volition

I just finished putting this thing back together and apparently I messed up somewhere.

It's idling at about 1500-1700 rpm and fast idle is 3500 rpm!

Everything is unplugged and vacuum ports are ALL capped. The only thing hooked up is the PCV hose.

The idle mixture screws are about 1 turn out and the idle speed screw is backed all the way out to where the throttle isn't even touching it anymore.

The only thing I can think of that would cause this is when I was putting the baseplate back together I could see light around the throttle blades on both the primary and secondaries. A very miniscule amount of light on maybe 1/4th as this seemed to be the best fit I could achieve.

Now if I set the choke to be closed it will idle really low, like 500 rpm and very badly.

But as soon as the choke opens when the car is warm its back to 1500rpm idle and the idle screws do nothing.

Would it be causing this?

Any other ideas on what to start looking for?

myk7

My guess would be that you don't have all the choke stuff installed correctly, keeping the throttle linkage from returning all the way... or a massive vacuum leak. Can you post a pick of the choke levers and such?

volition

I thought that at first too .. I took a peek down the barrels during operation.

In the chokes fast idle position it's holding throttle about 1/4 open. In normal idle when I disconnect the choke linkage and the throttle blades close they close fully but idle is still 1500+ RPM

Im starting to lean towards a massive vacuum leak but not sure where. I have everything capped including the choke pulloff and the choke itself.

I used a new base gasket that's 1/4 inch thick as well.

myk7

Checked the intake for hoses that may have fallen off? Brake booster hooked up? Maybe hook a vac gauge up and see what it's reading?

volition

Running with the air cleaner off while adjusting. Booster is hooked up directly to manifold (I'm trying to undo years worth of Bubba work, haven't got to that yet) which is an Edelbrock non-egr Performer.

Vacuum is reading 21" at the 1500 rpm I can get it to. If I could get it to idle any lower I could tell you what it is at idle

Could this non-egr Manifold be somehow causing a vacuum leak because this Quadrajet does have EGR passages?

myk7

I wouldn't think so, not if you have everything blocked off. Was this setup running "ok" before the carb rebuild? The intake is a spreadbore intake?

volition

It's a combination spread/square bore intake.

I had an Edelbrock on there before.

The gasket seems to cover all of the necessary areas to make a seal except the middle which shouldnt be leaking vacuum anyway

myk7

I don't really know what else to tell you. Unless you have the vac advance hooked up to manifold vac when you previously had it hooked up to ported vacuum, but you should still be able to idle it down I would think. Sorry... maybe somebody else has some ideas?

Jeff_Keryk

Turn the idle speed screw all the way out so the throttle blades close. If the engine will not idle down and die you have a vacuum leak, because air must be getting in somewhere. If your throttle blades will not close, they are obstructed somehow.

volition

It does seem to be a vacuum leak.

When I spray carb cleaner near the choke against the body the idle goes up even more.

I've converted to an electric choke anyway.. how do I seal off the choke? As I recall there was one vacuum orifice that comes straight out of the carb body and hooks to the housing.

It's also possible it may be leaking at the baseplate to bowl gasket but i figure ill start with the choke first.

Any suggestions on plugging the thing up?

Jeff_Keryk

From Cliff:
http://www.cliffshighperformance.com...lectric_1.html

...Roger...

Have you determined the throttle plates are in fact closing ?
From your OP it sounds as if they are not , did you remove the plates from the shafts ? If you did remove them you must seat them so they close completely.

Beyond that there are many things that can cause vac leaks,one is the gasket between the center and base,you must match it,I've seen plenty that are close but not right.Some of these new kits don't have the correct gaskets.

jimboscarbs

If you used the wrong screw (one out of the top) when putting the base plate back on, the screw bottomed out before the base plate tightened against the center section of the carburetor. This is an easy mistake to make, not all of the screws are the same length. Also if there is one in the direct center of the base plate when you flip the carb over ( not all carbs have this) take that screw out and leave it out or else it will end up stuck in the top of a piston. Also if you pulled the butterflies out of the secondaries be very careful when you drive the car because the secondaries will stick open far enough to run the engine at 3500 RPM ( This doesn't take much). It is no easy feat getting the butterflies back in right if you have never done it before.