39 minutes ago, chaseincats said:

You do not need to seal the car, just having the vacuum on is good enough (my doors and windows were open for example).

This surprises me.  When we do smoke testing at work, we seal it up tight.  We cut cardboard to fit the driver's door window and that gets taped on tight.  The inside guy then climbs into the trunk/hatch area with a flashlight and a 2-way radio so he can direct the smoke machine guy to all the possible leak paths.

In our case, we are dealing with very small leaks, so it takes a bit of time to make sure everything is sealed tight.  Even brand new cars with modern sealing will still leak around tail light gaskets, trim holes, and wiring grommets.  I can only imagine how bad the average 45 - 50 year old car leaks.  

40 minutes ago, Jeff G 78 said:

This surprises me.  When we do smoke testing at work, we seal it up tight.  We cut cardboard to fit the driver's door window and that gets taped on tight.  The inside guy then climbs into the trunk/hatch area with a flashlight and a 2-way radio so he can direct the smoke machine guy to all the possible leak paths.

In our case, we are dealing with very small leaks, so it takes a bit of time to make sure everything is sealed tight.  Even brand new cars with modern sealing will still leak around tail light gaskets, trim holes, and wiring grommets.  I can only imagine how bad the average 45 - 50 year old car leaks.  

Absolutely agree, just passing on what we did/worked

I reinstalled an old, crappy trim panel I had from a parts car.  The once black vinyl has blue overspray and the butyl isn't really sticky, but it HAS to be better than nothing.  I didn't want to install my good black panel yet.  I'll know tomorrow if it helps at all.

2 minutes ago, Jeff G 78 said:

I reinstalled an old, crappy trim panel I had from a parts car.  The once black vinyl has blue overspray and the butyl isn't really sticky, but it HAS to be better than nothing.  I didn't want to install my good black panel yet.  I'll know tomorrow if it helps at all.

The trim panel is not going to do you any good unless you seal the metal opening behind it as the piece won't be airtight even when bolted down.  Get a bunch of duct or painters tape and seal that opening in the hatch then poke holes in the tape where the trim screws are going to go - that's the only way to be sure its air-tight.