Cam break-in

[David Bodily]

I have read a lot about the danger of not doing a proper break-in of the cam on a new rebuild. I have also read that if you have trouble getting the engine started after a re-build that the assembly lube can be wiped off the lobes and early failure can occur. my question to all you cam experts out there is:
What happens during cam break-in. Is there a physical change to the lobes which hardens them? Also after the car sets for a period is there a danger of cam failure if the engine is turned over alot trying to start? Thanks I am just wondering how much it worry about. David

[Clem Z.]

Re: Cam break-in

it is just a "mating in" of the lifter to the cam lobe and once this is done there is no farther problems. this why if you remove any lifters you must put them back on the same cam lobe.

[Joe L.]

Re: Cam break-in

David-----

If you use an hydraulic roller cam, you avoid all of these problems.

[David Bodily]

Re: Cam break-in

Thanks for the info. It has removed some of the fog and flim flam I have read about this. David

[Duke W.]

Re: Cam break-in

How did GM break in the cam - test fired it for about 30 seconds at the engine plant, then when it was installed in the car, it was fired up went through the roll test and driven out to the parking lot. After that it was started to move it onto trucks or rail cars, then moved around the lot by the dealer.

These "short trips" are absolutely the worst thing you can do to an engine, but with the modest OE valvesprings and lobe acceleration characteristics 99.999 percent of the cams made it through okay.

The normal cam breakin procedure - fire the engine and get it to 2000 for 20 minutes is necessary with a racing cam. It is certainly a good idea for a rebuilt engine, but is not absolutely necessary.

To insure that the engine fires quickly fill the carb bowls through the vents with a syringe until fuel just begins to drip out the venturi nozzles. Set the engine at the proper initial timing point or about 10 TDC (NOT TDC) and rotate the dist. until the points just begin to open, then back it off a hair. This will get your initial within a couple of degrees of spec. Do the normal cold start procedure to add a pump shot and set the choke. Wait about 30 seconds to a minute to let some of the liquid fuel evaporate, then crank it. It should fire right up.

Duke