Holley 4150 tuning
 

I have a Holley 9022 800 CFM carb on a 439 cid BBC...

When the secondaries start to open it goes RICH.....

I have 75 jets in the primaries and 86 in the secondaries...(no secondary power valve)

A/F ratio on just the primaries is 12.8:1 cruising at 3000 RPM.

A/F ratio is 12.5:1 at full throttle.4800 rpm (prop is a bit too big)

At 4000 RPM, when the secondaries are just partially open, the A/F ratio is 10.5:1... Any way I can tune this out ?



THANKS !

Doug

yes.install a power valve with a lower number so it does not open as soon.

would you want a lower number?

Very possible ^^^what he said^^^^ - this can be determined by using a vacuum gauge in accordance with the wideband A/F set up.

It could also be:

Is this exactly when the secondaries are starting to open ? If you leave throttle there for a few seconds or more, does the A/F ratio come back up a little ?

Reason for asking is that since this is a DP, the secondaries have a accelerator pump also. As you know, the pump shot starts right as it's throttles are being opened.

yes,i just woke up so not thinking yet.i will fix my post.

You need a Java Shot, not a Pump Shot. LOL.

It stays constant at 10.5:1 while cruising.. I would estimate that the secandaries are open about 1/4 of the way at this point...

Don't estimate. Put a gopro over it or mark your hand throttle level where sec are just starting to crack open.

I had the hatch off and was watching it.. 3000 RPM is definitely when the secondaries just start to open...

I was estimating the amount of secondary opening at 4000 rpm.... :)

Sounds like you need to go with a smaller secondary air bleed and jet. If I am recalling correctly air bleeds tend to add a greater percentage of air with increased cfm. So the Air bleed is giving you a rich to leaner condition as air flow increase through the carb. You need to size the air bleed so AR is constant then jet accordingly.

I would try a later opening power valve. Like a 2.5 or 3.5. Your carb most likely doesn't have screw in air bleeds. I wouldn't mess with them at this point anyway. You have good cruise, good wot, but too much fuel being introduced at 4000. If you add change primary jet, you change your afr at 3000, and wot. . If you change secondary jet, you change wot afr. If you changed PV restrictor size, you change wot afr again. If you change air bleeds, again you'll be changing the curve, as well as the afr at wot,

You have the right amount of fuel going in. You just need to delay the dump of fuel coming from the PV opening too soon. Just my thoughts.

I agree. I wish more carbs had replaceable power valve channel restrictions. Between those, jets, and PV's, a lot of 'secondary enrichment' tuning can be done.

Its sweet. Icdedppl and i just did this on his blower carbs. Boost referenced. Pvcr's were large stock. Unscrewd them, went with smaller ones, afrs went from high 9s, to almost 12.0 at 3500rpm. No jetting changes, and overall fuel curve is very nice. Without that option, he would only be able to really change primary main jets, and that would have been extremely lean at 3000rpm before the pv opens. Having a power valve itself is a nice option, being able to control when it opens, AND how much fuel it delivers , is a cool feature.

Cool deal.

Furthermore many don't realize, a PVCR is a jet. Who wouldn't want to be able to change it ?

Sure, bleeds are nice to be able to change, but that would get most people up over there carb tuning level.

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im so jealous of this knowledge, I have a carbed motor and am like the soccer mom driving her minivan, "clueless about whats happening in the engine"

Sure is easier to tune with power valve restrictions and boost referenced carbs where the power valve opens as soon as boost comes in.
If I were to do it all over again with carbs that do not have such provisions I wouldn`t use power valves and just tune with primary/secondary jets.

Best way to learn:
1)Buy books and read over and over again.
2)Then, get down and dirty...try things you think you've learned and keep good notes on what changes do what.
3)Break schit.
4)Fix schit.
5)Then maybe break and fix schit a few more times.

Then, you'll become an intermediate tuner / repairer.

To become a pro, you'll need to break and fix a lot more schit.

Hah !