Bad distirbutor?

[Tazman]

Does a distributor go all of a sudden or are there signs to look for? I ask because when my TBI 350 gets warm the tach will fluctuate under load.

[VileZambonie]

Curious why you think the distributor is at fault? Is just the tach malfunctioning?

[hatzie]

HEI distributors don't "Go Bad".  If there are issues you can repair or completely re-build them to last another 40 + years for not much more than the cheap Chinese rebuilds the parts stores will sell you. 
Fluctuating tach after warmup could be several different problems.  Is the Factory tach signal filter still in place?

[Tazman]

Curious why you think the distributor is at fault? Is just the tach malfunctioning?

When it fluctuates the idle changes and can cause the truck to stutter.

[Tazman]

HEI distributors don't "Go Bad".  If there are issues you can repair or completely re-build them to last another 40 + years for not much more than the cheap Chinese rebuilds the parts stores will sell you. 
Fluctuating tach after warmup could be several different problems.  Is the Factory tach signal filter still in place?

No it is an Auto meter tach.

[Irish_Alley]

so what youre saying is the engine rpms are fluctuating and the tach is picking it up. sounds like an electronic issue but it maybe out of the distributor

http://forum.73-87chevytrucks.com/smforum/index.php?topic=29996.0

is it at a certain speed? or only with a hot or cold engine?

[Tazman]

When warm only.

[Irish_Alley]

check engine light on? does it even come on when you put the key in the ignition "on" without the engine running?

[Tazman]

No lights came on during this.

[Irish_Alley]

might have a bulb out. if you can get it working then you might be able to pull a code from it

[Tazman]

I believe the issue has been found. I have a vacuum leak from one of the corners of the intake manifold. So a new gasket will be put in the next free time I get. I will replace the one on the throttle body as well.
Thanks