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73-87 Chevy _ GMC Trucks => Engine/Drivetrain => Topic started by: JohnnyPopper on November 07, 2023, 08:55:48 pm

Title: Vacuum Routing Troubles...
Post by: JohnnyPopper on November 07, 2023, 08:55:48 pm
I read extensively through the manual for my '78 K10, trying to figure out the vacuum routing of my engine so as to re-engage the EGR system and Timing vac advance.

BTW, It is a '78 K10, 350, full smog i.e. EGR, Diverter, EFE valve, and the heat/stove riser in the air cleaner (thermAC?), which name escapes me... There is no dashpot at the carb, just a solenoid tied to voltage with the AC compressor.

It doesn't match exactly to any of the diagrams in 6E.

Purple 2 port is in the manifold. A Green 2 port with what looks like it has a filtered port? is in the T-stat housing along with a blue 2 port. 

Any help would be greatly appreciated!
Title: Re: Vacuum Routing Troubles...
Post by: bd on November 07, 2023, 10:58:39 pm
If you don't have the original emissions sticker on the air cleaner housing or radiator support and no one else posts an applicable diagram, do the best you can using Fig 6E-8.
Title: Re: Vacuum Routing Troubles...
Post by: JohnnyPopper on November 08, 2023, 11:47:37 am
Thanks bd!

Any thoughts on the vac ports? I have a Qjet and my best guess is the left to right ports are correct as far as plumbing the vac lines.
Title: Re: Vacuum Routing Troubles...
Post by: VileZambonie on November 08, 2023, 04:03:59 pm
Is your VECI label intact? Is the 2 letter code visible? I'm attaching applicable 78 k10 diagrams. Also, the 1980 diagrams are here which should be helpful for references http://forum.73-87chevytrucks.com/smforum/index.php?topic=37085.0
Title: Re: Vacuum Routing Troubles...
Post by: JohnnyPopper on November 08, 2023, 07:45:26 pm
Thanks guys!

No sticker left on the air cleaner.

There is a partial on the top of the core support. Is that the VECI? If yes, where would the code be?
Title: Re: Vacuum Routing Troubles...
Post by: JohnnyPopper on November 11, 2023, 07:59:55 pm
So with the motor at operating temp, I tested the condition of the 3 TVS's.

Purple, in the T-state housing OPEN

Green, also in housing CLOSED

Blue, in manifold OPEN

Assuming the opposite is true when cold, I can try to figure which TVS goes to what VAC circuit...Here's to hoping... :-\