Just replaced my stock Quadrajet manifold with an Edelbrock Performer that was drilled for a PCV and oil fill tube.
Before tear down, the engine ran great, idled great. I painstakingly made sure the FelPro gaskets from Edelbrock was installed correctly, followed John's intake manifold procedure, retimed it to 8 deg., same carb, didn't touch any settings. Had trouble starting it and once started, difficult to keep running. Will not idle!
What is wrong? Is the manifold leaking? What do I check?

 

If you followed JohnZ's procedures it shouldn't have required retiming; unless you messed with the distributor indexing or cranked the motor. Start there...make sure you aren't a tooth off and the plug wires are in the correct order....

If stock, thing should look like this:

 

Agree the most likely culprit is the timing...

 

Sounds like a Plug Wiring or Timing issue. A Vaccuum Leak could also be involved. Stuck Float in Carb? Is the Carb to Manifold Gasket installed correctly and not 180* out? Al W.

 

For sure timing and plug wiring, but you said you changed no settings on the carb? That new manifold has completely different flow dynamics than the stock or original one does, or any other one for that matter.

I really can't believe it would run with the same quality as the original ran with out making fuel air mixture adjustments.

 

I stabbed the distributor 47 times today and pretty sure it was right 46 times. I have it timed to 8 deg. (hard to tell at fast idle!), but I'm sure it's not timing. Also, the wires were never removed from the cap or plugs. Carb gasket correctly orientated.
I thought the carb should act the same as it did on the old manifold, maybe I was wrong. The problem is the idle mixture screws on the carb are frozen.
I will attempt to unfreeze them if I knew that they had to be readjusted after changing manifolds. Anyone have an opinion or experience on this?

 

a pcv creates a controlled vacuum leak, a needs to be carefully calibrated. a very lean mixture could have those symptoms

 

Calibrated meaning the idle mixture screws need adjustment? I know i am running lean.

 

plug the pcv and give it a try, it will richen it up, pcv carbs and normal have different jetting

 

Never heard of such a thing - what do you mean, they're "frozen"?

 

Emission idle mixture caps??? Who would reinstall them?

 

From your description I would lean, no pun intended, toward a vacuum leak.
With the engine running a low as you can keep it running, slowly close the choke blade little by little, if the engine RPM increases a lot then you have a lean condition, more than likely caused by a vacuum leak.
Are you running a Qjet, Holley or a Carter?
Joe

 

Frozen, as in extensive corrosion of dissimilar metals. I started soaking them periodically in PBS Blaster about 6 months ago. Yesterday I added acetone & transmission fluid. This morning the heads twisted off. Scrapped carb!
Installed a new kit in another carb today and will try it tomorrow.

 

You gonna push that thing to the cruise in on Friday???

 

Qjet. Thanks for the tip, I'll try it. Sounds like you all are right, I think the "vacuum leak" is caused by the PCV valve. Just don't know what to do about it.

 

Bring a tow strap!

 

Get a spray bottle , fill it with water and a little bit of dish soap (not the stuff you put in dish washers).

Start the engine, get it running on it's own, then spray the water soap mixture all around the base of the carburetor, where it mounts to the manifold. Look for bubbles.

Spray the PVC area, and also the intake mounting area at the cylinder heads.

Look for bubbles = vacuum leak.

I had a similar problem when putting a freshly rebuild 56 Rochester 4GC on my 56. The soapy water confirmed a vacuum leak at the base of the carburetor. Turned out this professionally rebuilt carb had a warped base plate.

Took a base plate off another 56 4GC and that fixed most of the problems.

 

Appreciate the tip but doesn't sound logical. Air is sucking in on a vacuum, not pushing air out. Am I missing something?
I remember my dad had a oil can filled with transmission fluid and he would squirt oil at the edge of the intake while the engine was running. When there was noticeable smooth out of engine rpm, and he could see where the oil was being sucked in, there was the leak. Hate the thought of doing that on my new Edelbrock alum. Manifold!

 

An unlit propane torch pointed at likely areas will find the leak. If the idle smooths out when propane is sucked in -- there's your leak.

 

Sorry to read the news 59 as i know u really put some time and effort getting that intake ready. Well the timing light doesnt lie. If u have 8* initial using the timing light its ast 8* adv then initial timing is not bad. That doesnt rule out if the dist decided to quit - it can happen. But easy to test again with your timing light and u can watch timing as u increase rpm (no need to go above 3,000rpm) and see it adv increases to near 30*.

Next, sometimes the carb bowls dry out when not used and leaves fuel tar residue in the tiny passages. Not an easy fix. Or sometimes just the float will stick or the needle inlet vlv will get stuck and sometimes a good shake will loosen it up for use.

Yes vacuum leak possible but usually that makes the engine burn oil or at least oil consumption goes way up to like a quart every 1,000mi. Also sometimes bad gasket seal will leak water into the crankcase and u should look at the oil for water contamination.

So now the idle screws are still frozen with the screw heads sheared off? But unless u changed something else on the carb it should still have the stock tune and usable for trouble shooting. I hate to see u get fixed on a carb issue when the original maybe still useable for trouble shooting this hard starting and rough running.
BTW did u remember u needed a divorced choke adapter? Is the choke working properly? Does it close cold and gradually open as the engine warms up - to fully open?
Just my 2 cents but i would take that original carb and give it a good shake then install it to watch and verify proper choke operation.

That enough for now and let us know what u find.