Hi all,

I have an '81 Bronco with a 300 and a 650cfm spreadbore Holley 80555 QJ replacement.

I also have a wideband O2 sensor on it.

When I first installed it, it ran really rich. Cruise, idle, WOT, everything, was around 10.0 - 12.5 AFR.

I leaned the main jets out considerably (from 64 to 58) and placed wires in the idle fuel passages in the metering plate.

It now cruises around town and on the interstate at a nice 15.0:1 AFR.
Part throttle accel is around 13.5.
It'll drop down to around 12 - 12.5 AFR once the power valve opens up.

However, once the secondaries open up and I'm in WOT, it's still 10.0 - 10.5 AFR. Just very rich.

I put some wire restrictions in the two small holes on the bottom of the metering plate on the secondaries side but it didn't change anything. Not sure if that's what meters them or not, but I couldn't find anything else.
I've also tried several different secondary springs.

Any idea on why the WOT is so terribly rich? I'm sure it's dipping down into the 9:1 range but 10.0 is the lowest the meter goes.

Thanks for any insight.

 

Do you have a sec. jet plate or metering block ? You could change the the plate or change the jets , Or change the sec. spring [ slower rate of opening the throttle blades ]

 

The carb has a metering plate, so there aren't any jets. There are smaller plates, but wouldn't restricting the passageways in the current one simulate that?

I've tried all the springs, but it's still the same once the secondaries open. The AFR drops like a rock.

 

got to ask , why such a big carb ? With 2" sec throttle bore it would be hard to tone it down , best you can do is a black spring and and change out the the sec plate [ came with a 34R9716-54 ] . Last resort would be drilling the sec air bleeds [ not recommended by Holley ] or admit the carb is just to big and move on . My 2 cents Good luck

 

I had a Holley 390cfm for a while and it got terrible gas mileage. I regularly got around 11 - 13mpg on the open road. I swapped out to a 600cfm Holley just for the heck of it and my mileage jumped to around 15 in town and 19 on the freeway. However, the low end left a little to be desired with both primaries and secondaries being around 300cfm each.

So, I decided to give the 80555 a try since, even though it's overall cfm was more, the primaries were significantly smaller.
Overall, it's been really nice. Snappy throttle, nice mileage, etc. I know I'll never use all of the secondaries, but oh well. (And it sounds and feels awesome when they open up!)

If I can get the secondary AFR toned down, I'm golden.


The Holley tech I spoke to said that the plate it comes with is equivalent to a 73 jet I believe. The next size down is about a "68". I may just have to give one a try.
The main reason I was curious about it is I tried restricting the fuel passages in the metering plate with wire and it didn't make any difference, which was odd to me.

 

Did you have to spend much time tuning the accelerator shot?

 

On the 80555? Not really. It came stock with a size 40 squirter and an orange cam in the #2 position. I swapped the cam out for a green one and it seems to do really well. I think a little bigger squirter might even be in order too (so I'm thinking of getting a 42 or 45), but overall, it has very few issues to speak of.

 

Yep - on the 80555. The idea of running smaller primaries for the snappier response off idle makes sense and if you had to do minimal work on the accelerator pump shot then it would be worth keeping in mind.
Thanks

 

Okay, I think I found something that should work.

http://www.ebay.com/itm/AED-Holley-CARBURETOR-Adjustable-Jet-Plate-Conversion-kit-1850-4160-600-CFM-CARB-/191256684434?pt=Motors_Car_Truck_Parts_Accessories&hash=item2c87c96792&vxp=mtr
AED Holley CARBURETOR Adjustable Jet Plate Conversion kit 1850 4160 600 CFM CARB



It's a metering plate that you can adjust using standard jets. Pretty cool setup.