Engine will not idle down

[hoover]

I built a 505 with stealth heads using a cast iron dual quad manifold from tthe early 60s. On top I have a pair of edelbrock afbs.
The problem I am having is that it will not adjust down to a reasonable idle rpm unless the timing is really retarded.
The idle speed screws are backed out so they are not even touching the stops.
Throttle cable and kickdown linkage are disconnected.
It will not idle below 2000 rpm unless i twist the distributor until it barely runs, then i can only get it down to 1000 rpm.
I've been through the carbs several times. When spraying flammable aerosol around the carbs there seems to be no fluctuation.
Any ideas?

 

[turbine68rt]

Make absolutely sure that one or both of your secondaries are fully closed at idle.

 

[eldubb440]

electric choke? no choke? are you on the choke idle adjustment?

 

[khryslerkid]

Check for a vacuum leak. Manifold gasket, vacuum port on the manifold ect.

 

[hoover]

All of the throttle blades are closed tight.
There is currently no choke, or choke linkage on either carburetor.

I sprayed ether around the top of the intake, but it didn't seem too effect the engine speed.

 

[AR67GTX]

If the throttle blades are closed tight and you are not finding an external vacuum leak, it’s getting air from somewhere. If it wasn’t a Mopar I would suggest the possibility of an internal intake gasket leak, pulling air from the crankcase. But the typical B/RB valley pan pretty much eliminates that. Got to be a pretty good leak to idle at 2000 rpm.

Power brakes? If so might try plugging the vacuum hose off for a test.

 

[SlinktRR]

Almost guaranteed intake manifold leak. I would remove and reinstall. Pay close attention to sealing around the intake ports. I've had high idle before and it was an intake port leak, pulling air and some oil from the crankcase like AR67 suggested. You won't detect that by spraying carb cleaner.

 

[R413]

Classic vacuum leak. Figure it out, it's there.

Or the carburetor is bad, try a different one, or this carb on a good running engine.

 

[Geoff 2]

The factory intake probably used the inner set of mounting holes on the E carbs. Very possible that the carb flange on the intake are not sealing the passages in the base of the E carbs. I understand E male a thin spacer plate to go under the carb to seal up the passages.

 

[hoover]

Thanks for the advice.
No power brakes.
The intake will be coming off tonight.
I will report back

 

[Mick56]

A smoke machine is a good way to find leaks

 

[hoover]

Is that something you would make?

 

[RemCharger]

Pack a Marlboros and a vacuum hose?

 

[hofferwood]

ford escort I had

 

[AR67GTX]

If the throttle blades are closed tight and you are not finding an external vacuum leak, it’s getting air from somewhere. If it wasn’t a Mopar I would suggest the possibility of an internal intake gasket leak, pulling air from the crankcase. But the typical B/RB valley pan pretty much eliminates that. Got to be a pretty good leak to idle at 2000 rpm.

Power brakes? If so might try plugging the vacuum hose off for a test.

Actually, via brain fart, I was discounting on a B or RB engine, a leak from the crankcase due to the valley pan - until it dawned on me that the valley pan is the intake gasket. Been too long and too many Chevy engines since I’ve had mine off I guess. That actually is a good possibility for an air leak into your intake/cylinders. Hard to diagnosis without pulling the intake. But an oily plug or if you have an endoscope inspection camera you can remove the carb and go down the runners to look for oil in the intake and on top the intake valves. If you find that, you probably need a new intake/valley gasket. Here is a good video on how to install an intake and prevent a vacuum leak.

 

[WileERobby]

And your vacuum gauge readings are .................... ?

 

[hoover]

18 in

 

[66 Sat]

Dumb question, but there aren't any air bypass holes drilled in the throttle blades?
What's the history on the carburetors?

 

[hoover]

No holes.
I took both carbs apart and had them vapor blasted.
Both got edelbrock kits .
I have been through them both multiple times looking for problems and can't find anything

 

[hoover]

I removed the intake manifold.

When sitting back on the engine with no gasket a ..018" feeler guage will slide in between the head and maifold in the right rear corner.
I checked all around with a .005" and that did not go in anywhere else.
The gasket mating surface in that area shows more of a witness mark from the gasket than the other three pairs of holes.
In the past I have only used the valley pan. This time when i put it together paper gaskets were included so i thought why not?
What do you guys do?