big dave

I just recently installed my heads and cam onto a rebuilt stock bottom end. How many miles should I put on the motor before I can really get into it? Are there any other break-in procedures that I should be aware of? Thanks for any help/input you guys can give.

ZDriver96

just asked this question.. But i like to drive the car back and forth from the parts store so while **** is breaking i can be at the parts store to pick it up or be home to put it on

No basically you should start it up... hold the revs high like 2-2.5k rpms serveral minutes... Then take it out and drive it and make sure to keep the rpms up and vary them up and down up and down. This helps everything seat properly.. Change the oil after 30-50 miles to make sure nothing odd is in there.. Then drive it pretty much normally but still try and jump the rpms around some..

I have 170 miles on my break in. I got on it some last night.. I did not take it past 6000rpms (red line is 6400) and i did my hard accelerations in 1st gear so as not to hold the rpms too long.. I basically justed wanted to feel the power again and get the engine use to running. Felt good.. know i need a tune though. Ill probably switch to synthetic at 300 miles intead of 500 cuz i want to get the car dyno tuned soon.. and i dont want to be running it hard on the dyno without synthetic. Everything is pretty much done at 100 miles and then drive it normal for a few hundred more to make sure everything checks out.. thats my opinion.. works fine so far.

WS Sick

I allways drive variable speeds and RPM, I usually don't redline it for that first 50 miles or so. But as soon as that breakin oil is changed and you know it isnt going to fly apart its time to let er rip.

My favorite method to get the rings to seat is to take it onto the highway and accelerat about 2/3 throttle to 60 then slow er down to 30 then repeat several times, the smoke out the pipe usually disappears by then.

If its a roller cam you dont have to hold it at RPM immediately after the first start-up, but if its a flat hydraulic cam you need to hold it at 2k to 2.5k for a good 10 minutes or so to break in the cam. Hydraulic rollers dont need this breakin period.

Mindgame

~15 minutes of varied driving and you're good to go. That's if the bores are good in the first place. Yep.. need to change the oil as these gents suggested.

-Mindgame

Compstall

Hold the gas pedal to the floor and start the car. Once it starts, and the valvetrain is screaming for mercy, slap'er into drive.

WS Sick

I like the catchpan that I use below my engine stand to be in place when I do this method, that way clean-up is much easier.

magius231

as above, roller cams do not require the breakin that flat tappet do, so forget the hold it at 2kRPM for 20 minutes or whatever. There are a few schools of thought about this one...personally I waited 500 miles before I stomped on mine, and try not to drive at a constant RPM for too long, I. E. no highway trips. Motor was fine when I got rid of the car.

My machinist however broke his last 500+ HP engine in by planting the front end of the car against a pole and doing the longest burnout his tires could take. Again, motor still running last I heard

big dave

Thanks for the replies. I do have one more concern. I changed over to a slightly larger cam and noticed that my scanmaster was showing 850 (mv/uv?) after a 3/4 throttle launch. My duration is the same for both cams (222/230) but lift is higher for the new cam (.542/.563) -vs- (.533/.544). I don't think my o2 sensor was reading this low with the old cam so why would it change with this one. I spoke with a programmer who said that programming shouldn't be necessary as long as I'm running the same duration for both cams. Shouldn't my o2s be closer to the 920s?

WS Sick

Well under WOT the low 900s to high high 800s are acceptable with a natuarlly asp, motor, does it show any knock?

Big Red Jim

You're better off using 3rd gear than 1st for seating rings. The biggest key is to vary RPM and load for the first 1-200 miles. Change the oil, then give her hell

magius231

please don't try to use the stock narrow band O2 sensors for tuning...the sensor is not fine tuned well enough to handle it and the farther away from 14.7:1 A/F you get the less accurate it becomes. Get a WB O2 on there or get it to a dyno.

big dave

It's not showing any retard. I've seen the scanmaster flash 2 degrees on occasion but then goes right back to 0. Today, the check engine light came on and I noticed that the left 02 sensor is very inactive. In fact, it only registers in the 400s now. My BLMs are showing 160 on that side. I checked for vacuum leaks but could find nothing wrong.

Derrick Redd

Sounds like that left 02 is RIP. If it stays at a constant 400 and doesn't move, change it out.

big dave

I think you're right but should it have an affect on the BLMs?