The Stovebolt Site Forums The Shop Area Engine Shop Fresh rebuild break-in

Wondering what the proper breakin tme would be for a freshly rebuilt (everything, rings, bearings, cam & lifters, valves, the works) before running for extended use at highway speeds (60-65)? I'm not talking about initial run for breaking in the cam an such, I want to know how many hours/miles the engine should be run at varying light loads before considering it ready to be driven as normally. The motor in question is of course a 235 bolt of 1960 vintage.
Your advise and wisdom ar greatly appreciated.

Chuck

chuck,

once you establish a proper cam break in, you should be good. The only other thing that will happen is with your rings it might take a couple hundred miles to set them, depending on which kind you have used. Sometimes you might have to retorque your head, some people do some people don't.

That is similar to what I would expect. I have been told first 500 miles to "go easy" vary the load with no sustained high rpm runs for more than 8-10 miles and to watch the temp gage as the new tight motor will make more heat until the rings have a chance to seat in well. (I assume due to higher friction of the new rings in the bore.) I had a friend who neglected to follow this advice with a 235 that was also rebuilt, with only 4 miles on it after the initial cam break in he jumped on the highway for a nice 1 and a half hour cruise to a friends place. Non working temp gage. Overheated it, really hot is my guess, and by the time he knew what was happening he had taken out the bearings. Had to have the crank ground and replace the mains, rod and cam bearings, and I think have the rods resized.
I'm thinking better safe than stupid so I'm asking the experts.

Chuck

...short drives to the icecream drive-in or a couple short drives "in the country" should be in order first to establish all components are working and the cooling system and temps seem to stay "normal".


...but then of coarse, I have let them run long enough to adjust the valves and then as my brother would say "go or blow". I don't recommend that but we've done it quite a few times!

I like to get 500 miles of driving time with different speeds and making sure not to lug it or over rev it. Then get the oil changed and double check bolts, hoses.

I am in the 1500 mile camp.

Can you explain the cam break-in...is that just slow go or what?

Cam break-in: Upon first start of engine, run non-stop at fast idle for 20 minutes. On V-8's, I usually run at 2000 rpms. Maybe not so fast on the stovebolts, but not sure.

IMHO, the morst important part of all of this is that the oil should have a high zinc content (ZDDP maybe?) or an equivalent break-in additive to the oil. Valvoline racing oil has ZDDP in it.

We finished a round track engine installation less than an hour before qualifying time several years ago, so I put one of the pit crew guys in the car as we trailered it to the track so he could keep the engine running at 2K RPM for the cam break-in. 30 minutes later the driver backed it off the trailer and hit the track for the time trials. That one was one of the best race engines we ever ran. Of course, a brand new round track engine has more clearance built in everywhere than a 100,000-mile street engine has, and it's totally worn out after less than a thousand miles of track time!
Jerry

We used to break-in our engines in the water box at the drag strip! If it made it through that, which they did, it got one easy pass. The next race was all out.

Street engines need a little more then that, very the load on the engine, run it up in rpm and let the weight of the truck slow it back down, then go again. Do it five or six times out on the road, third or fourth gear. After that give it some miles, your choice. Change out the break in oil when you decide its dirty enough. I like to leave it for a few hundred miles with one filter change in between. Good oil cost more then filters!

Dad used to go down to the GM Fairfax plant in the late sixties and watch GTO's come off the assembly line. They tried to see who could get longest burn outs coming out the doors of the plant! There was no going easy because they were new!

Joe

Joe/Jerry is right. Break in is all about what you have or how you built the engine.

Jerry you and Joe sure bring back memories for me. When my brother finished building a racing engine I could hardly wait till it was on his dyno. Man, how he would twist those engines. I remember once I told him, on an experimental engine that I believe it was enough and the engine was begging. He said "go or blow". Good Gosh, you should have seen the pieces flying around inside "the torture room".

Joe, back in 65/66 I worked at Poole Chev. in Gaffney and I serviced most all new cars from Corvairs to Corvettes. Back then the dealer(my job)had to put in the carpets/hub caps/ checked engine ect ect and then ROAD TEST them. That called for a trip down the "draytonville straight". I sat in some fast cars and two always comes to mind. A special built 442 old with two fours and a special order stingray. I still remember the feeling. The Corvette "scared me" before I ever got it in fourth gear good.
Those were the days.

..... didn't mean to hijack the post. Just sweet sweet memories!!! Let me tell you about a Corvair Monza.........

It mostly comes down to drive it normal with out getting to high of rpm for to long of time. The cause for worry is the first start up and cam break-in. Lube, lube, and more cam lube is the key! Use good known break-in oil, not to heavy (10-30, 10-40), zinc additive if the oil is not made for break-in, and keep it cool! Once started, get the rpm up ASAP and leave it, 15-20 minutes. Dial in the tune up after!

How many new rental cars you think were run hard!

Joe

Do NOT baby it. Like the others have said, do not overheat it and vary the speed, but you HAVE to put your foot in it. You really should do several full throttle pulls up through the gears after everything is up to temp. Cylinder pressure is what pushes the rings against the cylinder wall. The higher you get the cylinder pressure, the harder it pushes on the rings. If you baby it, it can take forever for the rings to seat. Using this procedure you will get a better ring seal as well, which means more power!