I've read a few posts telling about breaking in a new cam and lifters,running the engine for 15 min or more at 2000 rpm,is this for new cam ,the engine already broken in or is the a new cam and a fresh rebuild. In my career as diesel mechanic, I have dynoed and broken in at least a hundred engines,we went to great lengths to idle these engines as little as possible,just enough time to make. Sure it ran ok and had no leaks.it was set up on dyno and put under lite load until warmed up and then run a varying loads and rpms until broken in.is running a fresh rebuild at fast idle no load not asking for glazed cylinders?
In "general" the conversation here has been to follow the break in procedure for the cam and lifters. Fifteen minutes is not a long time. My brothers and I use to get it started and run it up for about 15 minutes, run through the valve adjustment, then back them out in the highway and try to stand it on its back bumper! Not telling you to do that but if you have a new cam/lifter set it would be a good idea to follow the procedure in my humble opinion.
There are two break-in procedures, one for cams, another for rings. The 15-20 minute fast idle procedure is to establish a running relationship between a flat-tappet cam and new lifters. Roller lifters- - - -no problem with idling from the get-go. Perfect circle used to recommend a ring break-in procedure consisting of 10 full throttle accelerations from 30 MPH to 50 MPH to let compression and acceleration cylinder pressure force the compression rings tight against the cylinder walls to scuff them into a running fit with the crosshatch in the cylinders. Jerry
"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt! There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway Love your enemies and drive 'em nuts!
I'm questioning this because I have never heard of a special cam break in procedure,I have changed a lot of cams as a mechanic,flat tappet style,roller style,overhead cam,we used a special cam lube and broke the engine in I described earlier. I just wanted to make sure I wasn't going to have cylinder glazing problems . I am in the middle of doing a complete 261 rebuild out of a 1962 gmc 920 and want to get things right.i have read a lot of the posts here and there are a lot things I have picked up to help me out as I get further into this. It's just an old engine,this should be easy!! Ha
I recently rebuilt a stock 350 Chevy complete with New Cam and lifters. Run in only required using either oil with zinc or an oil additive with zinc. I've been building engines and messing with cars for 50 years and until zinc was removed from motor oil I've had no problems with engine run in. My procedure has been 0 to 35 back to 0 briskly 4 or5 times. EFI engines have learning computers they adjust to your driving habits so run them in by driving them normally for about 2000 miles change the oil to your favorite brand .and get after it. On all new engines rebuilt overhauled or patched ie. cam and lifters use zinc additive or motor oil with zinc and avoid overheating and extreme duty for 2 to 3 thousand miles. I Also believe that zinc is helpful in seating piston rings. Zinc was probably removed from oil by the EPA. Stupid EPA.
The zinc along with other additives was removed for emissions from a request from the auto makers. The catalytic converters were getting fouled due to the oil formulas, so they asked to remove them since the new engines no longer needed the protection anyway. It wasn't long after that the flat tappet cam makers started seeing problems with flat lobes and worn lifters.
We used stock single valve springs to do the run-in on every race cam we installed, to keep the pressure of the triple spring setup off the new cam. After a 20-30 minute run-in on the dyno with the stock springs, we would pull the heads and install the heavy pressure springs. Of course, those engines were producing 700+ HP and turning 7K+ RPM. They were totally worn out in less than 1,000 miles around a 1/2 mile asphalt oval. Jerry
"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt! There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway Love your enemies and drive 'em nuts!
The zinc along with other additives was removed for emissions from a request from the auto makers. The catalytic converters were getting fouled due to the oil formulas, so they asked to remove them since the new engines no longer needed the protection anyway. It wasn't long after that the flat tappet cam makers started seeing problems with flat lobes and worn lifters.
If you have a high HP whumpa-wumpa motor then yes, you might need the added zinc (but at that point you should have roller cams, not flat tappets.. rollers see little benefit from added zinc)... but stock or warmed over motors... no.
The oil we use today has no more or less zinc than the original formula's from the 1940's and 1950's. The use of zinc spiked in the 70's as it was a cheap way to prevent the oil from oxidizing. zinc was never added to reduce wear, just to stop the oil from breaking down. To much zinc will eat the metal (via acid etching).
You are correct that the zinc exhaust gases might foul the O2 sensor or catalytic converter... but so can running rich (soot) excessive oil consumption and a host of other things.
Cam manufacturers blame the zinc for a period of time when cams were not lasting... I don't buy it. There never was a huge issue of cams being wiped that can be directly blamed on API certified oil.
