I picked up a brand new 1980 Thermoquad 9265-s off Craigslist the other day and tried putting it on my mid 70's Chevy 454 but after having problems with vacuum hose routing and finding the right base gasket I decided to put the Edelbrock 1407 back on. After bolting the 1407 back on I had major problems, it will barely start and when it finally started it ran like crap especially after putting it in gear and I only had it off the manifold for 1 hour. The idle dropped considerably and acted like it was running on 5 cylinders. Has anyone had this problem with the 1407 before?

I should mention before trying to switch out the 1407 with the Thermoquad it ran ok, not great but way better than it is now, I'm thinking vacuum leak?

 

The only problem I have had with a 1407 is bog on small engines.

 

I doubt anything went wrong with the carb while it was disconnected.

Things to check:
Vacuum hose is properly connected
Manual choke is set properly
Fuel is getting to the carb

 

Exactly, that's why I'm beyond confused! I finally got it to idle but very high, as soon as I drop it in gear it runs rough for a split second and then dies! The only lines I've got hooked up is the PCV valve and the brake booster, the vacuum advance is hooked to manifold vacuum and the other vacuum ports on the 1407 are plugged. It's all hooked up exactly how it was before I pulled it off. While it was off I sprayed the heck out of it with card cleaner. I've checked for vacuum leaks and have none,

I'M PULLING MY HAIR OUT!

 

Maybe this is the problem... maybe you just moved gunk around and it got somewhere that it shouldn't. Take the rods/jets out and clean (extra easy on the Edelbrock), clean everything again, then reinstall rods/jets... make sure everything else is moving well.

If you want to go a little further:
http://www.instructables.com/id/Clea...-8-Easy-Steps/

 

Sounds like a vacuum leak to me

 

I would take her apart and blow all the passages with compressed air. Probably a piece of crap in the wrong place.

 

Well after taking the adapter plate off and changing the bolts to shorter ones it runs better, not great but better. It still acts like it runs on seven cylinders though. Maybe time for another valve adjustment?