tips on engine break in
Updated: Jun 15, 2022
so you've just rebuilt your engine and you've got it stabbed in your car and you're getting ready to fire it? here's my standard procedure/routine i've developed over the years for engine break in.
first things first, if you're going to run an exotic intake set up such as 6-2s or 4-2s, etc... then its highly suggested that you put a known to be good and jetted right four barrel carb and intake on the engine to break it in, that way you arnt risking flattening your cam or running it lean or excessively rich, or idling it excessively while you screw around with linkage and all the other adjustments.
start by priming the oil pump. if you don't have the correct tool, you can use a screwdriver with the plastic broke off the handle or an air chisel bit chalked up in a drill to spin the shaft through the distributor hole. spin it until oil drips freely from the rocker assemblies on each side. if youre not getting oil, then youve got a serious problem. oil gallery plugs could be left out, plugs could be pushed in too far blocking the tiny passages (common when guys run screw in plugs, which BTW are not necessary on these engines.) and i've even seen rare instances where the oil passage in the head gasket was never stamped out. cam bearing may be installed wrong. otherwise, very little oil goes to the top end on these engines. you can idle them no problem with the valve covers off... so mild oil dripping while you spin the pump is what you're looking for. now turn the engine over to top dead center, if the engine was at top dead center prior to stabbing, it more than likely isnt now if you've turned the engine to install converter bolts. you can rotate the engine until the intake valve closes and then continue to turn the engine clockwise until the timing mark lines up. thats TDC. if valve covers are installed, you can look through the intake runner with the intake off, just the same. now stab the distributor. rotor should point at 8 o'clock to number 1 on the cap, if you are standing in front of the engine looking back. be 100 percent sure the distributor is seated all the way down in the oil pump!!!!! this is a huge common mistake people make. if the O ring has no lubrication, the drag makes people think its down all the way when it isnt! now static time it.
if you've never heard the phrase before, static timing is basically giving you a starting point for initial timing so you arnt screwing around cranking the car excessively and it gets you in the ballpark of the car being timing properly, so you can focus your attention on oil pressure and leaks, as well as other distractions. to static time it, while the rotor is at #1 as stated above, with your coil hooked up, ignition to positive, and negative to points. take the coil wire off the cap and lay it next to a ground like an intake bolt.... rotate the distributor counter clockwise. as #1 on the cap passes the rotor, a spark will jump from the wire to the ground, snug your dist hold down clamp snug at this point and hook the coil back up.
the next step is to insure there's a MINIMUM of four gallons of coolant in the system. i always drill a tiny hole in the thermostat to bleed any air pockets out of the system. i typically add a gallon at a time and walk away and do something else. if theres an air pocket in the system you can cause serious mechanical damage during cam break in, without mentioning all it takes is a minute and a half to melt a rear main seal which is a big disaster. go over all hose clamps with a quarter inch ratchet. not just a nut driver. if you have a pressure tester, thats always a good idea. i always run a 160 thermostat and use panty hose in the upper radiator hose to act as a filter to catch any debri left over from blasting and tanking. read more about that in the "overheating issue tips" blog article i already did.
purple wire goes to S terminal on starter. yellow goes to R terminal. if you are running an electronic conversion, then the r terminal doesnt get used at the coill gets a full twelve volts all the time. if you are running points with a mini starter, you need a special pig tail that we sell. as for kickdown and variable pitch wiring instructions and diagram, please check the tech info section on the website. do not run power to the VP, kickdown, and electric choke from the coil. if you are running a tach, it goes to negative side of coil.
as for break in oil, i don't use break in oil. i'm not saying that you can't, or shouldn't, but i dont these days. ive had excellent luck just running 10w30 valvoline VR1 as a break in oil (VR1 has proper amount of zinc already). personally, i stay away from heavy weight oils on these engines. especially during break in. in my opinion, heavy 50 weight oils can actually keep the rings from seating. heavier oil doesnt mean better protection. the factory didn't use break in oils. you don't have to either... i don't advise using synthetic oil on vintage engines, but if you insist, id wait until after break in, as ive heard from other fellow builders that synthetics can also keep the rings from seating efficiently.
take note that you cannot run these engines with even a small amount of bad gas, even diluted with fresh gas. if you are unsure if theres bad gas in the tank, it's not worth the risk. even just a gallon of bad gas mixed with a full tank can cause the intake valve to lock up in the valve resulting in bent valves, bent pushrods, broken rockers, etc. if the exhaust valves lock up (which is extremely common.) then thats an indication that the guide clearances are too tight! intake valves need .002- .0025 and exhaust needs .003 to .0035. valve stems that are available typically have .0005 to .001 of stem taper. so tight figures should match the big end. do not use bronze guides with stock rockers. they will wipe out in 500 miles, with the exception of use of roller rockers.
once you fire the engine (be sure you have some kind of oil pressure guage installed that you can monitor.) keep the rpms between 2000 and 2500 for cam break in. oil pressure should read between 40-45 on 57 to 66 and 35-40 on the 322/264. 20-25 at idle. engine must be ran at that rpm range, for 20-30 minutes to supply cam lobes with enough oil to keep it cool during the mating break in process, which involves high friction and excessive heat. you do not need to run the engine for 20 minutes straight. in fact i advise against it. for the first fine, i typically only run the engine for a handful of minutes and it reaches opperating temp, static timed. while i look over the engine for anything overlooked. keep an eye on coolant temp, oil pressure, fuel leaks or flooding, as well as obviously coolant and oil leaks. i also typically dont want to get it too hot on the first fire for the sake of engine paint longevity. less likely to get wrinkling if you don't shock it with excessive heat if its not cured 100 percent.
i'll then let the engine cool. go over exhaust manifold bolts again. gaskets shrink, so its not uncommon to have to go over everything again on the engine. head gaskets do not need to be re torqued. the second time you run it, now have your dial back timing light ready and base your initial on your total while you finish cam break in. stock and mild cams require 30 degrees total with the vacuum advance disconnected. now that the cam is broken in. engine sound quiet and car is looked over, nows the time to drive it. its imperative you dont let the engine idle excessively for the first couple hundred miles. if its during the summer, its important to not put yourself in a position where you will get stuck in a traffic jam, idling excessively. as it is, fresh street engines tend to run much hotter when they are fresh than after they are broken in. how quickly its broken in is contingent upon how its driven and how often its driven. when you're on the freeway, contantly vary your speed, changing rpm ranges. how the engine is broken in, drastically impacts the rest of the life of the engine. whenever you're in 25pmh zones or residential areas, put it in low gear to keep the rpms up and the engine under load. the engine being under load is what seats the rings quickly. edelbrock carbs are typically safe to run right out the box with mild and stock cams but will need to be fattened up if gone significantly bigger or you live in really low elevation. good idea to take the car to someone with a gas analyzer. after cam break in and a test drive. change the oil. refill it with your conventional zddp/phospherous zinc oil and change it again after 200 to 500 miles. after that, it's just 3-5k mile oil changes for the rest of its life. most people dont even drive these cars that much in a year, so once a year oil changes on a car that hardly gets driven is just fine.