I cranked up the Turbo Dart today. The engine wouldn't idle, so it often took a bit of pumping the accelerator and holding the revs over 1,000 RPM. It still would often start to die on me if I held the accelerator steady, and it belched clouds of acrid smoke like it was running very rich. It also turned out the oil drain back line was leaking.

I did notice there was a vacuum leak on it (a port in a weird spot on the manifold under the carb hadn't been plugged) but I'm not sure why it was running so rich. The vacuum gauge showed fairly low vacuum, like around 8 inches of mercury, at idle. Maybe it was running rich because I was pumping the accelerator to compensate for a tendancy to lean out? Maybe the thing's flooding on me again with a stuck needle valve? I'll have to take a closer look at it next time. Any thoughts? The carb is a 390 cfm mechanical secondary Holley with no choke.

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"Mad Scientist" Matt Cramer
'66 Dart - turbocharged 225
My blog - Mad Scientist Matt's Lair

What number power valve is in the carb?

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Official Cookie and Mater Tormentor.

Make sure the o-rings around the needle valve are not all dried-out or broken.
Triple check for vacuum leaks, it will not idle with a vacuum leak.
DD

I second the good Doctor. Classic signs of a vacuum leak.

Reed

If all that checks out, take a look at the distributor. I've had one where the advance mechanism was broken, and was retarding timing as RPMs increased.

Wouldn't idle, and belched out clouds of black smoke from the fuel it couldn't burn. Would momentarily run OK, then start to die as the timing wandered around.

Just take the cap off and give the rotor a snap against the springs. Should snap back smartly with no extra movement. Or shoot a timing light at it.

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It's a Slant thing. Even I don't understand.

1974 Duster, EFI /6 soon to be turbo...

Get that Monkay! Get that nasty thing!!

Thanks for mentioning the needle valves, Doc - I had a problem with the rear one freezing completely open a while ago, sprayed it with carb cleaner and that seemed to fix it but maybe I ought to replace some of the parts there. I think I got the vacuum leak but haven't had the chance to start it since I took the oil return line apart.

Slantzilla, I bought the carb used and do not know what sort of power valve it has. BTW, this is set up as a blow through.

GunPilot, the engine was working OK before I started the turbo conversion. Interesting problem, though, maybe I should make sure the spark is working consistantly.

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"Mad Scientist" Matt Cramer
'66 Dart - turbocharged 225
My blog - Mad Scientist Matt's Lair

Do you have the turbo blowing thru the carb? Does it run correctly without the turbo blowing thru the carb?

I founds some pics I took of the problem I am talking about.

This is how the advance arm/shaft shouldbe aligned. I made a mark (arrow) showing proper alignment.



This shows how the pieces could move.



This was my solution.




This problem was good for about 20 degrees of timing loss off idle with symptoms you describe including low vaccum. Just a thought.

Might make sure the power valve isn't blown too.

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It's a Slant thing. Even I don't understand.

1974 Duster, EFI /6 soon to be turbo...

Get that Monkay! Get that nasty thing!!