[Kenth]

It´s hard to go wrong with 1/2 - 3/4 turn preload on the air
valve spring with the DA rods.

It´s not uncommon to find the secondary POE tubes loosen from the airhorn ending up in the secondary POE wells.
Also the small holes from the float bowl to the secondary POE wells may be obstructed so fuel wont reach the wells.
Sometimes it may be beneficial to open the secondary POE outlets from .063" to .078" which is used in many High performance Pontiac Q-jets.

This assumes, good cylinder compression, a proper functional ignition centrifugal advance and correct voltage to the ignition coil for the ignition system used.

[abefromen]

Originally Posted by "QUICK-SILVER"

Is the cam that works the secondary hanger/metering rods moving the hanger up when you open the air valve? Seen a few of them gone/broke and it cause the problems you're having. And easily overlooked unless you're checking for proper metering rod lift.

It's new.

Originally Posted by "QUICK-SILVER"

And hope you don't have a fuel pump eccentric problem like Sam had in the timing chain thread.

Quadruple checked when I installed the cam sprocket.

Originally Posted by "QUICK-SILVER"

May end up having to add your electric pump in back for a pusher.
Clay

Cant imagine that'd be necessary in such a low po application. Engine hasn't yet nor will it ever see anything much north of 4000 RPM.

[abefromen]

Originally Posted by Kenth

It´s hard to go wrong with 1/2 - 3/4 turn preload on the air
valve spring with the DA rods.

It´s not uncommon to find the secondary POE tubes loosen from the airhorn ending up in the secondary POE wells.
Also the small holes from the float bowl to the secondary POE wells may be obstructed so fuel wont reach the wells.
Sometimes it may be beneficial to open the secondary POE outlets from .063" to .078" which is used in many High performance Pontiac Q-jets.

This assumes, good cylinder compression, a proper functional ignition centrifugal advance and correct voltage to the ignition coil for the ignition system used.

My bad on stating earlier that the carb had a POE system....It doesn't have six tubes in the airhorn so I guess it doesn't have it. It's also APT equipped.


Pulled the carb off the engine and opened it up to get a much better look at things. Its as clean as can be inside with no crud in the float bowl and no plugged tubes or passages.

What I was able to do was take a much more accurate reading of the float level and found it way lower than 1/4"..........more like 10/32". I'm going to raise it up where it should be and try it again.

Hoping it's that simple of a fix because it feels like classic fuel starvation to me. If not I'll have to take a look elsewhere.

[abefromen]

Originally Posted by PontGuy

Surprised that you would have a huge bog problem with a Cliff-built carb though. The two that I got from him were tuned perfectly right out of the box.

Ditto on two others he has built for me in the past.

That's why I'm leaning towards something other than a carb issue as the only thing I found today upon closer inspection was the float level under 1/4"....

[Kenth]

Originally Posted by abefromen

My bad on stating earlier that the carb had a POE system....It doesn't have six tubes in the airhorn so I guess it doesn't have it. It's also APT equipped.


Pulled the carb off the engine and opened it up to get a much better look at things. Its as clean as can be inside with no crud in the float bowl and no plugged tubes or passages.

What I was able to do was take a much more accurate reading of the float level and found it way lower than 1/4"..........more like 10/32". I'm going to raise it up where it should be and try it again.

Hoping it's that simple of a fix because it feels like classic fuel starvation to me. If not I'll have to take a look elsewhere.

I´m familiar with your Q-jet, and i´m talking about the SECONDARY POE system.
Some name this the secondary accelerator ("pump")-shot.
This feature pulls fuel from the secondary wells and discharges fuel just in front of the airvalves when they opens.
Only some marine and some early CBB Q-jets lacks this system.
Hope this makes sence....

And, hold the airvalves closed, turn the setscrew so the spring hook just touches the pin, then turn 1/2 to 3/4 more for initial testing.

[77 TRASHCAN]

My thinking is to get a couple of cans of spray carb cleaner, hit all the passages, blow out with air, repeat, reassemble, see what happens..

[Gary H]

Does the engine have this problem when it is cold too? If so, that probably eliminates vapor lock. Still could be fuel starvation though. May have to add an electric pusher pump.

[abefromen]

Originally Posted by Gary H

Does the engine have this problem when it is cold too? If so, that probably eliminates vapor lock. Still could be fuel starvation though. May have to add an electric pusher pump.

Yes.

Cant imagine this stock application needing a pusher pump.......250 Hp at best low RPM cruiser. Something isnt right.

Idle, off idle and mid range cruise are perfect. Once I get on it and into the secondaries it falls flat. Not too bad at higher RPM cruising speed but at lower RPM under load its horrible.

[abefromen]

Raised the float level up to 1/4'.......Made no difference. Prob still there.

Could this be ignition related? Stock HEI rebuilt/recurved and added a NOS module and new coil.

Grasping at straws now

[PontGuy]

I've been hesitating to throw this in the mix, but since its gotten to "grasping" at straws...

The last Q-jet I had that didn't want to "take" the secondaries was just a junk spare that I used for a new engine build until I got my Clif-built carb. I worked out the bog by restricting the pulloff vacuum, cutting some little slots at the POE outlets per Clif's book (I think your carb already has slots) and by quickening the distributor curve. I really think that the lazy mech advance curve that I started with had a whole lot to do with it. The carb worked pretty good on the engine after that.

What does your timing curve look like and are you sure that the distributor is advancing properly?

[77 TRASHCAN]

Do not cut the slots on the air flaps on this specific carb. They do not need slots and are in perfect position under flaps and actually have a small opening cast into the casting leading to the orifices, AND the tops of the openings protrude slightly above the air flap when it s closed! This carb needs NO help in this area. Might check to make sure tubes are not crammed too tight in casting, restricting or stopping flow of fuel...

[abefromen]

I will have to find the dizzy spec sheet.

No slots in the secondary air valves.

Thing is, the prob isnt just a momentarily bog/hesitation then it takes off.......its a complete fall down to where its sputtering and really holds back like it starving...or maybe an ignition issue under heavy load?...just totally falls down. But if im going 50 and push down the gas relatively quick 9 times outta 10 it will downshift and take off with secondarys wide open and howling.

[74Grandville]

I have seen a similar situation on a carb that dropped one of the secondary POE tubes. It sounds like you have opened the carb though to adjust the float, so I would have thought you'd see the tube in the well vs installed in the top.


Sent from my iPhone using Tapatalk

[PontGuy]

Just to be clear I was not suggesting that you cut slots on a good Clif-built carb. Mine was just a temporary cheap Chevy carb that I had kicking around, so nothing to lose. Just relating the things I did that got the bog resolved, and recommending that you make sure that your distributor advance is working right and not too lazy. In my case I think that was the biggest part of the problem.

The bog was similar to what you describe. It wouldn't always "take" the secondaries at all. But when it did the car would really go.

[Kenth]

Do the HEI get full voltage or do you use the original points ignition harness w/reduced voltage/amps?
The HEI needs a dedicated full power source.

[abefromen]

Originally Posted by Kenth

Do the HEI get full voltage or do you use the original points ignition harness w/reduced voltage/amps?
The HEI needs a dedicated full power source.

Full 12V directly from the ignition switch.

[Cliff R]

What intake manifold?

Spacer?

What air cleaner assembly?

Do NOT modify the POE system, flaps, or anything else on that carburetor, it doesn't need it.

May just have to install a slower pull-off to delay the opening rate of the air flaps, if there isn't anything else going on that is contributing to the issue......Cliff

[abefromen]

Originally Posted by Cliff R

What intake manifold?

Spacer?

What air cleaner assembly?

Do NOT modify the POE system, flaps, or anything else on that carburetor, it doesn't need it.

May just have to install a slower pull-off to delay the opening rate of the air flaps, if there isn't anything else going on that is contributing to the issue......Cliff

Edelbrock Performer

No spacer

14" diameter open element air cleaner with a 3" tall filter.

[Greg Reid]

I know you said it was new but take a close look at that secondary metering rod cam. I had one that behaved just like you describe and that plastic cam was cracked. The valves opened but the rod did not raise to allow enough fuel in the secondary. It would fall on it's face immediately when I floored it. The cam looked like it was in one piece when at rest.

[Kenth]

Originally Posted by abefromen

Full 12V directly from the ignition switch.

Original HEI equipped or modified harness points-equipped car?