shoedoos wrote:engine rebuilt, new hydraulic flat tappet cam, new rings.....running the cam in for 20 mins (or whatever period of time) with the rings unloaded....what's the best way to ensure they bed?
The best way would be don't replace cam same time as rings, and/or break it in with load on it.
I don't personally see why you have to break in a cam with no load. In fact the way I read the instructions.....it does not really say you can't.
I always just drive a new vehicle like I'm going to drive it every day, and change oil after 1000-1500 miles (whether the manufacturer advises it or not). I've had 2 vehicles go 100k+ with no consumption doing it this way, so I would agree that nothing special is required.
IF it needs any appreciable break in, which it shouldn't need, it needs some time with a bit of load. Build some cylinder pressure to get good ring wall pressure to seat them in with the cylinder bores. Do some accelerations and highway driving. But i'm with the others, it likely will not need any at all.
Years ago my dad was building himself a hot street motor to put it in an old pontiac. He always had arrogant level confidence in his engines. He kept telling everyone, "I'm gonna back it out of the shop and put it to the floor". He wasn't kidding. Smoked the tires down the block. Not a wisp of smoke (from the engine anyway!).
I had two nearly identical 95 Toyota Corollas. My wife bought the first one with 10k miles on it from a local dealer just before we met. I always used Mobil 1 oils and changed it yearly at about 12K miles. When gas prices went up I started looking for another corolla and found one that was bought from the same local dealer at the same time my wife bought hers. I think it was around 2002 when I got the second car. My wife's car had accumulated about 250K miles and the second one had accumulated about 180K miles. The lady I bought it from said the oil was changed regularly with conventional oil.
Wife's car with 250k used minimal oil, 2nd car with less miles used significant oil. So, after owning the second car for a year or two and driving it about 20K miles I yanked the engine, pulled the head, and took it all to a well know Nascar shop to get the machine work done. The machinist/engine builder looked at the bores and said we could really get by with reringing it, but I said no, let's do it right and bore oversized. I got the parts from Toyota and took them to him. After boring he called me and said "do you want me to go ahead and assemble the short block for you?" I said " I guess so, but don't put the head with the 5 angle Newen motorcycle type valve job back on because I want to say I " rebuilt my engine". A day or two later I picked up, bolted the head and accessories on, cranked it drove it like he said to break it in, and enjoyed it until today with over 100k miles on the rebuild engine. IT HAS NEVER USED ANY OIL since the rebuild. I love my car. Always used Mobil 1 since I got it.
A few years later, my wifes car finally starts using significant oil after 320,000 miles if I remember correctly. So, back to the same shop I go, buy the same Toyota pistons, ring & bearings, same machinist on same machines, ONLY DIFFERENCE, I ASSEMBLE THE SHORT BLOCK. When I had the short block together I called the machinist and asked him if It was ok that I got some of the green assembly lube in the bores (Federal Mugul stuff from a 2.8 truck engine I build years ago). He said "Not really, you need to get that crap out of there". I don't remember how I went about "getting that crap out of there" but that engine used oil, maybe a quart every 3k to 5k miles, until the car was totaled a couple of years ago. I guess I will always wonder if I put the second rings on upside down or if it was the green stuff in the bores. It still kinda bugs me.
It is also possible that it uses oil for some odd reason, not even related to the guide clearance or rings.
I've had several cases of that.
Customer brings in engine to be rebuilt, often easy job.
Then when they get it installed and broke in ect, they complain that it uses oil and/or leaks exactly the same as before.
Because the cause is some odd defect like a porous spot in a casting, or a leak caused by some housing that does not fit together right, and not something that is a wear item, not something you would ever look for unless you knew what you were looking for. In some cases, they MADE it that way, and it was probably like that all along!
Well, it would have been nice if they had mentioned specifically what the problem was, which they usually don't.
If it's new to them, they probably don't know anyway,
Now if I don't find a problem, I worry. Doesn't happen often but it does happen 1 or 2% of the time.
I was a mechanic at a chevy dealer for a couple years back in the late 1980's. Part of the new car prep was to test drive car. We were instructed to drive easy at first, until full temp, then run it up the local long up hill stretch of road as hard as we dared without crashing or getting arrested to break in the engine .
That was my MO to Bill , and I see nothing wrong with that because your just compressing what use to be a 500 mile long low rpm break in down to 1 or 2 full throttle blast!
You can cut a man's tongue from his mouth, but that does not mean he’s a liar, it just shows that you fear the truth he might speak about you!
A friend of mine told me a funny story about a guy he worked with who bought a brand new Harley Davidson motorcycle. He said that guy pampered that bike, never giving it full throttle etc for probably about a year. He said that he harped about break in being very important. One evening my friend saw a show on TV about Harley Davidson motorcycle production and how they are built. Anyway, at the end of the assembly line there was a guy there who would start each motorcycle and then proceed to take it to the rev limiter in every gear on a roller dyno! The thought was that if there's a problem they would like to find it at the factory and not after the customer owns the motorcycle. He said he couldn't wait to tell the guy...
