Dead Reckon

I'm getting a rebuilt carb next week for $100, q-jet, thermal choke works on it, but on mine the vacuum system is all screwed up and I need a diagram to set it up right.

I know the vacuum should pull on the diaphragm when the engine is cold, closing a valve in the exhaust forcing hot air to the carb, closing the choke. When it's hot, it should not get vacuum. The vacuum tree that is meant to make this work is broken, and unhooked, it was a huge vacuum leak.

However, I have no idea if this is meant to be manifold or ported vacuum, I have no idea how it's supposed to be hooked up, and I have no idea what parts I may be missing. The new carb is complete, it's meant for a '75 vette but it's a drop in replacement.

So if you have a vacuum diagram or can draw one up, please let me know, I don't want to a ton of time getting this set right when I put the new carb on. Also if you know of a good repair manual I can buy that's $30 or less, let me know.

GEARMAN69

Are you referring to the choke pulloff? That must be installed and adjusted properly for the choke to function , as far as heat tubes from intake going into the thermal choke , they should work on the heat alone honestly. Switching to an electric choke on the side of the Qjet is probably the best answer though besides the vaccum pull off working . Some of the pull offs are at the top fronto of carb on choke side but also your may be at the back mounted to the baseplate near the distributer. If your called the EGR valve the diaphram , well that is not what operates the choke. The pull off for the choke should have manifold vacuum (idle and cruise) , the EGR valve can be left with no hose on it if you like until your carb is sorted out. Those eater temp controlled vacuum trees suck, I usually yank it all off and just run direct vacuum to the important places like the modulator (tranny) , distributer advance and choke pull off , that is it.

Dead Reckon

No, this device had a bracket which attached it too the passengers side manifold, I thought it had something to do with the choke, but now I see it doesn't, I don't know what it did except close a valve in the exhaust. It closed the valve when it got vacuum, isn't hooked up or even attached anymore, I'm gonna fix the valve so it's always open (Letting exhaust flow freely out the manifold) and see if I can't remove it later.

Dead Reckon

Let me ask a better question, seeing as I thought I had the choke figured out, but in fact, do not, just how exactly should the choke work on a R4-M4MC Quadrajet? Link below to the exact carb I'm talking about. That's the same kind on my car, and what I am buying.

http://www.carburetion.com/CarbNumbe...Number=7045228

Dead Reckon

Alright I found a vacuum diagram myself, evidently the diaphragm I've been looking at is part of the Early Fuel Evaporation system, and can be deleted, it doesn't do much except warm the engine up faster. It's cheaper to delete it than fix it, the EGR, and just be done with it. There are no sniffers here in Virginia, so I'll be good in that department.

http://repairguide.autozone.com/znet...528007dbf6.gif


The diaphragm is the silver thing in this pic with the vacuum hose on it:

http://i283.photobucket.com/albums/k...y/DSCN0712.jpg

I intend to delete this system, not entirely sure how yet, I'll probably take the valve off, knock the valve portion out, plug it with some bolts, and be done with it.

EDIT: The diaphragm is called a heat valve actuator, it runs off a tree, and the EGR ran off another.