heat.

[Mobius]

I really don't think I know more than GM's engineers do.

We all agree with your self-assessment.

[Racer86]

Great specific Racer86. Another thing I do is a fair amount of engine compression breaking during the first 500 miles, doing the varying throttle that Racer86 just mentioned. Here’s my process (and I admit there are a lot more fun things to do).

When my motor is fully warmed up, I take it in second or third gear up to the 4,000 initial RPM limit, then let the motor’s compression slow it down (isolated country road is safest/best), then when the compression has reduced its RPM’s to 2,500, I do this again. And then a third time. I do this once every 15 minutes during my hour drive. Then I go home and let is do a complete cold soak. Probably do that process ten times during the first 500 miles.

Why?

When the engine does compression breaking, that adds additional oil to the bottom side of the rings, helping them best seal against the cylinder walls. And for those who want best power, best fuel economy, and lowest oil usage for the life of your motor, that is a literal win, win, win situation.

However, might the LT2 has specific oil squirters (as the LT4/LT5) do that reduces the need for that breakdown process???

Oil “squirters” aim oil on to the bottom of the piston dome. The main use is to cool the piston dome.

[meyerweb]

And engine braking helps load the rings, and other internal components, in both directions. That's beneficial for the same reason Racer88 mention in connection with loading the gears on both sides of the tooth face.

[Boomer]

Oil “squirters” aim oil on to the bottom of the piston dome. The main use is to cool the piston dome.

I guess as I slow down that happens?