DeTomaso Mailing List: May 98, Message #46

The stock (non-Boss/HO) valves are made from two pieces and
use loose fitting multi-groove keepers to promote valve rotation.
Their are two primary failure modes.  The first is the valve can slip 
out of the keepers.  The other is the head can be pulled off the stem.
The valves might be okay with stock springs but add a high lift cam
with stiff springs and bad things can happen.  I grenaded my first
351C that way.  I was given a virgin standard bore 351C and did a
typical rings and bearings rebuild, adding a 0.550" lift cam.  The stiffer
springs yanked the head off the stock exhaust valve.  The valve head
smacked the piston which shattered and the rod ventilated my block.
The quench head was ruined but the keepers held firmly onto the stem.
I've talked with more than one Cleveland owner that had this happen.
If you ever open up the engine, pitch the valves and replace them with
quality one-piece, single groove, stainless parts.  Are you listening
Asa Jay?

Later,
Dan Jones

>>> "Charlie McCall" <Charlie.Mccall@HaworthInc.com> 05/01 5:27 am >>>
While I'm thinking about it, could someone educate me a little bit - what
causes a valve to drop in the first place? Dave D did it because he used
a cheaper part that wasn't up to the task, if I remember correctly. My
motor is a relatively stock one with 37 or 38K miles on it, so it hasn't
been driven a zillion miles and is just worn out. Got to wondering, because
even if I didn't do this I'd wonder about doing it in the future, since
others have done so  in the past...

Thanks

Charlie McCall
1972 Pre-l
#3847