Terrible Tom <SilverEightynine@earthlink.net> wrote:
: SEMIHEMI01@aol.com wrote:
:> Tom,
:> Sounds like a collapsed valve lifter to me. It may eventually pump
:> back up. An oil change may help this problem.
[...]
: I would hope what you said is right. But I have solid lifters?
: Not rollers? This is an old premag V6. I know the push rods are
: hollow - is it possible that one is clogged and isnt getting enough oil
: through?
Tom,
What you are probably referring to is a "flat tappet" lifter. Granted,
I don't know a whole lot about the premag engines, but I am about 99.9% sure
you have hydraulic lifters, and not solid lifters. One term refers to the
way the lifter contacts the cam, and the other term refers to the internal
design of the lifter.
There are essentially two "internal types" of lifters:
Hydraulic: Fills with engine oil and has a spring inside; this
allows them to be preloaded and they will more or less
automatically compensate for valvetrain variables.
The vast majority of engines use this type of lifter.
Solid: This is basically a solid steel cylinder, which does not
fill with oil, and therefore does not compensate for
valvetrain variables. As such, a valvetrain using solid
lifters will require occasional adjustments to keep
everything running at its best. These type of lifters
are usually found only on race engines where the constant
tune-up hassle is less important than every last bit of
power.
There are essentially two "body styles" of lifters"
Flat tappet: The bottom of the lifter (which rides on the cam) is flat.
(Actually, they are usually *slightly* rounded.) Up until
recently, just about all engines used this type of lifter,
but in late model engines, rollers seem to be the lifter of
choice.
Roller: There is a roller on the bottom of the lifter which rides
on the cam. The advantage of the roller is less friction,
and even more important, a faster "ramp-up" ability. A
roller cam can be ground very steep to give a high rate of
lift because you don't have to worry about the edge of a
flat tappet roller digging into the side of the cam, which
would have pretty much the same effect as jamming a stick
into a bicycle's spokes. ;-)
You can have hydraulic flat tappet lifters, solid flat tappet lifters,
hydraulic roller lifters, and solid roller lifters.
So basically what I am saying is that "solid lifter" and "roller lifter"
are not opposites - they just describe a different part of the lifter.
I am almost positive what you have are hydralic flat tappet lifters.
If a hydraulic lifter "pumps down", essentially what it is doing is to
eliminate the preload and create "slack" between the lifter, pushrod and
rocker. When the lifter is all the way down, the pushrod may be losing
contact with the lifter. The sound you are hearing would be the lifter coming
up again, and slamming into the pushrod (or more likely, if the pushrod is
riding on the lifter at all times, the sound would be the pushrod hitting the
rocker) You *might* be able to determine which lifter is pumped down by
removing both valve covers, then watch and wiggle the pushrods as you turn the
engine over by hand. If one of them gets really loose when the pushrod bottoms
out, that is probably the culprit. They will still have a spring in them though,
so you may need to push down on the pushrod as well (maybe by pushing down on
the rocker) - it may be that even though it is not pumped up, the spring inside
the lifter might be holding enough tension on the pushrod so that just wiggling
them won't readily show which one is to blame.
If you don't want to bother taking off both valve covers, you may be able
to listen carefully at both valve covers with the engine running to see which
side of the motor is creating the noise. A mechanic's stethiscope would be
useful for this, or you can also try holding a long screwdriver against your
ear and touching it to the valve cover, or hold a rubber hose up to your ear
and touch it to the valve cover.
You would need to pull the intake manifold and remove the rocker and
pushrod order to get to the lifter so this may not be as useful as it
seems, but it would at least help to confirm wether or not it is indeed
a pumped down lifter. If it does come to the point where it doesn't eventually
pump back up by itself and you find the culprit lifter, you can try to
dissasemble it (push down on the pushrod cup and remove the retainer, then the
pushrod cup, a spring and maybe a few more parts will come out) then clean
everything well with carb cleaner before reassembling it. Make sure you keep
all of the lifters and pushrods together and install everything exactly back
where it came from. Pushrods, rockers and lifters tend to wear together, and
especially important with a flat tappet lifter, the cam and lifters wear
together, so you want to keep them together.
As far as re-installing the lifters goes (if you dissasemble and clean
them), I have heard some sources say to soak them in motor oil to let them
fill with oil, and other sources have said not to do this - to let them
pump up on their own. I have no idea which way is better, maybe someone
more knowledgeable than myself can comment on the pros and cons of both
methods. Whichever way you do it, be sure to at least coat everything
(lifter bores, lifters, pushrods) with some oil to provide a bit of initial
pre-startup protection).
: I'm going back out in a few mins to restart the engine and let it run a
: little longer. Im keeping my fingers crossed. if the engine is bad -
: then I can say for almost certain - I wont be able to make the BBQ this
: July :-(
Good luck!!! Everyone here at DML HQ is pulling for ya! :-)
---Jon-
.---- Jon Steiger ------ jon@dakota-truck.net or jon@jonsteiger.com ------. | I'm the: AOPA, DoD, EAA, NMA, NRA, SPA, USUA. Rec & UL Pilot - SEL | | 70 Cuda, 90 Dak 'vert, 92 Ram 4x4, 96 Dak, 96 Intruder 1400, 96 FireFly | `------------------------------------------ http://www.jonsteiger.com ----'
This archive was generated by hypermail 2b29 : Fri Feb 06 2004 - 11:46:14 EST