I'm trying to figure out why I keep having cam issues. Both cams(2) have gone flat on #6 cyl. Ex. Don't know why, ANY suggestions would be greatly appreciated. Engine a 312 w/ported ECZ-g heads,Mummert spec'ed cam

I hate to ask this but you  ARE using a new set of lifters with each new cam right?! If so I would proceed as follows; since it is the #6 cylinder I would pay very careful attention to valve spring installed height and seat pressure on that cylinder.Be sure that your springs have a minimum of .060" travel remaining before coil bind at full lift.Also be very sure of valve travel-I E how far the valve can move before the upper retainer hits the guide\seal.This also should be around .060"min. at full lift.Lack of clearance in either place will take the cam out right fast! I assume you are using plenty of cam and lifter assembly lube and paying careful attention to valve clearance.It sure sounds to me like you are bottoming a valve or spring.It is critical to check each valve for spring and valve travel during head assembly.

Also check that guide to see if it is too tight. You should be able to wiggle the valve in it..It might be tighter than the others and seeing it is an ex valve it bears checking out..  Did the cam lobe go, the lifter,  or both?  Also check that lifter bore.  The lifter should spin easily with your fingers and not have any tight spots or binding with up and down movement.. Losing cams really sucks. Finally, Comp and others offer a nitriding process which puts additional hardness on the surface of the cam.. Trend tool steel lifters seem to be very durable.. At this point you do not want to do it a 3rd time

What does the lifter look like?  Is it spinning in the bore? What lifters are you using?

   God Bless.   Tim                           http://yblockguy.com/

350ci Y-Block FED "Elwood", 301ci Y-Block Unibody LSR "Jake", 312ci Y-Block '58 F-100, 338ci Y-Block powered Model A Tudor

tim@yblockguy.com  Visalia, California    Just west of the Sequoias

Thanks for the reply, I'll be pulling the engine out next month to investigate. Don't know if it's cam or lifters. Yes both new,

I suspect a guide that gets too tight when the motor gets warm.   I had to replace a few valves after loosing a motor and bending a few valves once, and the new valves were just slightly thicker stems.   They seemed to go in fine, feel good, but the same lobes were going bad.   Had those guides corrected, and the problem seemed to be solved.   Also, always make sure the lifters spin freely when installing them.   You can watch to see if the pushrods turn when you start the motor.

I am a big fan of having everything perfect, including a known working carb, before start up.   The engine needs to go to 2000 rpm instantly on start up and stay there for 20-30 minutes.   The cam is only oiled by the oil slinging off the rods, and you must have enough rpm to get the oil pressure high enough.  

I like to keep the timing advanced a bunch to keep the headers from getting so hot.

Pat Fleischman

Here’s the link to a list of items that can contribute to cam/lifter failure.  Any one of these or a combination of them can cause problems.  There’s a known problem with offshore lifters so try to rule that one out also.  If you purchased the lifters from John Mummert then you should be good on those assuming the lifters were also replaced with the second camshaft.
http://www.eatonbalancing.com/blog/2012/11/06/camshaft-and-lifter-failure-causes-2/

Lorena, Texas (South of Waco)

I have talked to  2 cam grinders in bc, they both say,most of the flat tapet cam failures  are the source of the blank(china).1 of thes companies  that do a lot of cummins cams(dodge) gets his blank cast in the us, to his spec. the 2nd co is verry sure the regrind is on a older cam of knowen quality. this is hearsay and i only have this info from the shops.Tho i have never had a failure with a regound cam,this includes maney years working for cat dealer with 3306 and 3208 engines with flat tappet cams. also as hobey of rebuilding gas engins,mostly ford ys fes,as well as289/302a.

Both cams and lifters were new from Mummert.  With the v/covers off engine warm and running, lash set to .019 on in &ex, will the pushrods spin with the lifters? Will this confirm that the lifter is spinning? I will mark the pushrods #'s 5,6,7,8 to verify.

In most instances the pushrod will be turning if the lifter is turning but that’s not true 100% of the time.  If there is some friction going on at the cup end of the pushrod, then the lifter can still be potentially turning while the pushrod is not.

Lorena, Texas (South of Waco)