After I break in my cam do I need to re adjust the rockers? A guy at work claims that during cam break in you can lose up to .030 of the cam lobe. I don't really believe him but I did a search on this site for rocker adjustment and none of the threads seem to mention this.

My real concern is weather or not I have to re-adjust the rockers on a flat tappet cam after it is broken in. Is this a standard proceedure or not?

 

No, not unless they are making noise. Loose .030" on break in? Not unless you did something wrong.

 

I agree, BUT it also depends on how much preload you put on them when you adjust them the first time.

NON roller cams WILL wear...that's what break in is for. To keep oil to the cam and lifters to help with the extra friction / heat that happens as two new metal surfaces get "friendly" with each other.

I've always had good luck with a FULL Turn of pre load before break in on a flat tappet hyraulic.


YMMV

 

I agree, shouldn't be necessary. New factory motors don't require it; why should a properly executed rebuild made out of essentially identical parts be any different?

In my experience, the real number is more like .003" of cam lobe and lifter base wear, not .030". Somebody got vicitmized by the dancing decimal point. .003" is about 1/20th of a turn of the rocker nut.

I'd leave them alone if you're sure you got them set right during assembly, unless there's some symptom of needing attention; noise, uneven running, etc.

 

That's funny. I've never heard it said like that. Thanks for the laugh.

 

RB makes a good point. But one thing I see alot on new / rebuilt engines, or even engines with new cam / lifters...

The lash seems to be adjusted on the loose side by alot of people. I think it comes from the whole "spin the pushrod until it's tight" thing...that doesn't really work with new parts in my opinion, and when worn pushrods get "polished" on the ends, it doesn't make it as accurate, again, MY opinion, as setting zero lash while moving the pushrod vertically back and forth against the lifter / rocker.

 

On a hydraulic lifter, I like to watch the plunger. When it depresses slightly & the pushrod is snug, i know it's right.

 

Thanx for all the input. I feel a little better about it now. I was sure that it was bull crap that .030 inch would wear off during break in.