[JJDeville]

I have a 66 GTO Convertible that I bought as an unfinished project. It has a 74 455 engine with 6x-8 heads and a 66 Tripower. I have owned a 64 GTO with Tripower for 30 years that has never gave me any trouble. I bought the car and it would crank and run but I just pulled it into my body shop and started the body and paint on it. My buddy came by yesterday and noticed it had a vacuum fitting on the manifold that was open. I ordered the F connector that goes to the PCV and sealed up the vacuum leak and then it had a more noticeable skip to it. I went through all the basic tune up steps. I set the points, did a compression test, made sure the rocker arms were operating correctly, changed the plugs, with no change in the engine. while it is running, you can pull the plug wires off of the back 2 cylinders(5,7,6, and 8) and there is no change to the running. The new and old plugs will fire off of the plug wire when out of the cylinder. I tightened all of the intake bolts. They were a little loose and the one on the drivers side rear was a little short so I got a longer bolt installed. I cranked it and sprayed starting fluid along the manifold to head area and it did not speed up. I called a friend who also had trouble with a 65 Tripower GTO a while back and he said his problem was the exact same except his 2 front cylinders on each side were dead. He installed a block off plate on the front carburetor location and the car ran fine. I think it must be my rear carb that is causing my trouble. What do you guys think I can do to fix it?

[SRGN]

I think you are on the right track looking at the rear carb. Make sure you have an accelerator pump squirt on that carb when you actuate the throttle, to make sure it's not just a needle and seat stuck closed and blocking fuel flow to the carb.

[TXSTARFIRE]

Could the throttle blades on the rear carb be open a small amount causing a vacuum leak? I believe that the center carb is the one providing fuel during idle.

[JJDeville]

The rear carb is pulling a lot of air like a big vacuum leak and the front carb is not. I took the carb apart and the float was in upside down and the needle and seat was locked down in a closed state and would not move. I am correcting this now but I dont understand what is creating the vacuum leak. I dont see any cracks in the carb and as far as I know the throttle blades were shut.

[TXSTARFIRE]

Correct base gasket? The float position and the needle and seat were a problem but not the cause of your vacuum leak. Should be able to hold the baseplate up to light and with throttle blades closed should see no (or very minimal) light.

[JJDeville]

I took the float and needle and seat out of the rear carb and bent it to match the front carb. I installed a new base gasket and it fired up and seemed to be running good and then it dies and didnt want to crank. I think the rear carb is flooding. Gas is running out of it. The good news is it is not sucking air through the top of the rear carb any more. I think the previous owner may have purposely bent the float to not allow gas to enter the rear carb. I will check it out again later this weekend.

[Kenth]

Make sure you´ve the correct .086" inlet valves in the end carbs.

Also, check the float settings: