Tiger writers,
Thank you for the suggestions to my engine noise problem.
I received 15 responses, three were very close and one was a bullseye. Bob
Palmer correctly diagonosed this as a vacuum leak through the rear main
seal. The other close answers were crankcase pressure venting on the rear
main. And it turned out, I had made the real mistake by connecting the
valve cover port to a vacuum port on the carb. This created a vacuum in
the crankcase. The dipstick was plugged and there was a good seal
everywhere. The weakest link apparently is the rear main seal which sucked
in air and this created a sqealing noise. Disconnecting the hose from the
valve cover removed the vacuum and eliminated the squeal. Several people
looked at this but did not see it (they were looking at where the noise is
from). The engine tear down was not wasted money, huge things were wrong
inside the engine, but not related to the noise. Interesting, it makes
this noise at low rpm because the throttle is closed and the vacuum is
higher. It does not make the noise until the engine warms up because
without a choke, I have to run the engine faster and open the throttle
more. I suppose the squeal may be the seal rubbing? or is it whistling? it
sure sounds like a squeal vs the high pitch vacuum leaks I've heard before.
Thank you for your suggestions and inputs, it makes this newsgroup work.
Curtis
ps: most entertaining answer!!!
The problem is obvious! You had a mouse trapped in the bellhousing and it was
being rubbed by the teeth on the flywheel. When the rpm was higher the mouse
blacked out - hence no squeal. Somehow, his tail was being pinched by the
valve cover and when the cover was removed the mouse could shift slightly and
not get rubbed. (Don't ask me how his tail reached the valve cover.)
the original puzzler is listed below.
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Listers,
I just finished an odd experience with my new Motorsport 5.0 crate motor.
I purchased the motor last year to install in B9470844. Due to needed
frame repairs and other chassis delays I was not able to install the motor
immediately. I needed to run the motor to fit accessories and select
radiator cooling fan(s) prior to installing in the Tiger. My test stand
has a radiator, cooling fan, oil filter, exhaust system with mufflers, fuel
supply, gauges to monitor oil and temp. After starting the motor a very
odd noise developed. It could best be described as a squeal (like a power
steering pump turned into the limits). The noise came from the rear of the
motor in the bell housing. Although the transmission is connected, there
is no clutch or bearing yet installed. I removed the transmission and the
noise was VERY clearly coming out of the bell housing and it did not come
from any other area. The noise would appear at low rpms and is not
noticeable at higher (>1,200) rpms. I called the shop I bought my motor
through and they came out to examine it. They had never heard anything
like it. They also thought it was the rear of the engine. Previously, I
had removed the stock steel flywheel and installed an aluminum flywheel.
The engine made this noise with the stock flywheel and also with the
aluminum one. They suggested the starter was hung up on the flywheel.
With the transmission removed, you can clearly see the starter is not
engaged. Both flywheels were closely examined and there was no sign of
wear or problem from the starter.
The motor back was taken back for internal inspection. There were several
things wrong internal to the engine (a future post) and the noise was
thought to be the valve springs interference with the rocker arms (a
problem known by Ford). The rockers were replaced with aftermarket brand
roller rockers to eliminate the interference. The engine was cleaned up
internally and reassembled.
I got my motor back from repair, we started it. It ran better than before
(minor improvements inside the engine). However, after the engine warmed
up.... it made the exact same noise it did before.... the same loud squeal
and it occurs at lower rpms not high rpm. I disconnected the drive belt
and confirmed it was not the accessories on the front of the motor. It is
not the alternator, nor the water pump or belt tensioner. On further
investigation.... we were able to find an instance where the motor made
this squeal AFTER THE flywheel stopped turning. Not every time but a few
times. It made this noise for a brief second after the motor was NOT
turning. We did not know that before. Previously, the shop and Ford had
determined the noise was caused by the valve springs rubbing the rocker
arms due to incorrect geometry. That apparently was not the problem. We
were at a loss to find the cause so I called the shop again, they asked if
I could bring the motor in. Yes I could but unless they heard the noise
and could investigate with it running, it would be unlikely they could find
the problem. It looked like I was facing another major engine tear down.
I put the test stand, with radiator, engine, exhaust, fuel supply, battery,
gauges, all. in the truck and hauled it down to the shop. At the shop, I
started the motor and ran it in my truck bed while their mechanics,
prodded, listened, and tried things. They thought it was the starter (I
knew it wasn't) so I shimmed it out. Same. We took off a valve cover and
the noise stopped...... But the valve covers were not the problem, no sign
of interference with the valve train. When the valve cover was replaced,
the noise resumed from the rear of the motor emanating from the bell
housing and only at low rpms. Shortly after that, the mechanics determined
the cause. It turned out to be extremely easy to fix (less than 10
seconds).
I will post the answer in two days. If you can guess the answer, my
compliments to you! This cost me several weeks and $.
Curtis
B9470844
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