BUBBA

Breaking in my new short block. Most manuals say just don't exceed 55 MPH for first 500 miles and vary your speeds.

My mech. just told me to keep the RPM up between 1700 and 3000 for the first 500 miles.

For the first 100 miles so far, I drove straight through keeping my engine mostly around 2000 at around 65-70 MPH in 6th gear and once in while running it up to 85-90 in 6th at around 3000.

I would think the RPM is the most important.

Give me your opinions on how I should drive the next 350 miles of breakin.

I hope I didn't do bad by running it up past 55 MPH.

Mikey97Z

I would say that the RPMs are more important than MPH, but also stay out of 6th gear because lugging the engine is hard on the bearings. Maybe that's why he said stay under 55 MPH.

Injuneer

He should also have told you to vary the RPM frequently, and not to hold it at one specific RPM for an extended period of time.

BUBBA

Actually, the mech. didn't tell me to keep it below 55. I just read that in the manual.

I have 4.10 gears so it really isn't lugging in 6th gear. I'm running around 2k in 6th at around 65-70 MPH.

So Injuneer, etal, you believe that the RPMs are the most important part as long as I vary them and do not go beyond around 3k for the first 500?

I don't see anything wrong with going 90 if the RPMs aren't too high. It sure started to get loud around 80 though. I hope it's just the engine noise and not something else.

The 97 DS is supposed to be OK, but maybe that is where the loudness is comming from???

chasmanz28

Before 500 miles:

Try not to exceed 55 mph for extended periods of time
Do not go on long trips and keep the car running at the same RPM, try to vary your RPMs
Do not do any hard launches on your car
Do not let the car sit idling for long periods of time
When starting the car cold, let it warm up a minute or so before accelerating hard
When you car hits 500 miles, you should probably change your oil. Most people stick with regular "dino" oil for the first oil change.

IrocManiac

I say RPM's are WAY more important then speed. The 55 mph rule was come up with by using a specific gear and other things that are widely variably from one car to the next. 55mph in one car would be 1300 rpm, while 55 mph in a car with 4.10s or 4.56s could be 2400 rpm or whatever the case may be. I say the 1700 to 3000rpm sounds about right. Thats what we did on my friends truck (1500 to 3000) and its a runnin' machine now. Change your oil after the 500 miles like chasman said.

BUBBA

Thanks guys. I can't wait to get the thing broken in because I need to figure out why it sounds so damn lound around 80 MPH.

I just had 4.10s put in, but I never noticed anything noisey with them before the new short block.

And since I never drove the thing faster than 75 MPH since new, I don't know whether the noise was there before and/or I happen to have an unbalanced DS. However, the DS problem was supposed to have been fixed for the 97Lt1s.

Thanks again for the replys.