Cam shaft break in

Levi

Well-known member
Jul 27, 2004
512
0
Cheyenne, WY
I pulled up an old thread of mine and I thought this info deserved to be in the tech section. Good info from PhD_Polymath (thanks for sharing!)

1.) New cams require new lifters (at least). New pushrods would also be nice, but I haven't seen huge problems with reusing pushrods, as long as they are not warped. Roll the rods on a flat surface to check them for bends. Also, it is best to put the pushrods back with the same lifter and rocker arm, as they wear together. This wear pattern is probably not the same as the lifter and cam lobe, but unique nonetheless.

2.) For the love of all that is holy, make sure a new cam and lifters are broken in properly. Absolutely smother the cam and lifters in the most tenacious cam lube money can buy during assembly. Gibbs racing makes a superb assembly lube for this. It is the same lube Mark at D&D provides with his camshafts (he is the original "performance" camshaft supplier for Rover V8s in the U.S.A., and takes Buick Crower cams and modifies them to work with Rover timing sets, etc.).

3.) Add a bottle of ZDDP camshaft break-in additive to your oil for the break in (and if you are like me, every oil change). ZDDP is zinc dialkyl dithiophosphate. This compound is an anti-wear additive that provides a "cushion" at the interface of metal parts like the lifter face and cam lobe contact point and prevents your engine destroying itself in spectacular fashion immediately upon start up with a new cam. Note: Rotella T used to have a sufficient amount of ZDDP, but like most other oils, has lowered the amount to comply with emissions regulations. Some fancy racing oils have good amounts of ZDDP, but I would pick something like Brad Penn 30W break-in oil (or something equivalent) and add the ZDDP additive to that.

4.) Do not let the engine crank and crank before starting the first time with a new cam. This also means do not turn the engine more than necessary during assembly, as you will just be wiping off the break-in lube from the cam with the lifters. This will result in metal-on-metal wear and is akin to throwing money in the toilet.

5.) Upon starting the engine the first time, IMMEDIATELY! bring the engine to around 2000 RPM. Slowly fluctuate the revs from 2000-3000 RPM, stopping for a few seconds at 250 RPM increments or so. Do this for no less than 30 minutes (some say 20 is okay, but why not just keep it going for 30, like so many experienced engine builders recommend?). Keep an eye on the temperature with an OBD2 scanner if possible and have someone else watch for leaks and top off coolant while you keep the RPMs up. The reason the engine has to be revved like this is because, in addition to the oiling of the cam and lifters from the oil galleries that supply the rockers from the shafts and the lifter bores, the cam also receives oil slung from the crankshaft. If the engine drops below 1500 RPMs during this initial break-in, a fair amount of oiling is being missed out on and the results can be a flattened lobe in that first 20-30 minutes. If for some reason, the engine has to be shut down due to temperature, leaks, etc., just shut it off and take care of the issue. Once restarted, pick up where you left off. Also, do not just tie the throttle at one high RPM. The RPMs must be varied in the 2000-3000 range during the break-in.

6.) Once the cam and lifters are broken-in, let the engine cool off and change the oil and filter. I always use non-synthetic oil and would certainly recommend sticking with dino oil. At least during the break-in you don't want to use synthetics. Be sure to throw in a bottle of ZDDP additive.

7.) After 500 miles, change the oil again. After this change, you can go to a standard 3000 mile oil change interval if you want. Keep using either an oil formulated with sufficient ZDDP or adding a bottle of ZDDP additive each time.

Notes: I know some people get away with not following these directions and have no problems. I consider them lucky. The cost of a new cam going south on you can mean a complete engine overhaul, as the metal from flattened cam lobes can ruin your bearings, along with crankshaft and connecting rod journals. Yes, you may get lucky and it all gets caught by the oil filter. Maybe you will not. For just a few more dollars, you can lower your risk for such a costly outcome. Also, I know oil is a source of great contention. My advise is to use non-synthetic with a ZDDP additive. For the break-in, if you do not do the rev thing, you are playing with fire. I don't personally know anyone who has gotten away with this. I have, however, seen many cases of 15 minute old engines destroyed by just letting them idle along upon starting. New engines are not bothered by this, as they have roller valve trains or overhead cams.

Good luck either way you go and I hope you have the engine sorted and back to being full of character soon!
 
Last edited:

PhD_Polymath

Well-known member
Feb 6, 2015
98
1
Slightly west of Boston
Thanks for the shout out. Camshaft break in is important. In my first experiences building engines, I had 3 cams go flat in a 2 year time span. It really stinks to have to rebuild everything right after finishing an engine because of east-to-avoid mistakes.