Hi . I have not been driving my 68 Ninety Eight Convertible for couple years because of health , I was keeping it started BUT about year ago I couldn't get started , SO last month I changed fuel pump cause it was not pumping fuel to Carb , Changed the Carb with another off a 455 that was rebuilt about 10 years ago , still no run . checked coil , it was bad changed that , Fired right up but now is running hot , Intake in middle of both banks hot enough to scorch the paint . after running for several miniutes ,when shut off it DEISELED and would not stop , when it did it coughed back thru carb / ????? When I was driving it a lot most everything was OK , DRIVER bank did run a little hot . Carb settings at 2 1/2 turns out .
ANY HELP FOR AN OLD MAN Thanks in advance .
rocwal
Dan B

 

Leave the new coil in there, but switch back to the old carb and see if it runs ok.

 

That is where the exhaust crossover ports are, so there is normally 1000+ degree exhaust gases flowing there and the paint will not survive. But I'm guessing from your post that this is something new, so as said above, it may be the engine is running lean due to the carb swap, or another idea there may be a vacuum leak that's causing a lean condition.

 

Dan,
The timing could be retarded or carb A/F adjustments could be lean or you have a vacuum leak or all the above.
The replacement carb may have the wrong base gasket or wrong rods n jets, hanger, and AV cam for your application(too lean).
Run-on (dieseling) is caused by a few things...some of which are curb idle RPM setting too high, timing wrong, excessive cylinder carbon build-up, wrong plugs et al...

1. check for vacuum leaks.

2 Verify and adjust ignition timing as needed, Try 10-12* base timing (vac advance disconnected and its source plugged).
Give as much timing as it will tolerate without spark knock under hot load.

3. Points ignition? Verify the points are good and the dwell angle is 30* (~.016" on a grease-free feeler gauge).

4. Verify the vac advance is working. Total timing with it working is about 20-22* at curb idle...so 12* base and the can brings in another 8-10*.

5. Adjust the A/F ratio on the carb to achieve the highest possible vac reading at curb idle with a vac gauge.

6. Go back n forth between timing and A/F ratio to achieve the highest vac reading on said gauge.

7. Road test and repeat until its where you want it.


As a general suggestion/permanent solution for the burnt intake is to plug off those crossover ports in the intake, remove the thermo stove flap in the drivers side exhaust manifold, weld the shaft holes up then install an electric choke and be done with the heat.

Fun I type slower than you...

 

A 1968 has a heat riser valve in the driver side exhaust manifold outlet port. If the car hasn't been run in a while, chances are the valve has rusted shut. Now all the exhaust runs through the heat crossover under the carb. That will explain both your excessively hot intake and your other problems.

 

Good catch Joe.
Forgot about that one.
Had a 70 small block vette that did this. Removed frozen valve, welded the shaft holes, welded the plugs into the intake vs heads.... problem solved and freed up a tiny bit of exhaust flow(extrude honed as well).

 

Thank 's to all , I have a person that is going to check it as all of you stated . First I'm going to change back to original Carb . There is no heat damper on Driver side , it has factory replacement Duels , Thorton's Driver side Manifold .

Dan B