76 problem - advice requested.

I have a 1976 vette with about 120K miles on it. Owned it since new.

Last year I had to do a fair amount of work on it (spring, shocks, rad
support bracket, new rad, new water pump.).

It seems to have been developing a problem and I am not sure what it
is.

I thought it started about the time I installed the new water pump,
but that could be nothing more than sheer coincidence. It was making a
sort of slight rubbing/banging/knocking noise, and I thought it was
some minor machining discrepency causing a slight rubbing of the water
and main pulleys. There was a rubbing sound that went away after a
bit.

Yesterday I had to replace a motor mount and tightened a bit of
exhaust on the manifold.

Today the noise is back. But now It sounds more like a banging/
knocking
sound. The frequency increases with engine RPM. If I bring the engine
up to a modest rpm and hold it there , it seems to go away. It seems
worse when I first start it.

Now I am obviously not expecting a thorough diagnostic from this
description, but I am not a very experienced mechanic. Does it sounds
like the symptoms of a main/crank bearing or something terminal of
that nature? If so, I'm afraid old Betsy is doomed because I do not
have the facilities nor the resources to get it repaired ......

FWIW, it still seems to run ok, oil pressure is normal, battery
charging, water temp, shifting etc.... I went around it with a crowbar
and using it on my ear as a poor man's stethoscope and was unable to
pinpoint the source of the problem (so far)... It definitely seems to
be coming from the bottom part of the front/engine somewhere.....

Thanks for any input.

wrote:
> I have a 1976 vette with about 120K miles on it. Owned it since new.
>
> Last year I had to do a fair amount of work on it (spring, shocks, rad
> support bracket, new rad, new water pump.).
>
> It seems to have been developing a problem and I am not sure what it
> is.
>
> I thought it started about the time I installed the new water pump,
> but that could be nothing more than sheer coincidence. It was making a
> sort of slight rubbing/banging/knocking noise, and I thought it was
> some minor machining discrepency causing a slight rubbing of the water
> and main pulleys. There was a rubbing sound that went away after a
> bit.
>
> Yesterday I had to replace a motor mount and tightened a bit of
> exhaust on the manifold.
>
> Today the noise is back. But now It sounds more like a banging/
> knocking
> sound. The frequency increases with engine RPM. If I bring the engine
> up to a modest rpm and hold it there , it seems to go away. It seems
> worse when I first start it.
>
> Now I am obviously not expecting a thorough diagnostic from this
> description, but I am not a very experienced mechanic. Does it sounds
> like the symptoms of a main/crank bearing or something terminal of
> that nature? If so, I'm afraid old Betsy is doomed because I do not
> have the facilities nor the resources to get it repaired ......
>
> FWIW, it still seems to run ok, oil pressure is normal, battery
> charging, water temp, shifting etc.... I went around it with a crowbar
> and using it on my ear as a poor man's stethoscope and was unable to
> pinpoint the source of the problem (so far)... It definitely seems to
> be coming from the bottom part of the front/engine somewhere.....
>
> Thanks for any input.

On my '71 at about 75,000 miles, the vibration damper worked its way to
the point where it was rubbing. It had to be replaced. That is a long
time ago. Man, I miss that car.

Rather than a crowbar, I use a flexible piece of hose. Old pool vacuum
hose is nice, as it is about 2 inches in diameter. I'd bet a piece of
garden hose would work also.

Hope this helps.
--

Jim ( '93 40th Anniversary )

On Jul 9, 2:15*pm, Jim H > wrote:
> wrote:
> > I have a 1976 vette with about 120K miles on it. Owned it since new.
>
> > Last year I had to do a fair amount of work on it (spring, shocks, rad
> > support bracket, new rad, new water pump.).
>
> > It seems to have been developing a problem and I am not sure what it
> > is.
>
> > I thought it started about the time I installed the new water pump,
> > but that could be nothing more than sheer coincidence. It was making a
> > sort of slight rubbing/banging/knocking noise, and I thought it was
> > some minor machining discrepency causing a slight rubbing of the water
> > and main pulleys. There was a rubbing sound that went away after a
> > bit.
>
> > Yesterday I had to replace a motor mount and tightened a bit of
> > exhaust on the manifold.
>
> > Today the noise is back. But now It sounds more like a banging/
> > knocking
> > sound. The frequency increases with engine RPM. If I bring the engine
> > up to a modest rpm and hold it there , it seems to go away. It seems
> > worse when I first start it.
>
> > Now I am obviously not expecting a thorough diagnostic from this
> > description, but I am not a very experienced mechanic. Does it sounds
> > like the symptoms of a main/crank bearing or something terminal of
> > that nature? If so, I'm afraid old Betsy is doomed because I do not
> > have the facilities nor the resources to get it repaired ......
>
> > FWIW, it still seems to run ok, oil pressure is normal, battery
> > charging, water temp, shifting etc.... I went around it with a crowbar
> > and using it on my ear as a poor man's stethoscope and was unable to
> > pinpoint the source of the problem (so far)... It definitely seems to
> > be coming from the bottom part of the front/engine somewhere.....
>
> > Thanks for any input.
>
> On my '71 at about 75,000 miles, the vibration damper worked its way to
> the point where it was rubbing. It had to be replaced. That is a long
> time ago. Man, I miss that car.
>
> Rather than a crowbar, I use a flexible piece of hose. Old pool vacuum
> hose is nice, as it is about 2 inches in diameter. I'd bet a piece of
> garden hose would work also.
>
> Hope this helps.
> --
>
> Jim ( '93 40th Anniversary )

hmm -If I am looking at the right part, when running it does not
*seem* to run off center,
but it does seem like the area where the noise is located (at least
generallyt). I will have to try that swimming pool hose trick
to see if I can further narrow it down (without lopping something off
in all the turning and whirling things in that area....)

I wonder if it would be made worse by disconnecting the a/c drive
belt? I did that
since the A/c is not working and I only use it for scooting around
with the top out. That make it pull more to one side and like you say
- a 35 year old piece of rubber ...... maybe there is hope yet .....

Is that what the service manual would call a torsional damper? I have
the factory service manuals here to help me along with things, but
like I say, I am not a horribly experienced mechanic....

thanks

> wrote in message
...
>I have a 1976 vette with about 120K miles on it. Owned it since new.
>
> Last year I had to do a fair amount of work on it (spring, shocks,
> rad
> support bracket, new rad, new water pump.).
>
> It seems to have been developing a problem and I am not sure what it
> is.
>
> I thought it started about the time I installed the new water pump,
> but that could be nothing more than sheer coincidence. It was making
> a
> sort of slight rubbing/banging/knocking noise, and I thought it was
> some minor machining discrepency causing a slight rubbing of the
> water
> and main pulleys. There was a rubbing sound that went away after a
> bit.
>
> Yesterday I had to replace a motor mount and tightened a bit of
> exhaust on the manifold.
>
> Today the noise is back. But now It sounds more like a banging/
> knocking
> sound. The frequency increases with engine RPM. If I bring the
> engine
> up to a modest rpm and hold it there , it seems to go away. It seems
> worse when I first start it.
>
> Now I am obviously not expecting a thorough diagnostic from this
> description, but I am not a very experienced mechanic. Does it
> sounds
> like the symptoms of a main/crank bearing or something terminal of
> that nature? If so, I'm afraid old Betsy is doomed because I do not
> have the facilities nor the resources to get it repaired ......
>
> FWIW, it still seems to run ok, oil pressure is normal, battery
> charging, water temp, shifting etc.... I went around it with a
> crowbar
> and using it on my ear as a poor man's stethoscope and was unable to
> pinpoint the source of the problem (so far)... It definitely seems
> to
> be coming from the bottom part of the front/engine somewhere.....
>
> Thanks for any input.

May very well be your new water pump, easy to check by removing the
belt and starting it up for a bit. It could just be your fan clutch
and your engine can be run without it for some time if you keep it
moving. Main bearings that are making a noise don't go away, they just
get worse.

I would certainly look at what you just worked on first if it came
right after that effort. Don't neglect the harmonic balancer, the
inertia rings do come loose at times. Someone had replaced the
steering idler arm on my '64 and had one with a zerk fitting that was
hitting the exhaust pipe that made you think rods were knocking. It to
would change the knock with engine RPM.

As a make shift stethoscope I use a tubular golf club handle, head
removed, to pinpoint the noise. The soft grip is easy on the ear. ;-))

Good luck and let use know what you find.

On Jul 9, 4:49*pm, "Dad" > wrote:
> > wrote in message
>
> ...
>
>
>
> >I have a 1976 vette with about 120K miles on it. Owned it since new.
>
> > Last year I had to do a fair amount of work on it (spring, shocks,
> > rad
> > support bracket, new rad, new water pump.).
>
> > It seems to have been developing a problem and I am not sure what it
> > is.
>
> > I thought it started about the time I installed the new water pump,
> > but that could be nothing more than sheer coincidence. It was making
> > a
> > sort of slight rubbing/banging/knocking noise, and I thought it was
> > some minor machining discrepency causing a slight rubbing of the
> > water
> > and main pulleys. There was a rubbing sound that went away after a
> > bit.
>
> > Yesterday I had to replace a motor mount and tightened a bit of
> > exhaust on the manifold.
>
> > Today the noise is back. But now It sounds more like a banging/
> > knocking
> > sound. The frequency increases with engine RPM. If I bring the
> > engine
> > up to a modest rpm and hold it there , it seems to go away. It seems
> > worse when I first start it.
>
> > Now I am obviously not expecting a thorough diagnostic from this
> > description, but I am not a very experienced mechanic. Does it
> > sounds
> > like the symptoms of a main/crank bearing or something terminal of
> > that nature? If so, I'm afraid old Betsy is doomed because I do not
> > have the facilities nor the resources to get it repaired ......
>
> > FWIW, it still seems to run ok, oil pressure is normal, battery
> > charging, water temp, shifting etc.... I went around it with a
> > crowbar
> > and using it on my ear as a poor man's stethoscope and was unable to
> > pinpoint the source of the problem (so far)... It definitely seems
> > to
> > be coming from the bottom part of the front/engine somewhere.....
>
> > Thanks for any input.
>
> May very well be your new water pump, easy to check by removing the
> belt and starting it up for a bit. It could just be your fan clutch
> and your engine can be run without it for some time if you keep it
> moving. Main bearings that are making a noise don't go away, they just
> get *worse.
>
> I would certainly look at what you just worked on first if it came
> right after that effort. Don't neglect the harmonic balancer, the
> inertia rings do come loose at times. Someone had replaced the
> steering idler arm on my '64 and had one with a zerk fitting that was
> hitting the exhaust pipe that made you think rods were knocking. It to
> would change the knock with engine RPM.
>
> As a make shift stethoscope I use a tubular golf club handle, head
> removed, to pinpoint the noise. The soft grip is easy on the ear. ;-))
>
> Good luck and let use know what you find.

Thanks - it will take me a few days to get to it due to other things
going on here.
I think I will take off the fan and all belts so I can get in there
with better safety with
a chunk of pool hose to see what I may be able to determine....

Keep you posted......

BSA

That many miles has in the past caused the fuel pump pushrod to wear
and cause the type noise you are hearing. Try getting something (golf
club, hose, whatever) on the fuel pump and you will probably hear the
slap, knock of the rod. Not too hard to repair nor too expensive.
There is a bolt in the front of the block that can be removed that
normally holds nothing but, if you screw a longer bolt just snug it
holds the rod in place while you remove and then to replace the pump.
Before the bolt hole was cast into the block it was a real pain to do.
Get a new rod, gaskets for pump and mounting plate and some gasket
cement and go for it.

Good luck
PDDeen


On Jul 9, 3:49*pm, "Dad" > wrote:
> > wrote in message
>
> ...
>
>
>
>
>
> >I have a 1976 vette with about 120K miles on it. Owned it since new.
>
> > Last year I had to do a fair amount of work on it (spring, shocks,
> > rad
> > support bracket, new rad, new water pump.).
>
> > It seems to have been developing a problem and I am not sure what it
> > is.
>
> > I thought it started about the time I installed the new water pump,
> > but that could be nothing more than sheer coincidence. It was making
> > a
> > sort of slight rubbing/banging/knocking noise, and I thought it was
> > some minor machining discrepency causing a slight rubbing of the
> > water
> > and main pulleys. There was a rubbing sound that went away after a
> > bit.
>
> > Yesterday I had to replace a motor mount and tightened a bit of
> > exhaust on the manifold.
>
> > Today the noise is back. But now It sounds more like a banging/
> > knocking
> > sound. The frequency increases with engine RPM. If I bring the
> > engine
> > up to a modest rpm and hold it there , it seems to go away. It seems
> > worse when I first start it.
>
> > Now I am obviously not expecting a thorough diagnostic from this
> > description, but I am not a very experienced mechanic. Does it
> > sounds
> > like the symptoms of a main/crank bearing or something terminal of
> > that nature? If so, I'm afraid old Betsy is doomed because I do not
> > have the facilities nor the resources to get it repaired ......
>
> > FWIW, it still seems to run ok, oil pressure is normal, battery
> > charging, water temp, shifting etc.... I went around it with a
> > crowbar
> > and using it on my ear as a poor man's stethoscope and was unable to
> > pinpoint the source of the problem (so far)... It definitely seems
> > to
> > be coming from the bottom part of the front/engine somewhere.....
>
> > Thanks for any input.
>
> May very well be your new water pump, easy to check by removing the
> belt and starting it up for a bit. It could just be your fan clutch
> and your engine can be run without it for some time if you keep it
> moving. Main bearings that are making a noise don't go away, they just
> get *worse.
>
> I would certainly look at what you just worked on first if it came
> right after that effort. Don't neglect the harmonic balancer, the
> inertia rings do come loose at times. Someone had replaced the
> steering idler arm on my '64 and had one with a zerk fitting that was
> hitting the exhaust pipe that made you think rods were knocking. It to
> would change the knock with engine RPM.
>
> As a make shift stethoscope I use a tubular golf club handle, head
> removed, to pinpoint the noise. The soft grip is easy on the ear. ;-))
>
> Good luck and let use know what you find.

"PDDeen" > wrote in message
...
That many miles has in the past caused the fuel pump pushrod to wear
and cause the type noise you are hearing. Try getting something (golf
club, hose, whatever) on the fuel pump and you will probably hear the
slap, knock of the rod. Not too hard to repair nor too expensive.
There is a bolt in the front of the block that can be removed that
normally holds nothing but, if you screw a longer bolt just snug it
holds the rod in place while you remove and then to replace the pump.
Before the bolt hole was cast into the block it was a real pain to do.
Get a new rod, gaskets for pump and mounting plate and some gasket
cement and go for it.

Good luck
PDDeen

Now there's a good one I forgot, been with the electric fuel pumps to
long.
http://www.classiccarauto.com/impala...uel_pump.shtml
Good picture direction although it looks like an old front mounted SBC
so the hole to retain it wasn't/couldn't be used. A new fuel pump and
rod may be in order at this age, yours will have a bigger canister.
Also the hose should be replaced. Fitting wrenches are a must. Both
the fuel pump and the rod from https://www.rockauto.com/ can be less
than $50.

On Jul 10, 9:06*am, "Dad" > wrote:
> "PDDeen" > wrote in message
>
> ...
> That many miles has in the past caused the fuel pump pushrod to wear
> and cause the type noise you are hearing. Try getting something (golf
> club, hose, whatever) on the fuel pump and you will probably hear the
> slap, knock of the rod. Not too hard to repair nor too expensive.
> There is a bolt in the front of the block that can be removed that
> normally holds nothing but, if you screw a longer bolt just snug it
> holds the rod in place while you remove and then to replace the pump.
> Before the bolt hole was cast into the block it was a real pain to do.
> Get a new rod, gaskets for pump and mounting plate and some gasket
> cement and go for it.
>
> Good luck
> PDDeen
>
> Now there's a good one I forgot, been with the electric fuel pumps to
> long.http://www.classiccarauto.com/impala...vy_fuel_pump.s...
> Good picture direction although it looks like an old front mounted SBC
> so the hole to retain it wasn't/couldn't be used. A new fuel pump and
> rod may be in order at this age, yours will have a bigger canister.
> Also the hose should be replaced. Fitting wrenches are a must. Both
> the fuel pump and the rod fromhttps://www.rockauto.com/can be less
> than $50.

Good example of not knowing what all the bolts on an engine are for.
The '64 Impala would have the bolt I referred to as well as the 305
small block. The only one I can not remember seeing it on was a '56
Vette and it may have been because of the engine mount plate.All of
the later mechanical pump engines should have the bolt. It is around
the corner to the front of the block and looks like it has a large
flat washer on it. As I remember it is't a flat washer but is a fiber
washer. Bolt is @ 1/2" and I used a 1" tightened finger tight only. I
just needs to hold the bolt during assembly.


YMMV

Paul

"PDDeen" > wrote in message
...
On Jul 10, 9:06 am, "Dad" > wrote:
> "PDDeen" > wrote in message
>
> ...
> That many miles has in the past caused the fuel pump pushrod to wear
> and cause the type noise you are hearing. Try getting something
> (golf
> club, hose, whatever) on the fuel pump and you will probably hear
> the
> slap, knock of the rod. Not too hard to repair nor too expensive.
> There is a bolt in the front of the block that can be removed that
> normally holds nothing but, if you screw a longer bolt just snug it
> holds the rod in place while you remove and then to replace the
> pump.
> Before the bolt hole was cast into the block it was a real pain to
> do.
> Get a new rod, gaskets for pump and mounting plate and some gasket
> cement and go for it.
>
> Good luck
> PDDeen
>
> Now there's a good one I forgot, been with the electric fuel pumps
> to
> long.http://www.classiccarauto.com/impala...vy_fuel_pump.s...
> Good picture direction although it looks like an old front mounted
> SBC
> so the hole to retain it wasn't/couldn't be used. A new fuel pump
> and
> rod may be in order at this age, yours will have a bigger canister.
> Also the hose should be replaced. Fitting wrenches are a must. Both
> the fuel pump and the rod fromhttps://www.rockauto.com/can be less
> than $50.

Good example of not knowing what all the bolts on an engine are for.
The '64 Impala would have the bolt I referred to as well as the 305
small block. The only one I can not remember seeing it on was a '56
Vette and it may have been because of the engine mount plate.All of
the later mechanical pump engines should have the bolt. It is around
the corner to the front of the block and looks like it has a large
flat washer on it. As I remember it is't a flat washer but is a fiber
washer. Bolt is @ 1/2" and I used a 1" tightened finger tight only. I
just needs to hold the bolt during assembly.


YMMV

Paul

That's what intrigued me about the pictures in the repair site. As far
as I know the only front mount SBC was '55, '56, and '57. The Impala
didn't exist then. Strange pictures with the wood frame and all. I
never had to use that bolt to retain the push rod but only changed 4
or 5, the last being on a '73 Chevy van while on vacation.

On Jul 10, 9:04*pm, "Dad" > wrote:
> "PDDeen" > wrote in message
>
> ...
> On Jul 10, 9:06 am, "Dad" > wrote:
>
>
>
> > "PDDeen" > wrote in message
>
> ...
> > That many miles has in the past caused the fuel pump pushrod to wear
> > and cause the type noise you are hearing. Try getting something
> > (golf
> > club, hose, whatever) on the fuel pump and you will probably hear
> > the
> > slap, knock of the rod. Not too hard to repair nor too expensive.
> > There is a bolt in the front of the block that can be removed that
> > normally holds nothing but, if you screw a longer bolt just snug it
> > holds the rod in place while you remove and then to replace the
> > pump.
> > Before the bolt hole was cast into the block it was a real pain to
> > do.
> > Get a new rod, gaskets for pump and mounting plate and some gasket
> > cement and go for it.
>
> > Good luck
> > PDDeen
>
> > Now there's a good one I forgot, been with the electric fuel pumps
> > to
> > long.http://www.classiccarauto.com/impala...vy_fuel_pump.s...
> > Good picture direction although it looks like an old front mounted
> > SBC
> > so the hole to retain it wasn't/couldn't be used. A new fuel pump
> > and
> > rod may be in order at this age, yours will have a bigger canister.
> > Also the hose should be replaced. Fitting wrenches are a must. Both
> > the fuel pump and the rod fromhttps://www.rockauto.com/canbe less
> > than $50.
>
> Good example of not knowing what all the bolts on an engine are for.
> The '64 Impala would have the bolt I referred to as well as the 305
> small block. The only one I can not remember seeing it on was a '56
> Vette and it may have been because of the engine mount plate.All of
> the later mechanical pump engines should have the bolt. It is around
> the corner to the front of the block and looks like it has a large
> flat washer on it. As I remember it is't a flat washer but is a fiber
> washer. Bolt is @ 1/2" and I used a 1" tightened finger tight only. I
> just needs to hold the bolt during assembly.
>
> YMMV
>
> Paul
>
> That's what intrigued me about the pictures in the repair site. As far
> as I know the only front mount SBC was '55, '56, and '57. The Impala
> didn't exist then. Strange pictures with the wood frame and all. I
> never had to use that bolt to retain the push rod but only changed 4
> or 5, the last being on a '73 Chevy van while on vacation.


Sorry it took me awhile to find time to get to it, but ....

Well, well, well - here's the skinny!

I disconnected all the belts and fired it up and it makes normal
noises for a 35 year old engine!

I hooked them up one by one and the noise was still gone. However,
more closely examining everything, the head of the bottom mounting
bolt for the power steering pump has snapped off. That allows some
degree of movement and hence the clanking noises I hear I think.

Trying to remove it, it is in a different position so does not seem to
wiggle. I fired it up and sure enough - the noise seems to have gone
away.

Now to effect a permanent fix, I need to see if that bottom bolt
screws into the mount assembly somehow or whether it can be punched
out. Looks like I may have to disconnect and remove the power steering
pump.

If I can do that and the noise has disappeared for good, I am a happy
camper, but I will not know until I get there I guess.....