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Hi all, new here. I have a 75 corvette, bought in 77. Everything is original. I would like to replace the carb. and clean up the air pump which quit working years ago. The carb. is a Rochester and would like to go back with maybe an Edelbrock 600. The existing carb. has vacuum hose's going to the choke, (its not electric) but I am having problems matching that one up. Also wondering which hoses from the air pump to remove or cap? Tks in advance.
From: At my Bar drinking and wrenching in Lafayette Colorado
Why in the world would you replace your high performance 750 cfm carb with an old, obsolete 600 cfm Carter AFB that GM deemed to be obsolete after 1966.?? ...And those are not vacuum hoses going to your choke - it's the hot air system. Sounds like you should educate yourself a little bit about the carb subject before you seriously screw up your car. Of course, if your car is too fast with the Q-Jet on it, use the old AFB carb - it is good for a solid 15 hp decrease in performance.
Welcome to the forum. If your carb is truly the original, follow Lars' advice to not downgrade it; have it rebuilt. (He is a true expert in rebuilding and, dare I say, blueprinting them for peak performance. He's also been writing and collaborating on this topic for decades so knows of what he speaks.) If you decide a replacement is in order, don't throw away or trade in your original carb! Offer it up here if you want to sell it.
I have mentioned here and still cringe at the amount of good Q-Jets that are replaced by Edelbrock 600's from the auto parts store. The only way to mount one to a Q-jet intake is with the dreaded square to spread bore four hole adapter.......this POS is responsible for thousands of classic cars that run like s%&t......the primary mismatch is so terrible that there is no good way to tune any carb on the street correctly with it......
Last year I removed a 600 Edelbrock from a stockish 72' Corvette and replaced with one of my Q-Jets with an electric choke. This car went from stumbling, lack of power and response off idle to being able to turn the tires from a roll in first gear.......part of this was the curve I put in the distributor......he also picked up about 100 miles per tankful with it.
If your Q-Jet is original and unmolested.......have it refurbished by a professional like Lars or Cliff Ruggles.....
Takes some pics of the motor with the air cleaner off and post them here......we can tell a lot from them.
You can removed all of the air pump assembly and cap the tubes off.....yes.......someone makes the caps but forgot who.
If you really want an improvement.....have the carb gone through, curve the distributor, and install long tube headers with true duals.......you will pick up a bunch.....it will be more efficient and responsive....
Tks all for the replies, the NAPA auto guy was hinting around about having it rebuilt, so yes I will go that route. If Lars or Cliff have a web site or email address it would be appreciated. Pictures attached.
Looks like a decent carburetor for a good setup!
I would like to make a couple recommendations before you remove it.
The brake booster pipe is not being reproduced and are getting hard to find.
Put a couple rags under the pipe nut and carburetor bushing, apply some good penetrating spray (Kroil or PB Blaster) around where the pipe nut rotates around the pipe, just a shot or two and let it sit a few hours then apply again. Yellow Arrow
Before you do go to remove the pipe, remove the single attaching screw at the throttle cable support bracket. Red Arrow
Doing this first you can see if the pipe is starting to twist at the support and will prevent the spot-weld in the thin tin support to rip.
I have seen many of these pipes destroyed.
Use 2 wrenches.
Do the same process for your fuel line,
And use 2 wrenches
Nice Car!
Thank you! Yea I started to take it off and the fuel line was not being cooperative, I sprayed it and will resume tomorrow. Sending to Lars for rebuild. Really appreciate the feedback and advice! That would of been a huge mistake to buy the Edelbrock if I had a original carb. which was rebuildable.
From: At my Bar drinking and wrenching in Lafayette Colorado
Spray on the nut isn't going to do anything. You just need to use the correct flarenut wrench on the 5/8 fuel line nut and a 1" open end on the inlet nut and put a bunch of force on it. Never attempt to do it with an open end wrench - use a flarenut wrench. Buy one if you don't have one.
From: At my Bar drinking and wrenching in Lafayette Colorado
I have received Tom's carb, and it is a beautiful, pristine example of a near-perfect 1975 Vette Q-Jet. Completely unmolested, and in great rebuildable condition. Some minor problems with a defective rear pulloff, vacuum leaks, a low float level, and other normal setup issues. The carb is going through final cleanup and detail prior to final assembly. This thing should come out looking nice, and is going to run really well. Photos of the test-run to follow...
Lars
air pump and carburetor
