chevy 350 cam question (moves in and out while turning)

Recently my distributor gear stripped. I pulled the motor a part to
replace cam, and after replacing the cam I turned the new one by hand
with a couple bolts in the end of it, and while turning I noticed the
cam walks out about a 1/8 inch like it has a lobe at the back of it.
this makes no sense to me and would explain the stripped distributor
gear. Is this normal? Is this what makes the lifter rotate? Anyone
heard of this? thanks for your replys.

Look very closely at the distributor shaft for trueness. The cam may be
getting a shove from a bent shaft...


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Ok, thanks for the replys. I didn't have the distributor in yet.. I
just removed the pushrods and lifters and the cam turned fine, I put
all the lifters back in and same problem, just not as bad....until a
couple turns then one lifter stays up and cam turns smooth again.
Everything seems ok no burrs etc when I put my finger in the hole.
The lifter is a little snug, but I can move it in and out with my
finger tips. I think I will just put it all back together and see how
it is with oil flowing through everything. I will make sure that
pushrod is turning when I start it up.

wrote:

> wrote

> Ok, thanks for the replys. I didn't have the distributor in yet.. I
> just removed the pushrods and lifters and the cam turned fine, I put
> all the lifters back in and same problem, just not as bad....until a
> couple turns then one lifter stays up and cam turns smooth again.

I bet it's not a "roller" camshaft, right?
The camshaft lobes are not flat (they're not supposed to be).
The faces of the lifters aren't flat (they aren't supposed to be either).

The lobes are ground on a bit of an angle, and the lifter faces are slightly
convex (they bulge out). It's designed that way so that as the camshaft turns,
the lobe rides against the lifter face off-center, making the lifter rotate in
the bore, presenting a new surface for the next "lift". This evens out the
wear across the lifter face, and greatly reduces the friction on both parts.

When you turn it by hand, the lobes/lifters aren't sliding like they will when
everything's fully lubed, so the "contact point" will tend to follow the rotation
of the lifter, in or out depending on which way you're turning the cam.

Here's another description, using highly technical terms:

It's the same as using a finger to manually spin a disk on one of those
pre-historic devices called "record players". If you move your finger straight
across the record, it will turn a bit, and your finger will slide off the edge.
If your finger encounters a blob of jam that fell off your toast onto the record,
the increased friction will tend to glue your finger to the record, forcing your
finger (lobe), and arm (camshaft) to follow the jam blob (contact point) on the
record (lifter face) as it rotates towards or away from you.
Hmmmm... I'm feeling a bit hungry for some reason.

Nate Nagel wrote:
>
> When reinstalling the distributor, make sure the engine is at #1 TDC on
> the compression stroke, then turn the rotor so it is pointing at #1 plug
> wire when it's dropped all the way into the engine. The gear is
> helically cut so the rotor will rotate as you drop the dist. down, this
> is normal (and I assume why your cam is trying to walk) once you have
> everything in place unless you got real lucky the dist. will probably
> not seat all the way because the oil pump drive will not be lined up,
> just leave it in there, use your remote starter switch to bump the
> engine over while keeping light pressure down on the dist. with your
> hand, it should drop into place before the engine makes a full
> revolution. check for oil pressure before allowing the engine to start.
>
> good luck,
>
> nate
>

Two comments:
take an old distributor and pop the gear off, and use a 1/2" drill and
prime the engine first. Your bearings will thank you. And if you do
this on an engine stand without the oil pressure sending unit hooked up
at the back of the intake, you can spray 10W30 10 feet in the air.
*(you can also buy a tool to do this.)* Do it until oil starts coming
out the pushrods.

Use a long screwdriver and turn the oil pump "tang" to line up with how
you want it to be once you drop the distributor in. If it's all lined
up right, it will all "drop right in" - no bumping the starter necessary.

This is one of those things that I used to be very green at, but have
gotten good at because of the race car. This time we managed to be at 8
degrees of timing and the motor started immediately - no cranking. Not
bad, considering we were aiming for 10 degrees.

Ray

gopher wrote:
> ray wrote:
> > Nate Nagel wrote:
> >ray i have a question, I pulled a dist. from an olds 350 and marked where rotor pointed. dropping it back in i lined it all back up. now i have to turn the housing a lot farther than i think it should be to get it to fire. could i be one tooth off? Thanks Keith.

"gopher" > wrote in message
ups.com...
>
> gopher wrote:
>> ray wrote:
>> > Nate Nagel wrote:
>> >ray i have a question, I pulled a dist. from an olds 350 and marked
>> >where rotor pointed. dropping it back in i lined it all back up. now i
>> >have to turn the housing a lot farther than i think it should be to get
>> >it to fire. could i be one tooth off? Thanks Keith.
>
Yes. Often when you drop it right back in where the marks line up, it
fails to mesh with the oil pump until it rotates a few degrees, at which
time it falls the remainder of the way down. This can put you off a tooth.
HTH, s

sdlomi2 wrote:
> "gopher" > wrote in message
> ups.com...
>> gopher wrote:
>>> ray wrote:
>>>> Nate Nagel wrote:
>>>> ray i have a question, I pulled a dist. from an olds 350 and marked
>>>> where rotor pointed. dropping it back in i lined it all back up. now i
>>>> have to turn the housing a lot farther than i think it should be to get
>>>> it to fire. could i be one tooth off? Thanks Keith.
> Yes. Often when you drop it right back in where the marks line up, it
> fails to mesh with the oil pump until it rotates a few degrees, at which
> time it falls the remainder of the way down. This can put you off a tooth.
> HTH, s
>
>

which isn't the end of the world, because it'll still run. There's
three problems with doing it this way... your plug wires may not reach
anymore, adjusting the timing is a pain because the vacuum advance hits
things, and the next owner will be cursing your name because what should
be plug #1 isn't.

But yeah, the best thing to do is pull it back out, rotate the oil pump
drive back a bit and drop the distributor back in.

Ray