wicked squeaks, possibly TPEFI related

[Clare Snyder]

>I've got a weird one here. Every one I've asked so far has been stomped. I
>drove my '89 5.7L TPI '58 chevy truck to Atlanta last weekend, 100mph
>plus...420 miles one way from my home...so I'm perty sure it's not a
>mechanical engine noise. The following is what I know. I think it's the EGR
>valve or diaphragm resonating.
>
>When the engine is hot (just after getting off the highway) I get this high
>pitch squeaking sound. Sounds like a belt but much louder. I can hear it 100
>yards off.  Changed the belt, operated the engine with the belt off, added
>many cans of belt dressing, and the engine still squeaks. 
>
>Swapped trannys and inspected the flywheel. Flywheel a-ok, still got the
>squeaks.
>
>Check this out, I can pull the engine oil dip stick when it's squeaking and
>magicly, it stops. That's why I think it might be EGR related. The EGR valve
>vacuume line is disconnected. The truck stumbles bad when it's connected. I
>suspect the diaphram is leaking. I can't pull vacuume in it if the engine is
>running. Pulls ok when the engine is off.
>
>By now, I'm desperate to stop this damn squeaking so I connected a vacuume
>gage to the engine dip stick tube to see why it would affect the engine
>squeak. Here is what I found.
>
>9.5"    engine idle, park, no squeak
>11.5"   engine idle, Drive, light squeak
>13.0"   engine idle, park, Loud squeak
>9.5"    engine idle, park, no squeak, after pulling the engine dip stick to
>'break vacuume'
>
>9.5"    engine idle, park, no squeak
>11.5"   engine idle, Drive, light squeak
>13.0"   engine idle, park, Loud squeak
>9.5"    engine idle, park, no squeak, after winging the throttle and reving
>engine to ~3,000rpm quickly
>
>Manifold vauume was 18" - 18.5" at idle and 17" in gear. 
>
>What ever is causing the squeak is definitly vacumme related. I checked both
>PVC vales, clean as a wistle and free.  The evidence suggest that there is a
>ported vacuume leak from the manifold to the crankcase and that the vacuume
>is held untill you pull the dip stick or kill the motor. I have all but
>given up on finding the root cause of this irritating noise. If you guys
>don't give a solution, I will be forced to treat the symptom rather than
>solve the problem. I'll install a vacuume breaker that relieves crankcase
>vacuume at 10"  If it turns out that this is not EFI related, feel free to
>E-mail me personally...somebody somewhere has had this problem or is having it.
>
>thanks in advance for any solution offered,
>GMD
>
>"Irritating sounds and actions can drive a man to do insane things"
>George M. Dailey
>gmd at tecinfo.com
>
>
Sounds to me like you have an intake manifold leak, drawing into the
crankcase. This is applying a vacuum to the crankcase, and the leak makes
EGR unuseable due to over-lean mixture. Just a (somewhat educated) guess,
but if you have pulled the tranny, the intake should be a cinch. Before
going this far, however, check your crankcase ventilation (PCV) system.