I just got a rebuilt rochester q-jet non CC carb(for free!), it looks great and runs good, but it doesnt have a break vacum on the bottom plate (back of carb). So I have my stock qjet w/ the break vacum and was wondering if I could just switch the bottem plates w/ out any problems? I would do the swap now but I know its a lil pain to replace those plates and my TA is my only (running) car



C-ya


PS: I have the distributer changed to vacum also, so theres no problems w/ CC

 

The bases won't swap.

Check this site: http://www.carbs.net/Quads/E4MC.htm

Does this new carb have #55? If so, you don't need #320, necessarily. My CC carb only has #55, I have a carb off my van that only has #320. I've never had one with both, although I know they did exist. But, if it only came with one, it only needs one.

 

This carb has 2, #55 and #320, I wonder why they have 2, my friends carb also has 2.

So what'll happen if I tried switching baseplates? just not gonna fit? or just wont work?

Anyways ill try looking for another base plate. This carb is from 1972 off a 350, LoL runs great but I can't stop to easily w/ out the breakvacum. I think my cousin has one that'll fit. Well Thanks agian.

 

I think I completely misunderstood what you were saying. I thought you were talking about the choke pull-off(s), which are sometimes called vacuum breaks.

I think what you're asking is actually about the vacuum source for the power brakes (what a difference the order of a few letters in a word can make). You're looking for a port to attach it to, right?

If that's the case, use the port in the intake runner behind the carb. You'll probably have to get a different fitting with a larger nipple on it than what's on there now, but they are available. You can tee the other things that are attached to it now in with the power brake line.

Are you sure the carb base doesn't have a port in it? They sometimes have a plug that is flush to the edge of the throttle plate.

 

Short answer- forget the second (rear) vacuum break. Leave it off and never look back.

Reason it existed: emissions. The stock front can opens at a certain rate which can't be changed once set. Set it too slow and the car floods out on a cold start (high emissions). Set it too fast and it leans out immediately after a cold start (high emissions again). The 2 vacuum break system was developed so that the front break would pop the choke open quickly just a little bit to keep from flooding out without going lean and stalling. The rear break pulls back much more slowly and would pop the choke open just a little bit more than the first very soon after when the now-started motor could tolerate a slightly leaner mix. This is a tight balancing act that you probably don't want to deal with on a performance-oriented motor. Not that it can't be made to work and work well, but it's one more thing to deal with that isn't strictly necessary and only makes a very minor difference in the engine's performance and only immediately after cold startup.

 

LoL yea I was kinda wondering why you were talking about chokes and stuff. But it was my fault for not spelling it right.

Never got A's in spelling... LoL

Well thanks for the advice, gonna check out the parts store tomarrow.
C-ya