Recipe #1 Question

[Tuffnut]

Recipe #1
Cliff, I'm trying to follow your recipe #1. My carb is a 1975  7045250 with the aux piston/rod. I bought the kit off you to plug the aux piston hole which i did, plugged the aux rod jet with the lead sinker, new accel pump, new needle & seat, new heavy spring for the power piston and replaced the existing .067 jets with the new .073  jets and .041 rods with the new .044 rods for .029 difference between the jet & rod. Also adjusted the float to 1/4" from 7/16" as per the book. Had it started up runs good at idle and responsive. Slight hesitation around 1500 rpm . Too snowy here to take it right now for a rip. Car runs 1975 350 olds with rebuilt #5 heads, 16" vac with and Rv cam, Dual exhaust, new pistons bored.030".

Should I be looking at the main air bleeds for proper opening of .070" ? I can't get my head wrapped around which ones they are by the book compared to what I have . Picture attached of the the actual carb body
Thanks
Jeff
Paris, On.

[Cliff Ruggles]

Leave all the airbleeds at the stock sizes for that carb number.  Once the weather permits do some testing, you'll probably find that it woln't need any further tuning, but you can add some fuel using the APT system if/as needed........Cliff

[Tuffnut]

Thanks Cliff for getting back to me...
Jeff

[Tuffnut]

Cliff after doing all the mods and doing some testing, the carb is running a bit rich at cruise.
There is no hesitation, no black smoke that I notice. When I do the tip in at 2000 rpm the engine drops rpm right way and same if I take off an vac line to the carb. It has lots of power though. I'm using .073 jets and .044 rods I got from you. My aux piston is closed off as per the parts from your kit. Adjusting the aneroid doesn't make any difference right now.
Weird part is I get slight surging at cruise, doesn't make sense if it is rich. I reset float back to 7/16" as well. Power piston with the heavy spring is working correctly, verified with the straw check, doesn't start to lift until around 2000 rpm under load in drive. Idle vac is around 16"-17"

I was thinking of going down one jet size which i have .072. This would affect cruise & WOT.
Problem is, I can't tell if I'm too rich at WOT. It's possible I may be as well.

Is it possible I may have to go up to a .045 or .046 rod instead?
These early aneroid 1975 carbs are not friendly. Not ready to throw in the towel yet.

Not sure which way to go, down 1 jet size or up a rod size.

Jeff

[Cliff Ruggles]

I'm not fond of those here and have had issues with enough of them to avoid them when possible.

It's a poor design as it has drilled passages leading under the jets to allow them to see each other, plus the length from the aneroid located APT to each jet is not the same.

Surging would indicate a tad lean at cruise or too much timing from the vacuum advance.

Dropping back to 72 jets will lean it up a tad at part throttle and a little and heavy/full throttle as well.  I'd try that first.

I've typically had to go smaller on the primary rods with those vs larger from the 73/44 set-up.

Make absolutely sure the power piston hanger arms are level and exactly even, big player there in what you are doing......Cliff

[Tuffnut]

Thanks Cliff, I will give those suggestions a shot.
Jeff

[Cliff Ruggles]

Make sure that you use the correct jets.  Most of what's being sold out there is NOT for a Quadrajet.  There are 4 different types of Rochester jets that look the same at a glance but the distance to the orifice varies for each type, as does the angles leading into and out of the restriction..........Cliff

[Tuffnut]

1. I was doing some reading last night on the primary power piston hanger adjustment. Since my power piston is non adjustable for a 75, (no APT) just an aneroid,  what would be the measurement I should be looking for?

Remove the rods from the hanger. Sit the piston /hanger assembly upright on a flat surface and measure up to each hanger arm. What distance should should I see from the flat surface to the hanger arm for each side?

2. Also I have used the heavy spring for the primary power piston based on 17" hg at idle. Starts to lift around 2000 rpm under load. Should it lift earlier. I don't want it to be too rich in the cruise.

Jeff

[Cliff Ruggles]

The power piston is engine load related (vacuum) not RPM's.  Stronger springs will typically improve throttle response as they have a quicker cut-in point.  With most engines all the springs we sell will be down at idle (lowest engine vacuum), unless you've installed some Thump-Ya-Mutha camshaft in a really low compression engine and are making about 5-7" vacuum at idle.  At that point the best tuning method would be to remove the cam and tink it off the nearest dumpster and put in something better chosen for the application.

If my comments sound a bit sarcastic, well, I really trying to help folks out.  Despite all the great information out there (that we never had back when I got into this hobby) folks still make piss-poor parts selections for these engines.   Not a day goes by I don't get a call from some poor soul wanting a carb or carb work for his engine because it refuses to idle below 1200rpms or so.  Yes, folks are putting 243/257 @ .050" cams on 107LSA's into 350 SBC engines with dished pistons and 882 heads.....then wondering why it doesn't do anything right!

The hanger arms should be level and exactly even on those PP's.

You can do a little custom fine tuning by very carefully raising each rod a few thousanths of an inch, and making them exactly even again, as long as the rod tips stay in the jets at the highest position. 

It's time consuming with those but you'll find you can come up quite a ways on the 44 rods and increase fuel at part throttle without the tips coming out of the jets when it's all the way up......Cliff