I need a good and fair priced mechanic in the puget sound area, preferably on the Eastside.

My newly installed Super Six will not idle!! runs like a top on the road, but dies when it drops below about 1200 rpm I have rebuilt the carb, set the timing, checked every vacuum line. and cursed at it repetitively.

I think i need to hand it of to someone with better diagnostic tools.

Any recommendations?

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My 68 Dart GT 225

I would re-check the carb rebuild because it sure sounds like a vacuum leak. Can you hear any whistling from the carb?

I know a good independent garage in Buckley, but that's a long haul for you.

Can you find another carb to swap?

The carb on it now is a carter 2B. I have a Holley 2B that was removed from a running sl6, and it had the same problem when I put it on last night.
I added a thin layer of seal on the gasket, and made sure it was bolted on tight.
could it be Manifold leak?

Strange thing is, it was Idling before i rebuilt it, but it was very hard to start cold. choke would not open. I found a bolt laying on the manifold, under the choke thermo cover, and i think it was binding the spring.
it is electric assist, but it is not plugged in, seems to choke fine now without it.

the Carters are sort of tricky to rebuild because of the pump arm adjustments, but I set them according to spec. The only thing I'm not positive about is the float adj. I left this alone, but I 'm not sure that would be the cause of my problem.

I noticed that when it idled before, the pump arm was actually out of whack, to the point that it lifted the dust cover when the engine wasn't running,

The fact it does this with two different carburetors points us elsewhere in the system.

If it were a manifold vacuum leak large enough to prevent the engine running at all below 1.2 KRPM, it would almost certainly run very rough above that speed.

I would look closely at the EGR system, whether you are actually using it or not. If the EGR valve is partially or fully open when it should not be, then the engine will refuse to run below about 1.2 KRPM.

EGR valves can be open when they shouldn't be for three reasons:

1) Valve OK, passages clean, EGR control system improperly hooked up. There is a vacuum network that controls when the EGR valve opens and closes. It's supposed to remain closed at all engine speeds before the engine reaches a specified temperature, and it should never be open at idle or low, steady engine speeds. If vacuum is reaching the valve under these conditions, then it is because something is faulty or hooked up incorrectly in the control system. Test by removing the hose from the EGR valve. If the engine suddenly runs below 1200 RPM, you've found the problem.

2) Valve OK, control system OK, passages clogged with carbon. This can prevent the valve from seating all the way in the closed position. It allows exhaust to enter the intake tract even when there's no vacuum to the valve. Usually best to replace the valve and clean out the passages in the manifold.

3) Control system OK, passages clean, valve shot. Sometimes the return spring fails, allowing the valve to remain open all the time. Sometimes the valve plunger gets burned so it doesn't seat correctly.

Or perhaps you're not running an EGR valve at all, but instead have a blockoff plate. If the plate is worn or the correct gasket isn't used, you will get constant EGR, and it can be of high enough volume to cause low-speed running problems.

Another "gotchya" is cracks or holes in the floor of the intake manifold. This is not incredibly common (but not unknown) with the iron manifolds, and VERY common with the aluminum manifolds. If you're running one of those aluminum 2bbl intakes that has a very distinct weld bead around the whole perimeter at the top of each runner (looks like a manifold with a manifold-shaped plate welded on top), throw it in the trash and get an iron one. The aluminum Mopar Performance manifold doesn't have the problems the factory casting did.

DS

Picked up a new Carter 2b @ Napa. Runs like a dream!!

Varnish buildup.....That's why the rebuild didn't help.

thanks all.

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My 68 Dart GT 225