ok just got it on today and autozone sales a sweet rebuilt carb for $148 i didnt even have to tune it but with the new carb it fixed eveything eles but it still is doing a engine run on so i think it has alot of carbon build up on the pistons but here is a video
http://media.putfile.com/1969-Cadillac-Eldorado-500-Big-Block-new-carb

but what should i do about the engine run on?

Some cars use a solenoid for idle setting. Did your old one have one?

You're probably right about the dieseling (run on) being caused by carbon buildup. I used the method detailed a lot here with GM Top Engine Cleaner - hold the engine RPM at 2000 or so and spray the can into your carb, kill the engine when you see lots of white smoke coming out of the exhaust, and let it sit for a while (preferably overnight).

My dieseling was actually caused by the carb itself, however. When I adjusted the fast idle and choke to the factory specs, it stopped. Also, your '69 has a high compression engine, which can diesel if you're using low octane gas.

You're probably right about the dieseling (run on) being caused by carbon buildup. I used the method detailed a lot here with GM Top Engine Cleaner - hold the engine RPM at 2000 or so and spray the can into your carb, kill the engine when you see lots of white smoke coming out of the exhaust, and let it sit for a while (preferably overnight).

My dieseling was actually caused by the carb itself, however. When I adjusted the fast idle and choke to the factory specs, it stopped. Also, your '69 has a high compression engine, which can diesel if you're using low octane gas.
i got like 91 octane in it rite now and that GM top engine cleaner will that hurt my motor the motor has 80k on it or 108k idk somewhere in there so will it like mess up a piston or something

I had 105K on my engine when I did it with no problems. I don't see how it could mess anything up and have never heard of it, so I would say you're okay. If you're still concerned about the Top Engine Cleaner, there's a product called SeaFoam that doesn't have as many chemicals in it that you could try first.

Go ahead and use the TEC. Everything important in your motor is metal anyway, there's not a big chance you'll mess anything up.

I am having the same problems with dieseling, I originally thought maybe my carb just needed a rebuild, although a 94,000 mile motor from 1970 ought to have some carbon deposits. I want to use seafoam or TEC to get those deposits out. I asked my dad about it and he said sometimes stuff like that actually increases oil consumption and causes it to run worse because sometimes the carbon deposits are helping seat the rings and valves. He said it might be a good idea but it depends. Can this actually be detrimental? I know I have a bad dieseling problem thats for sure. I am running 92 octane on 10:1 by the way.

I am having the same problems with dieseling, I originally thought maybe my carb just needed a rebuild, although a 94,000 mile motor from 1970 ought to have some carbon deposits. I want to use seafoam or TEC to get those deposits out. I asked my dad about it and he said sometimes stuff like that actually increases oil consumption and causes it to run worse because sometimes the carbon deposits are helping seat the rings and valves. He said it might be a good idea but it depends. Can this actually be detrimental? I know I have a bad dieseling problem thats for sure. I am running 92 octane on 10:1 by the way.
ok how do u get your car to to turn off when its dieseling i have to go put something over the carb for it to stall then it back fires up out of the carb with alot of black sh*t and i dont like doing that so how do u turn the car off when dieseling

Since it started dieselling I have always just shut the car off in Drive, and then put it in Park once the engine is off. 90% of the time it will want to diesel, but can't, 10% of the time it gets an extra crank out. If I shut it off in park it cranks over about 5-10 more times before it finally sputters out. It's really only a temporary solution as im sure its still bad for the engine, just not as bad as letting it diesel for 10 cycles.

if my carb is not tuned the rite way could it make it do a engine run on?

Yeah it could I believe, for one, If your idle is set too high it will run-on. Also I don't know if your carb has it or not but sometimes theres a solonoid that shuts the intake or something, keeping fuel vapour from entering the engine after it's shut down.

Yeah it could I believe, for one, If your idle is set too high it will run-on. Also I don't know if your carb has it or not but sometimes theres a solonoid that shuts the intake or something, keeping fuel vapour from entering the engine after it's shut down.
yea i need to fix the idle idk why its so high and to let u know that seafoam worked really well i dont got a run on anymore

I asked my dad about it and he said sometimes stuff like that actually increases oil consumption and causes it to run worse because sometimes the carbon deposits are helping seat the rings and valves. He said it might be a good idea but it depends. Can this actually be detrimental? I know I have a bad dieseling problem thats for sure. I am running 92 octane on 10:1 by the way.

Carbon on the rings will cause them to stick and quit moving, thus quit sealing as well as they should. Northstar owners are always told to do wide open throttle runs to excecise the rings and keep carbon off them. Carbon on the valves will reduce airflow, and can cause hard starts as it soaks up gas (on the intake valves.) These types of chemicals can be detrimental in other ways but not how your dad is saying.

Awesome, I'll put some seafoam in in a few days then, I'd say its worth a shot.