Some say that the rings seal better if you use a higher RPM for break-in. I read a website that explained the whole thing, and it did make sense, but I couldn't rattle it all off to you. I am guessing that would be more applicable to roller cam motors, however, because the flat tappet cam and lifters might not enjoy the same break-in procedure! I guess you could keep an old cam around just for the purpose of using it while seating the rings, and then break the other cam in later.
http://www.mototuneusa.com/break_in_secrets.htm This page I read a few years ago, it is a little OT as it's about motorcycles but has good info for the break 'em in hard crowd. A customer/friend of mine asked me how he should break in his new truck one day so I showed him this page and that what he's done, His truck works great and hes driven other trucks like his since and says thats his works better.
The reason for the high RPM is lifters and cam lobes get their oiling from oil spray or "mist". There is enough spray at lower RPM and 2500-3000 haves become the standard of the industry accepted minimum RPM for enough oil to be present during break in. What happens during break in the surface of the lobe and the face of the lifer are burnishing each other to a hard and smooth surface. This is what allows them to live without wear under loads and the lower amount of oil spray that they will see in normal use. The lifter spins to stop form having any scuffing motion during opening and closing. Once the two surfaces are sufficiently mated to each other they will now live a long and happy life.
Thanks for bringing this up hawk. I feel I know that basics but more info never hurts. I wonder how much of what we do is based on what someone else said. In otherwords, I have a tech that I work with that says he has built dozens of motors and never breaks them in other than just starting them to make sure everything is cool and then drives them and has never had an issue. Then, the guy that did my machine work it said if it cranks too long before starting it can wiper out the cam. Of course there is probably a little ass coverage from him so he can avoid being blamed for any problems. I guess in the end you do what works for you and what you are willing to sacrifice if you are wrong. I am going to err of side of caution and follow all the break in suggestions and do all the oil changes, etc.
When my dad bought his new 1964 ranchero [260 V/8-4 speed] the new-car break-in instructions said to drive the car below 40 MPH for a certain number of miles, then 50 for more miles then 60...after that it was supposedly broke in. My dad came from the "Break it in like you'll drive it" school and the first thing he did was take it to 115 MPH and leave it there 'till the road curved and he had to slow down. The Road from Bend oregon to Boise Idaho has some mighty looooooooooooong straight stretches. That little 260 ran pretty hard after that.
As mentioned earlier in the thread, I knew a guy that built engines and did the same thing; start it and run the hell out of it. I just remembered another guy who did the same. Neither ever had a problem. All the race engines I ever built, rebuilt or replaced the cam in I would do a proper break-in. My neighbors didnt seem to mind. Also stated earlier; if you replace the cam you should use new lifters or if you remove the lifters keep track of which lobe they are mated to. Ive done this and had no problems, but Ive also just threw the used lifters in a bag full of oil and when I got ready to use them I just put them in the engine along with the used camshaft. No problems there either. Now Ive only dealt with SBCs and a small number of camshaft manufactures, maybe the companies build better products, the lubrication today is better or I just have good luck, which I doubt. I guess it comes down to what you are comfortable doing and if you do have a problem accept the consciences. Great topic.
The problem with breaking in an engine at high rpm's that are constant is it wont seat your rings properly. It takes not only compression on acceleration, but also on deceleration to seat the rings well. If you don't vary the speed (after intiaal cam break in) during ring break in you will end up with an engine that smokes when you decelerate. I've always broke in engines I built by constantly varying speed, and downshifting when slowing down. Never had problems seating rings using this method.
Think someone was exaggerating a little there. If you look at magazine road test from the day, a 65 Mustang, which is more aero than the Ranchero, with the 271HP 289 GT option would only hit 117 MPH. I doubt the 164 HP 260 in that Ranchero would come within 2 MPH of that.
You break in parts for the same reason you date before you marry. Still not a guarantee you won't wear it out or blow it up, but at least you know it works for the time being. I'm no engineer, but I know if you look at freshly machined parts under a microscope they look like the surface of the moon. Break-in helps to smooth the surfaces from the rough parts so they can glide together better for the long run. Another term for break-in is "wear-in" for that very reason. I'll assume the parts could be micro-polished before assembly and break-in wouldn't be as important, but imagine the costs outweigh the benefits.
I've spoken to an old buddy who was a factory mechanic for Chevy, and he tells me of all the engines he built back in the day, not a one was started and held at 2000rpm for blah blah.... It seems to be something that has surfaced in recent years/decades as oils lose their content and maybe metals get cheaper and machining gets quicker and less accurate. Afterall, running in an engine is done because the machining is simply not done close enough to start with, the finished not five enough. Modern cars don't nee any running in.
I had a really original 1960 Ford Fairlane and it had engine break in instructions on the back of the glove box. "do not exceed so and so loafs" "hold at 2000 loafs" or something like that....i remember they used the word "loafs" instead of RPM
After I started reading this, I was wondering if anyone would get to these points. Every instruction sheet that has come with any cam I have broken in has stated to vary the rpm a few hundred every once in a while during break in. The reason is that the oil spray/mist, as hotrodon mentioned in the above quote, might be heavier on one part of the cam and not enough on another part when using one set rpm. By varying the rpm the oil is thrown around more for better oiling. Once the cam is broken in, the normal mist of oil is sufficient.
So when I build a complete motor, how do I know everything works before cam break in? Like carbs, timing and everything? Should I just run it for a little bit to make sure it runs good and then break the cam in? How much time do I have before I mess anything up? Should I just try to get it close?
Your friend's car was ready to run fast sooner. Lucky his dad was a dealer, he could get a new motor under warranty if necessary, and as he traded every year he did not care how long it lasted. A carefully broken in motor would have been faster once it was completely broken in but this could take 5000 miles. It would probably have gone many thousands of miles farther before wearing out.
They built them mild, with mild cams and soft valve springs so breakin was not as critical as in a hot rod. PS did you ever wonder why the most powerful performance models were sold with NO warranty?
You know the carb is right because you rebuilt it, or bought a new one, or it worked great before you rebuilt the motor. Only slight idle adjustment necessary. You know the timing is right because you set it right. You know everything on the motor is right because you checked it at least twice. Never mind the hillbillies who throw a motor together then fart around with the carb, twist the distributor like a doorknob, and hope it stops blowing flames out the carb and starts running. Just put it together right in the first place.
I see where you're going with this. So I'll either be alright, or find out that I shouldn't have done the rebuild myself. Lesson learned.
I wish I had a buck for every person who told me that something was right because they double had checked it themselves..... Lucky for us Hambers, we never make mistakes or errors.
I double checked everything on the last motor I built an it fired right up and ran great! Held it at 2000RPM for about 5 minutes and then realized I was so focused on having the engine perfect I neglected to double check the level in the P/S pump. Held it at 2000 for 15 more minutes and literally smoked the P/S pump. I was lucky it did not seize and sling the belts. Live and learn....double check EVERYTHING!...and then check it again!
I can't imagine the whole process is so fragile that you'd smoke the cam just by shutting it down and restarting it during this 20 magical minutes. If that's the case then something is wrong with this whole idea, somebody is missing something critical somewhere.
Point was to pass on a story to help others not make the same mistake I did. If I had double checked EVERYTHING I would not have put my self in that situation
Put some water in the rad too lol have seen that forgotten in the excitement. It is possible to forget something or do something wrong. But if you tried to put it together right, time it right etc. you will have less things messed up and a better chance of finding the problem.
The Jalopy Journal
