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2 barrel to 4 barrel carb swap on 1971 cutlass 350
Hi, I had just started the swap with a OEM Rochester 4 barrel and the edelbrock performer 7111, and now having all the parts on, and a new throttle cable bracket, but when I went to start it, it will either not turn over or start and run at a 3-4000rpm idle and die out after 3-5seconds. In some cases when tinkering with the air fuel mixture I would get backfire through the carburetor. I had been surfing the internet for vacuum line diagrams and even a chilton book but cannot find any, I believe I have all my vacuum lines attached to the correct ports, I had also never taken off the distributor to change out the intake manifolds. Just looking for someone that has done the swap that maybe I do need to alter the timing or if you see any hoses I may have in the wrong place. Stuck at a cross road and not sure where else to look.
You have a hot air choke that's not/can't be connected to anything using that manifold. You need an electric choke conversion kit. If you want to get it running the way it is, back off the idle adj scew on the right side of the cab and wire the choke open.
If you can get the choke plate open for a bit, even with a screw driver or something else,you might see some improvements enough to get it started and do some other tuning.
If I were you, I'd loosen the three screws on the choke housing and take some tension off the spring by rotating it. It'll be easier to keep the choke open with what ever you choose to stick n there...
Last edited by don71; October 12th, 2019 at 09:09 PM.
Reason: bla bla moocho
You may have had a tremendous vacuum leak from the bracket being mounted under the flange preventing the engine from idling correctly. With the choke propped open, will it start and idle now?
You may have had a tremendous vacuum leak from the bracket being mounted under the flange preventing the engine from idling correctly. With the choke propped open, will it start and idle now?
I had loosened the three screws and turned it open to where it stands vertical now, it is now at a point where it has a little pop or two like it wants to start and on the third crank a flame came back up through the carburetor. Could be the bracket where I may have to put it on top of the flange since it uses the two rear bolts for the carb to mount the bracket on.
Check your firing order and make sure you are not 180 out on the distributor. Olds is wired CCW.
I had never unplugged any of the spark plug wires so they are still the same as when it was running before with the old manifold and carburetor. Unless it is a different firing order now for the new carb, which I have no looked up yet.
I would check to see if the cap got bumped and its not seated correctly. Make sure the 2 plugs at the cap are seated all the way. Turn the A/F mixture screws all the way in and the open them 4-5 turns each.
The carburetor itself may be bad, my experience has been they are either good or bad. I have taken cars that ran like crap changed the carb and they ran good after. Even rebuilt carbs can be defective. Where did you get it? Was it running ok with the old carburetor?
I would check to see if the cap got bumped and its not seated correctly. Make sure the 2 plugs at the cap are seated all the way. Turn the A/F mixture screws all the way in and the open them 4-5 turns each.
I had noticed you said good catch with the throttle cable bracket and I remember my dad had it running before we had the bracket but the throttle was all over since the cable was not secured will it work better with the bracket above or below the gasket or should I file the bracket so it is thin enough to not raise the carb away on one side
I had noticed you said good catch with the throttle cable bracket and I remember my dad had it running before we had the bracket but the throttle was all over since the cable was not secured will it work better with the bracket above or below the gasket or should I file the bracket so it is thin enough to not raise the carb away on one side
The bracket needs to be bolted ON TOP of the carb flange. Do not put it below the flange, either on top of or beneath the gasket as that will result in a massive vacuum leak.
I had noticed you said good catch with the throttle cable bracket and I remember my dad had it running before we had the bracket but the throttle was all over since the cable was not secured will it work better with the bracket above or below the gasket or should I file the bracket so it is thin enough to not raise the carb away on one side
The answer to the bracket is below, you can install a throttle return spring on the carb to keep it in one place.
Originally Posted by Fun71
The bracket needs to be bolted ON TOP of the carb flange. Do not put it below the flange, either on top of or beneath the gasket as that will result in a massive vacuum leak.
The answer to the bracket is below, you can install a throttle return spring on the carb to keep it in one place.
so it needs to be below in order to run correctly with this throttle cable mount? and to an above question I am using a vacuum gauge from the manifold vacuum port
so it needs to be below in order to run correctly with this throttle cable mount?
NO!
The answer to your question is below, as in it is in the quote belowthis sentence.
Originally Posted by Fun71
The bracket needs to be bolted ON TOP of the carb flange. Do not put it below the flange, either on top of or beneath the gasket as that will result in a massive vacuum leak.
There should not be anything between the carburetor base plate and the intake manifold except the gasket. The gasket's job is to seal the base plate to the intake, so putting the bracket either on top of or below the gasket will prevent a seal and will result in a massive vacuum leak.
The bracket should be on top of the carburetor base plate.
Last edited by Fun71; October 16th, 2019 at 12:47 PM.
so it needs to be below in order to run correctly with this throttle cable mount? and to an above question I am using a vacuum gauge from the manifold vacuum port
Ok, maybe my quote was a bit misleading. No, as Kenneth stated in my "below quote reference" The bracket needs to be attached on top of the carb flange, not sandwiched in between the carb and intake manifold.
Ok, maybe my quote was a bit misleading. No, as Kenneth stated in my "below quote reference" The bracket needs to be attached on top of the carb flange, not sandwiched in between the carb and intake manifold.
After reading it over again changing it around before checking the forum again I had bolted it on top of everything and she runs great I really appreciate all the help on this thread it has been a long couple weeks of frustration with this and it’s awesome to have a community to help
October 12th, 2019, 10:47 AM
2 barrel to 4 barrel carb swap on 1971 cutlass 350
