Quadrajet Problem Solving > Dialing in your rebuilt Quadrajet carburetor

7029207 transition too rich

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bob69:
Cliff, forgot to mention the power piston. Holley did cut the pin on the power piston. It was tossed and replaced with one that has the pin. I've collected several PP over the years. Most have the same height from the end of the pin to the top of the hanger. I used one of these.

I'll consider upgrading to an APT, but the last time I tried to remove the stock screw it would not come out. Buggered it up pretty good.
 
The Holley PP spring looked too long. It was replaced with one from a 7029207 carb. After all of the other changes were made, i'm seeing a sharp lean condition (afrs in the 17 range) at 1800 to 2000 rpm on wot. Power drops momentary then picks up. I suspect the PP spring is too weak. Would a weak PP spring cause the this condition. 


Also not mentioned. Holley put inserts in the MABs and LIAB. The UIAB was not molested. I do not know what the air bleeds should be on the stock carb. So I was not concerned with drilling them to a larger size.

Cliff Ruggles:
APT is a nice feature on those units.  Remove the cover, use some penetrating oil and heat from underneath with a propane torque.  99 percent of the time they will come right out.  If you try to remove them before they are ready it usually results in breaking or mangling the screw.

I make a external APT screw with a spring on it so it holds it's adjustment. 

Since you are tuning with a wide-ban you need this feature.  Otherwise you are having to remove the top and change metering rods when all you had to do was keep the same metering rods and raise/lower it to get where you need to be.

In all the years I've been doing this I've found four defective castings.  Two were 1971 Pontiac 7041262 Pontiac units.  The other two were Edelbrock 1905 and a 1910.  They had leaks between the main bowl and the passage under the DCR's.

I've rebuilt/restored hundreds of 7029207's and haven't ran into a defective one to date.

The lower IAB's are small and the uppers are larger for the originals and SR's.  I've observed several different size idle tubes used in them and different jet/rod combinations.  The originals that I've seen were a tad leaner for jets/rods on the primary side.  I don't think any of them were altered prior to taking them in, but you never know with these things as they have been out there for half a century at this point......

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