WOT A/F tuning question 73 455 Pontiac carb

[jlutz455]

I had my 73 455 Pontiac carb. dialed in nice, but once hooking up a wideband, found it to be a little rich across the board ( 11.2 idle, and cruise A/F).  I put back the stock 71 jets and primary 44 rods and now idle and cruise A/F are great at 14.1 and 13.5 respectively.   

The only challenge is WOT.  The airdoor opens with no bog or lag.  I have a " G" hanger, but whether I use my AV or CE secondary rods, the WOT A/F is  9.5-10.    Almost feel like I need a custom primary rod with a 0.036" power tip instead of stock 0.026" tip.  Any other ideas ?  Thanks!

[Cliff Ruggles]

Need a bit more information.

What is the carburetor part number?

What size are the main airbleeds in the airhorn?

Does the carb have primary POE?

Have you made any adjustments to the upper MAB screw in the airhorn?

What else has been done to the carb, rebuilt, fuel inlet seat diameter, float setting, etc?.......Cliff

[jlutz455]

Carb is pn 7043263 (actually a 73 400 MT carb).

I wrote all my #'s for the air bleed sizes in your book so I'll check, but best I can recall they're stock diameters.

What is primary POE... Pull over enrichment ?  not sure. 

The MAB screw is turned down and believe is seated.

Inlet is the high flow rectangular seat i believe 0.132" size. Float setting is 1/4" from top of bowl.

[Cliff Ruggles]

Some models will have 6 tubes in the airhorn and primary Pull Over Enrichment.

71 jets and 44 rods would be a pretty lean set-up on this new fuel, what jets/rods were in it when it ran rich?

Changing jets/rods would have little if any effect on idle fuel A/F, so not sure what's going on there.  Idle mixture is controlled by the idle mixture screws provided there is enough fuel coming down from the idle system for the application.

Is it being used on a stock engine, or has the engine been modified?.......Cliff

[jlutz455]

Ah gotcha, I just have the 4 tubes in the rear of the airhorn, no POE tubes as referenced in your book.   

I had 74 41 combo when the carb was rich at cruise and idle.

Engine has headers, 9:1 compression and bigger cam. I bought the car used, so not sure the cam specs. 

Not sure what to try next.

[Cliff Ruggles]

For sure 74/41 would be rich on the primary side with that carb number. 

If you are happy with the primary side tuning and how it works, use the secondary metering rods to tune full throttle.

Since metering rods have different dimension, taper, tip length, included angle to the tips it sometimes becomes difficult to tune with them at WOT.  I use and prefer custom machined rods for that purpose, so we can make educated changes without changer hanger height.

I'd try going to metering rods with larger tips until you get the A/F in the range you are looking for.  We can machine any size you would like, or several sets in different sizes for that purpose.....Cliff

[jlutz455]

Cliff...so you could machine a 44 primary rod with a 0.036" power tip?  If so that'd be great, how do I order that?

Another thought, if my power piston spring is too light, would that cause it to be rich at WOT ? 

[Cliff Ruggles]

No, we don't machine primary metering rods to tune full throttle A/F, we use the secondary metering rods.....Cliff