Author Topic: #7044270 Secondary POE Restrictions  (Read 155 times)

Offline Brian B.

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#7044270 Secondary POE Restrictions
« on: April 14, 2021, 03:10:03 PM »
Hello.  Would anyone kindly be able to confirm what the below factory stock measurements should be for a '74 SD. AUTO 7044270?  Thank You.

Secondary POE Well Restriction
Secondary POE Restriction
Secondary Tube Restriction






Offline Kenth

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Re: #7044270 Secondary POE Restrictions
« Reply #1 on: April 14, 2021, 11:32:56 PM »
Hi.
In my notes on 7044270 i have:

Secondary POE Well Restriction .034"
Secondary POE Restriction .077"
Secondary Tube Restriction ..049"

I spent an afternoon tuning a friends 1974 T/A 455SD using a racing camshaft and i could not have proper WOT respons with the closed airvalves on this unit. Replaced those with the earlier airvalves that has the large cut-outs and the car ran like a demon thru the gears. Owner went home with a big grin all over his face.

Final jetting after this session, #75 jets (.076"), #45 pri. rods, .041" idle tubes and .066" idle down channels. Also CC secondary rods, K hanger.

Offline Cliff Ruggles

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Re: #7044270 Secondary POE Restrictions
« Reply #2 on: April 15, 2021, 05:04:47 AM »
CC secondary rods are HORRIBLE, too fat up top and too small on the bottom.  I refuse to use them for tuning as they need a pretty tall hanger to get them up out of the jets holes quite a bit to get a clean transition going to WOT.

I've actually had better success removing the notched Pontiac flaps and installing solid ones that the other way around IF the holes were under the flaps or directly in line with them with a large opening exposing some of the entrance under the flaps. 

Another neat trick when tuning the secondaries is to leave a very slight amount of slack in the linkage so it can "tip" back just a tad exposing the POE holes to the underside of the flaps and fuel from the holes directly to the intake........Cliff

Offline Brian B.

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Re: #7044270 Secondary POE Restrictions
« Reply #3 on: April 15, 2021, 05:55:41 AM »
Thank you gentlemen.

Kenth.....did your friend leave the Secondary Restrictions stock or were they enlarged.

Cliff.....do you prefer rods along the order of AX or DA?

Offline Kenth

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Re: #7044270 Secondary POE Restrictions
« Reply #4 on: April 15, 2021, 10:46:04 AM »
We left the restrictions at .077", which are the largest to be found in any Quadrajet and common in Pontiac high performance carbs.
Also, we found the initial discharge was improved going to the cut-out air valves making the CC rods actually worked as intended.
High numerical rear end gears and high stall converter may have helped jetting with CC rods in this 455 SD engine some.
Respond at WOT was instant w/o hesitation of any kind.

Offline Cliff Ruggles

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Re: #7044270 Secondary POE Restrictions
« Reply #5 on: April 16, 2021, 03:02:32 AM »
I've lost count of how many times I went to test carbs that used CC rods in them and the engine "puked" all over itself going quickly to full throttle.  A quick bend on the hanger with a pair of pliers to get them out of the jet holes and problem solved. 

Instead of bending hangers or looking for higher ones I just replace them and all the issues go away with no other tuning needed.

This is also interesting Kenth and something you need to know.  We were on the dyno with a 455 and making pulls on it.  A/F was showing a tad lean with a set of CV rods so I tossed in a set of CC's.  Going from .052" down to .030" should have fattened it up some correct?

Next pull it showed even leaner with the CC's in it!   Those rods don't have nearly as smooth of a transition to the skinny tips as other rods and fat section right above the skinny tips, so unless you get them up pretty high you can actually go leaner even though they have really small tips. 

I've repeated that testing several times and did some track testing with them as well.  This was early in my learning curve and I decided to custom machine a complete set of rods from the same cores.  I very carefully machined those rods from the same cores with the same tip length and included angle leading to the tips starting at .030" and going all the way to .060".  Next time I went up on the dyno metering changes were spot on and very predictable.

I still have those custom machined rods today and use them when tuning at the track.  I've also machined quite a few sets for dedicated drag racers who run in various classes, Pure Stock, FAST, SA and Super Stock.  It eliminates the need to "juggle" hangers around with different profile and tip size secondary rods and makes things a LOT easier when you tune.  Once you find a hanger that makes the grade for perfect transition you just change metering rods based on the weather, Density-Altitude, etc.......FWIW.....Cliff