Saturday we went on a run with a car club from the Greenwood area. First thing I noticed was the familiar surge at mid teens with light throttle. WAIT A FRIGGING MINUTE! The engine was fine on Friday, now this? I've been down that road before, too many times. I decided to pull the intake manifold and carb as a unit to see If I could find anything wrong.
I'd installed the manifold gasket with RTV and it stuck goood. Destroyed the gasket removing the manifold. But it was evident there had been no vacuum leaks. The vacuum line to the boost/vacuum gauge had been damaged in the engine fire last summer, but on test still held vacuum. The vacuum line to the dizzy was a mess. It is supposed to be rated for fuel and vacuum use, but had malformed and hardened. Looked like it had a couple hundred thousand miles on it instead of two thousand. I don't think it had been holding a vacuum. The PCV line had suffered some fire damage, but appears to be intact. I will have to check it further. It is preformed and will be a hard piece to replace.
Removed the carb, mounting gaskets looked okay. Decided not to trust one of them on reinstall, so made a new one. Removed the jets and idle adjustment screw. The power jet appeared to be not seating , so I installed another one. The car floods and is difficult to start after setting an hour or so, hope that is the problem.
Everything else looked okay, shot compressed air through everything and reassembled. Checked the float level, The damn thing was back to where it had been on two previous occassions! It appears to be made of a mystery metal that creeps back to its previous configuration. But I adjusted the float back to .420", like the book states. Ran a file across the mounting face of the intake to remove some minor burrs it had accumulated over the years. Cut a new manifold gasket, stuck it onto the manifold with RTV, let it set for 4 hours with a flat piece of steel on it to hold it flat, greased the outer face and reinstalled with the carb mounted on the intake.
Being the eternal optimist, I reinstalled the 60 idle jet, thinking I had unwittingly solved the mystery of why the engine needs a huge idle jet. No go. Worked my way back to the 90 idle jet. The engine was now more sensitive to the idle adjustment screw and the idle was much improved. There is now a point at which the idle really falls off and I can actually get a decent idle. Previously, I had to settle for "best rough idle" which is hard to determine.
It was at this time I noticed the gasoline drip into the secondary. I put pressure on the secondary throttle plate, no impact on the drip. That is when I posted about that problem. Jarrids response prompted me to remove the carb, back off the secondary stop, loosen the throttle plate screws and recenter the throttle plate. Reset the stop and reinstalled the carb.
I thought "I've found the problem". "The secondary was not closing, causing a vaccum leak that prompted the use of the 90 jet." So I reinstalled the 70 jet. Ran crappy. Installed the 60. Not much difference. Installed the 90. Once again, that was the ticket. Runs best with idle adjustment backed out about two turns, so its not too big.
Took it out for a trial run. There was a slight surge remaining. How that can be is beyond me. Further checking the secondary found a slight drip that could be stopped with increased pressure on the throttle plate. I decided to use a stiffer return spring, could find nothing appropriate so I cut 4 or 5 coils off of another spring and used that . It appears to have solved the problem.
The carb is now set the same as it was, with the possible exception of the idle speed adjustment screw, but it idles much better.
I was fagged.
Bill
I'd installed the manifold gasket with RTV and it stuck goood. Destroyed the gasket removing the manifold. But it was evident there had been no vacuum leaks. The vacuum line to the boost/vacuum gauge had been damaged in the engine fire last summer, but on test still held vacuum. The vacuum line to the dizzy was a mess. It is supposed to be rated for fuel and vacuum use, but had malformed and hardened. Looked like it had a couple hundred thousand miles on it instead of two thousand. I don't think it had been holding a vacuum. The PCV line had suffered some fire damage, but appears to be intact. I will have to check it further. It is preformed and will be a hard piece to replace.
Removed the carb, mounting gaskets looked okay. Decided not to trust one of them on reinstall, so made a new one. Removed the jets and idle adjustment screw. The power jet appeared to be not seating , so I installed another one. The car floods and is difficult to start after setting an hour or so, hope that is the problem.
Everything else looked okay, shot compressed air through everything and reassembled. Checked the float level, The damn thing was back to where it had been on two previous occassions! It appears to be made of a mystery metal that creeps back to its previous configuration. But I adjusted the float back to .420", like the book states. Ran a file across the mounting face of the intake to remove some minor burrs it had accumulated over the years. Cut a new manifold gasket, stuck it onto the manifold with RTV, let it set for 4 hours with a flat piece of steel on it to hold it flat, greased the outer face and reinstalled with the carb mounted on the intake.
Being the eternal optimist, I reinstalled the 60 idle jet, thinking I had unwittingly solved the mystery of why the engine needs a huge idle jet. No go. Worked my way back to the 90 idle jet. The engine was now more sensitive to the idle adjustment screw and the idle was much improved. There is now a point at which the idle really falls off and I can actually get a decent idle. Previously, I had to settle for "best rough idle" which is hard to determine.
It was at this time I noticed the gasoline drip into the secondary. I put pressure on the secondary throttle plate, no impact on the drip. That is when I posted about that problem. Jarrids response prompted me to remove the carb, back off the secondary stop, loosen the throttle plate screws and recenter the throttle plate. Reset the stop and reinstalled the carb.
I thought "I've found the problem". "The secondary was not closing, causing a vaccum leak that prompted the use of the 90 jet." So I reinstalled the 70 jet. Ran crappy. Installed the 60. Not much difference. Installed the 90. Once again, that was the ticket. Runs best with idle adjustment backed out about two turns, so its not too big.
Took it out for a trial run. There was a slight surge remaining. How that can be is beyond me. Further checking the secondary found a slight drip that could be stopped with increased pressure on the throttle plate. I decided to use a stiffer return spring, could find nothing appropriate so I cut 4 or 5 coils off of another spring and used that . It appears to have solved the problem.
The carb is now set the same as it was, with the possible exception of the idle speed adjustment screw, but it idles much better.
I was fagged.
Bill
