Tigers List Archive

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Mail From: "Arnie Sugar" <(email redacted)>

Oddly enough, I had the same power loss/rough engine thing just happen,
and it was the fuel filter. However, that was just a warmup for things
to come...
Last week I heard a loud top end knock, which upon removing the valve
cover turned out to be a bent pushrod and rocker arm askew on the valve.
Of course its on the #8 intake, the farthest one back, the only one that
can't be installed with the heads/motor in place? or are there any
tricks for this? Small comfort, I could get the bent rod out.
Any ideas on what would cause this, what to look for, how far to tear
down, etc? I'd like to know what caused it before just replacing the
pushrod, no? Should I pull the head off ? I inspected all the other
pushrods on that side, #7 intake was also bent, but the rocker was still
aligned. Details - it's a 289, with only 3000 miles on it, albeit
rebuilt around 15 years ago, with a Crane cam, hydraulic lifters, chrome
moly TRW pushrods, and it burns some oil (I always suspected the engine
didn't break-in properly - not sure if this could be related). I'm a
bit rusty, as I haven't opened up a V-8 in over a decade.
Arnie

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Mail From: (email redacted)

well if the valves floated it could cause that or if the lash was not
properly set. do a compression check on that cylinder. i doubt you could bend
a pushrod and not hurt something else. also if the cam/spring package was too
big, the spring pressure could over power and bend a pushrod. just a few
ideas.
later
chris

It's all stock, just ask me!

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Mail From: "Palmer, Robert L." <(email redacted)>

Arnie,

You need to use hardened pushrods if you use guideplates. Also, stock rocker
arms may not have enough clearance for your high lift cam. The third
possibility is there is not enough clearance for the springs. Many high
performance springs, especially the double or triple spring type, require
special machining of the spring seats. This list is in the order of
increasing probability.

Bob

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Mail From: Craig Wright <(email redacted)>

Early 260, and 289 (pre '68, I think.) used a ball and socket type
rocker arm and the arm was prevented from moving by narrow push rod
holes in the head. These holes act as sort of a guide plate. Later heads
had larger push rod holes and used what is called rail rocker arms to
prevent rotation of the rocker arm. These arms have small ridges on the
side of the rocker arm that comes in contact with the valve stem. These
ridges extend down the side of the valve stem .040" or so and prevent
the arm from twisting. A problem occurs if you mix up these two systems.
I had a 289 rebuilt years ago with that problem. It went about 3000
miles before a rocker arm became askew and bent a push rod.

Craig Wright



Arnie Sugar wrote:
>
> Oddly enough, I had the same power loss/rough engine thing just happen,
> and it was the fuel filter. However, that was just a warmup for things
> to come...
> Last week I heard a loud top end knock, which upon removing the valve
> cover turned out to be a bent pushrod and rocker arm askew on the valve.
> Of course its on the #8 intake, the farthest one back, the only one that
> can't be installed with the heads/motor in place? or are there any
> tricks for this? Small comfort, I could get the bent rod out.
> Any ideas on what would cause this, what to look for, how far to tear
> down, etc? I'd like to know what caused it before just replacing the
> pushrod, no? Should I pull the head off ? I inspected all the other
> pushrods on that side, #7 intake was also bent, but the rocker was still
> aligned. Details - it's a 289, with only 3000 miles on it, albeit
> rebuilt around 15 years ago, with a Crane cam, hydraulic lifters, chrome
> moly TRW pushrods, and it burns some oil (I always suspected the engine
> didn't break-in properly - not sure if this could be related). I'm a
> bit rusty, as I haven't opened up a V-8 in over a decade.
> Arnie

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Mail From: "Ronak, TP (Timothy)" <(email redacted)>

Arnie,
This sounds bad as pushrod failure usually does not happen unless there is
contact with the valve to piston or some other physical contact or bind. If
this contact did happen and you replace the pushrods it will likely miss due
to the new tweak that you have in the valves affected. If not you were very
lucky.
Couple of questions: Any spirited driving like some high RPM? Is it possible
that the Rocker bound on the rocker stud? Is it possible that the springs
coil bound? Is the cam solid or mechanical? What is the clearance between
the spring coils at max lift? Were they both Intake valves? Are there valve
reliefs milled into the pistons? Did you check valve to piston clearance? Do
you have guideplates and if so do they show any wear?

Best Regards,

Tim Ronak
Business Development Manager
Akzo Nobel Coatings
Off: (949) 305-5393
Fx: (949) 305-5394
Cell: (949) 439-4784
email: (email redacted)
VM: (800) 234-6747 ext. 2257#

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If you are not an intended recipient, please notify the sender then delete
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Mail From: Larry Paulick <(email redacted)>

Arnie, do you have screw in or pressed in rocker arm studs. If pressed
in, and high stress, it may pull the stud out far enough to loosen the
rocker arm, and the push rod comes out of its location.

This does not preclude further damage, but you may be lucky.

Larry

"Ronak, TP (Timothy)" wrote:
>
> Arnie,
> This sounds bad as pushrod failure usually does not happen unless there is
> contact with the valve to piston or some other physical contact or bind. If
> this contact did happen and you replace the pushrods it will likely miss due
> to the new tweak that you have in the valves affected. If not you were very
> lucky.
> Couple of questions: Any spirited driving like some high RPM? Is it possible
> that the Rocker bound on the rocker stud? Is it possible that the springs
> coil bound? Is the cam solid or mechanical? What is the clearance between
> the spring coils at max lift? Were they both Intake valves? Are there valve
> reliefs milled into the pistons? Did you check valve to piston clearance? Do
> you have guideplates and if so do they show any wear?
>
> Best Regards,
>
> Tim Ronak
> Business Development Manager
> Akzo Nobel Coatings
> Off: (949) 305-5393
> Fx: (949) 305-5394
> Cell: (949) 439-4784
> email: (email redacted)
> VM: (800) 234-6747 ext. 2257#
>
> This message, including attachments, is confidential and may be privileged.
> If you are not an intended recipient, please notify the sender then delete
> and destroy the original message and all copies. You should not copy,
> forward and/or disclose this message, in whole or in part, without
> permission of the sender.

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This read-only message was archived from a public mail list.
Mail From: "Arnie Sugar" <(email redacted)>

Thanks for all the input - here's a summary of theories, with my
comments and further questions for all you enginologists:

* Valve float due to high revving / missed shift / "spirited"
driving - I don't think this is the case, at least not just prior to
failure - I was just taking off, and going rather slow. Engine may have
been a tad cold.
* Rockers not adjusted - I suppose, but they never made any noise
prior to this
* Stock rocker arms may not have enough clearance for high lift
cam - would this have lasted 3000 miles? How do I check this?
* Springs too big / not enough clearance - would this have lasted
3000 miles? How do I check this?
* Pressed in rocker arm studs may have pulled out and loosened the
rocker arm. How do I check this? I think mine are threaded, but not
sure.
* Mismatched rockers & heads (e.g., big guide holes and no
rail-type rockers, or guideplates with non-hardened pushrods) - I don't
think this is the case, but don't have a sense for how tight the
clearance in the guide holes should be with flat faced (no rails)
rockers. My heads have a hole where the pushrod goes in, lots of play
up and down, and around 0.050" side to side. I'm not sure what a
guideplate looks like, or what the clearance in the head-hole should be.
This is likely the origin of the old expression "I need that like a I
need a hole in the head."

Tim, in specific response to your questions:

* Is it possible that the Rocker bound on the rocker stud? - I'm
not sure what to look for, but the rocker and stud looked OK.
* Is it possible that the springs coil bound? Also not sure what
you mean by this, or what to look for.
* Is the cam solid or mechanical? Are you referring to a roller
cam? I have hydraulic lifters. This is something I've always wondered
about: All cams are solid, no? The lifters are either solid, hydraulic,
or have rollers. When people refer to "roller cams" or "hydraulic cams"
does this refer to the cam profile to accept certain types of lifters?
Sorry if I seem like I just fell off the turnip truck...
* What is the clearance between the spring coils at max lift? Is
there a spec for this? Do I just rotate engine until valve is full open,
then measure clearance between the coils?
* Were they both Intake valves? Yes
* Are there valve reliefs milled into the pistons? Not sure,
rebuild was 15 years ago
* Did you check valve to piston clearance? I didn't build the
motor. How is this done, through the intake/exhaust port?
* Do you have guideplates and if so do they show any wear? No,
just the holes in the heads.

I think if a valve was hitting a piston, it would have happened earlier,
believe me, I've done more, uh... "spirited" driving in the past.

Thanks again to all, please let me know what you think some more - I'll
be tearing into it this weekend.
Arnie

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Mail From: Craig Wright <(email redacted)>

Hi Arnie,

It sounds like you have the correct head for non-rail type rocker arms.
I also bent a push rod that was caused by excessive clearance. I was
able to replace the pushrod with no other damage. A very positive check
would be to perform a leak down test on the affected cylinder. This will
show you if your valve touched the piston, because it will be bent and
not seal.

Craig Wright


Arnie Sugar wrote:
>
> Thanks for all the input - here's a summary of theories, with my
> comments and further questions for all you enginologists:
>
> * Valve float due to high revving / missed shift / "spirited"
> driving - I don't think this is the case, at least not just prior to
> failure - I was just taking off, and going rather slow. Engine may have
> been a tad cold.
> * Rockers not adjusted - I suppose, but they never made any noise
> prior to this
> * Stock rocker arms may not have enough clearance for high lift
> cam - would this have lasted 3000 miles? How do I check this?
> * Springs too big / not enough clearance - would this have lasted
> 3000 miles? How do I check this?
> * Pressed in rocker arm studs may have pulled out and loosened the
> rocker arm. How do I check this? I think mine are threaded, but not
> sure.
> * Mismatched rockers & heads (e.g., big guide holes and no
> rail-type rockers, or guideplates with non-hardened pushrods) - I don't
> think this is the case, but don't have a sense for how tight the
> clearance in the guide holes should be with flat faced (no rails)
> rockers. My heads have a hole where the pushrod goes in, lots of play
> up and down, and around 0.050" side to side. I'm not sure what a
> guideplate looks like, or what the clearance in the head-hole should be.
> This is likely the origin of the old expression "I need that like a I
> need a hole in the head."
>
> Tim, in specific response to your questions:
>
> * Is it possible that the Rocker bound on the rocker stud? - I'm
> not sure what to look for, but the rocker and stud looked OK.
> * Is it possible that the springs coil bound? Also not sure what
> you mean by this, or what to look for.
> * Is the cam solid or mechanical? Are you referring to a roller
> cam? I have hydraulic lifters. This is something I've always wondered
> about: All cams are solid, no? The lifters are either solid, hydraulic,
> or have rollers. When people refer to "roller cams" or "hydraulic cams"
> does this refer to the cam profile to accept certain types of lifters?
> Sorry if I seem like I just fell off the turnip truck...
> * What is the clearance between the spring coils at max lift? Is
> there a spec for this? Do I just rotate engine until valve is full open,
> then measure clearance between the coils?
> * Were they both Intake valves? Yes
> * Are there valve reliefs milled into the pistons? Not sure,
> rebuild was 15 years ago
> * Did you check valve to piston clearance? I didn't build the
> motor. How is this done, through the intake/exhaust port?
> * Do you have guideplates and if so do they show any wear? No,
> just the holes in the heads.
>
> I think if a valve was hitting a piston, it would have happened earlier,
> believe me, I've done more, uh... "spirited" driving in the past.
>
> Thanks again to all, please let me know what you think some more - I'll
> be tearing into it this weekend.
> Arnie

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Mail From: "Doug & Rett Leithauser" <(email redacted)>

Arnie,
I recently had my heads apart. I have a 1964 built 260 with non rail type
rocker arms.
On my cylinder heads the hole that the pushrod passes through is NOT round,
but is a machined hole that is very flat on the sides and rounded on the
ends, making an oval. I did not measure the clearance between the pushrod &
the head, but i'd guess it to be near 0.020", I'm pretty sure it's well
under 0.050"
Doug Leithauser

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Mail From: "Ronak, TP (Timothy)" <(email redacted)>

Arnie,
My suggestion would be to ensure that the studs are not pulling out of the
head. Put a straight end along all of the studs. I assume you have a stock
260 head with the correct adjustable rockers that DO NOT have the provision
to align on the valve stem tip. They are flat where the contact the top of
the valve. I would check Valve to piston clearance and valve spring coil
bind. I would also check whether you can fit a .010 feeler gauge between the
coils of the valve spring at max lift. Why it would show up after 300 miles
I have no idea but it sounds as though you will need to recheck everything
to diagnose it. The other option is to just stick in some new pushrods and
away you go. It is also important to ensure that the pushrods are such that
the guide "slots" in the heads are not worn. If they are or if the engine
builder did not ensure that the rockers ride directly over the valve stem
tip it could have widened the slot enough to alter the geometry enough that
the pushrod bound and bent.
Another possibility is that the slot in the rockers is not long enough for
the cam you are using and may bind slightly. Look at the ends of the slot on
the rockers or the stud itself for contact.
Do not rule out a delayed failure as I used to street race my car late at
night and have a great night racing, drive home and then get up the
following day and on the way to work about 40 minutes from home a rocker
would just break half way there due to the bind. I also did it with
pushrods. It may be something similar. Be specific about what your
combination is and perhaps it may give a clue.
The fact that it is 2 intake valves indicates that they may have touched a
piston.

Best Regards,

Tim Ronak
Business Development Manager
Akzo Nobel Coatings
Off: (949) 305-5393
Fx: (949) 305-5394
Cell: (949) 439-4784
email: (email redacted)
VM: (800) 234-6747 ext. 2257#

This message, including attachments, is confidential and may be privileged.
If you are not an intended recipient, please notify the sender then delete
and destroy the original message and all copies. You should not copy,
forward and/or disclose this message, in whole or in part, without
permission of the sender.