68gts340
Well-Known Member
ok here is a few things we learned 40 years ago about cam lobes failing. first of all with a flat tappet cam ,the lifter has to spin freely in the lifter bore. if the lifter cant spin the lobe fails,
second is a quailty control problem, the cam lobes have a very slight angle ground into them, this angle causes two things to happen, one is it creates a pre load to the cam shaft front to rear of the block, this is why flat tappet cams do not need a cam button or bearing to keep it from walking.
this angle is also the driving force that causes the lifter to spin, the spinning of the lifter is what cools and lubes the friction surface of the lobe and lifter.... the lifter will over heat as well as the lobe when the lifter fails to spin.....on a new cam the surface has not work hardened , it is still soft on the surface .. the breakin period is to actually harden the lobes .
we found several lifters that were not to perferct size, and were " stiff " in their bores , i found that a small ball hone was a good quick fix for a poor fitting lifter, we have also found some lifter bores also a little to small. again the ball hone.
we also found some people using the cam lube on the sides of the lifters, not a good idea. use motor oil. the lube is for the lobes and lifter bottoms. .
as you install the lifters twist them in to the bores so that you can feel any interferance, I actually spin every one just before it bottoms .if you cant spin it with your fingers ,you will lose that lobe.
many years ago we were plagued with cam failures , from many manuf. the biggest reason for failure was the angle on the lobes...to flat and the lifter wont spin. .
the second biggest reason was cheap castings. imported !!! .. big suprise !!
I am sure there are more reasons, but this is what we found many years ago...and only one cam grinder at the time stood behind his cams.. it was CRANE CAMS..... they also were the ones I worked with to solve many of the problems we had at the time,,,,to this day i still run crane cams...and havent lost a lobe in over 30 years.
well thats what we learned way back then , do your part installing them , and buy from somebody who stands behind their stuff, ....for what its worth
Ron...
p.s roller cams are a different story
second is a quailty control problem, the cam lobes have a very slight angle ground into them, this angle causes two things to happen, one is it creates a pre load to the cam shaft front to rear of the block, this is why flat tappet cams do not need a cam button or bearing to keep it from walking.
this angle is also the driving force that causes the lifter to spin, the spinning of the lifter is what cools and lubes the friction surface of the lobe and lifter.... the lifter will over heat as well as the lobe when the lifter fails to spin.....on a new cam the surface has not work hardened , it is still soft on the surface .. the breakin period is to actually harden the lobes .
we found several lifters that were not to perferct size, and were " stiff " in their bores , i found that a small ball hone was a good quick fix for a poor fitting lifter, we have also found some lifter bores also a little to small. again the ball hone.
we also found some people using the cam lube on the sides of the lifters, not a good idea. use motor oil. the lube is for the lobes and lifter bottoms. .
as you install the lifters twist them in to the bores so that you can feel any interferance, I actually spin every one just before it bottoms .if you cant spin it with your fingers ,you will lose that lobe.
many years ago we were plagued with cam failures , from many manuf. the biggest reason for failure was the angle on the lobes...to flat and the lifter wont spin. .
the second biggest reason was cheap castings. imported !!! .. big suprise !!
I am sure there are more reasons, but this is what we found many years ago...and only one cam grinder at the time stood behind his cams.. it was CRANE CAMS..... they also were the ones I worked with to solve many of the problems we had at the time,,,,to this day i still run crane cams...and havent lost a lobe in over 30 years.
well thats what we learned way back then , do your part installing them , and buy from somebody who stands behind their stuff, ....for what its worth
Ron...
p.s roller cams are a different story
