Is it true that one can't run a car any faster than 30 miles per hour after it's engine has been rebuilt?

Question

I did an overhaul to my 1993 Nissan Pickup, but I was advised not to run the car any faster than 35 miles per hour before the Engine has at least ran for 500 miles atleast. Is this a true myth or just bullshit?

Answer 1

depends on the material used in the rings/bearnings and level of finish of the bores.
in the old days these were done roughly using soft iron rings, meaning he engine needed a break in period. with modern materials and techniques this haqqs been reduced to almost zero

Answer 2

Not quite! But it is recommended that you don't go out and run it at 70 right away! Rebuilt engine is using "non-detergent" oil which makes the rings wear- (or seat in" faster). As engine runs, it generates more heat due to friction on cylinder walls, so running it too fast, may harm rings by overheating them (engine cylinders too).. in the "old days" cars had temperature gauges that told you what actual temperature was, - now a lot of them have "ididot lights". If the engine was running too fast it would raise temperature a lot, - which let you know that it was time to slow down a little till it was nearer to the "normal" opearating range! Also it is better to run the car a little faster for a mile or so, and then slow down for a mile or so,- once in a while. I would guess that the 30mph would be for first 10-20 miles, by then it shoud be on it's way to having "matched" the rings to the cylinders! With gearing on newer cars, thirty mph does seem a little slow though, I would think more like 45 after 10 miles or so would be ok!

By the time you have a couple hundred miles on engine you should be pretty well "broken in" , unless you have really hard chrome rings installed, they take longer to break in. Mechanic will tell you when the engine should be about "broken in" and want you to come back and get the oil changed. Also by then you should be able to drive regular road speed for short distances without harm.

Answer 3

First, engine RPMs are what matters, not MPH. Driving it like you stole it isn't a great idea, because many tiny bits of metal come loose during the first 1000 miles of driving, and you don't want those flying all over the place. For the first 1000 miles, drive normally, with periodic bursts of acceleration. This doesn't mean floor it and run it to redline. After driving long enough to bring the engine up to operating temperature, go out to a back road or highway, and give it enough gas to downshift and accelerate for about 10 seconds. Basically, you don't want to run the engine high in the RPMs, but you don't want to leave it at one speed the whole time. Change your oil at 1000 miles, or 500 and 1000 if you're really cautious, to get those metal particles out. Also, don't do any heavy hauling or towing during the first 1000 miles. You don't want to screw up a new engine and have to replace it after another 20,000 miles.

Answer 4

ENGINE RPM IS FAR MORE IMPORTANT. IF YOU CAN GO 50 AT 2000 RPM, GO FOR IT. BUT IF YOU TREAT IT GOOD NOW, IT'LL TREAT YOU GOOD LATER. AN OIL AND FILTER CHANGE AT 500 MILES IS A GOOD IDEA. 90% OF THE WEAR THAT ENGINE WILL EVER SEE WILL OCCUR IN THAT TIME FRAME.

Answer 5

wow they let you type bullshit?

uh yes and no. ok look.
you just paid that money to have this done, baby the damn thing for 500 hundred miles. its called the break in period. whats happening is everything is finding its groove again. thats no bullshit, the parts are literally doing just that.
take it easy with it and enjoy new motor for many more miles.
myth = true
~Steve

Answer 6

drive the heap... breakin should have been done before you picked it up