I went from 85#'s to 79#'s in the front primary's on my Demon 850.
It's like driving a brand new engine. http://forums.performanceyears.com/g...on_biggrin.gif
Idle is better, car run's so much smoother, unbelievable the difference it made. Oil, voltage, I lost that gassy exhaust smell.
The #85's are what was in the carb from BG.

I'm so happy, I had to tell someone, my wife just didn't care....

YEa, sounds great. My efforts start out rich, then lean-up with run time on the road.

Secondary, then Primary, then Idle.
Along each adjustment, I reconsider the Initial timing. Just to match the off-idle response to the pump gas ping.

I Wrestle the High-Compression Primary&Idle recipe on: Rich&Advanced or Lean&Retarded. To the tune of having non-linear timing & a non-linear misture.
Q-Jet Part-Thrittle Enrichment circuit allows the Fat/Lean vs load, while the HEI initial Advance comes in early and stays put above 2500RPM.

I got my hands full with the 8.3:1 Mixture & Timing shedules. HIS

Hallelujah! I jetted down to 78's and 86's and had the same result. Woke the car up BIGTIME. even 80's are too big for my 455 with RA IV Cam rgoads lifters, balanced and blued 4 bolt block. Also saw idle quality improve and backfiring subsiding remarkably.

I've found the "sweet spot" for my Holley 800 DP using a wideband O2 sensor. 70 pri. with a 6.5 PV and 84 sec. PV blocked. Before I had the O2 sensor, I was running 77/85. Now it's a whole lot nicer to drive on the street, plus I knocked .3 off my 1/4 ET! http://forums.performanceyears.com/g...on_biggrin.gif

Rugratman: wives are like that. They only get excited about their next pair of cute shoes which they will complain about later that their feet hurt.

george

Hi,
How are you using an O2 sensor to determine your air-fuel ratio???
Do you have O2 sensors in your exhaust pipes (where?) and what type of instrument are you connecting them to?
I'd like to know if my jetting is correct also.
Thanks,
Mike

I'm using the Innovate Motorsports wideband with the RPM kit. Best money I ever spent on my car! http://forums.performanceyears.com/g.../icon_wink.gif I have the O2 sensor mounted in the crossover pipe so it can read both banks.

LM-1

Rugratman, what made you decide to change jets ? Were your plugs fouling ? I'm thinking I may need to change mine too but my plugs look fine.

ER

Rugratman, congratulations! Typically the aftermarket carbs are jetted rich for most applications (probably a liability thing).

I had the same experience with my Holley 3310. Dropped 4 jets sizes on the primaries and the part throttle and wide open AFRs came right in where I wanted them. Didn't even have to touch the secondaries (thankfully - I hate those cheap plates they used in place of real jets).

Car ran better and used less fuel (when being gentle of course).

Strangely, my wife wasn't excited either. Kind of kills the thrill of victory feeling.

I have 74 pri and 84 secondaries in my hp950 think im going to jump it up a notch LOL.
Mike

LouisianaGuy, I am running same hp950 carb with 78 jets front and rear. I did 74 front and 77 rear, power valves present but no street driving yet. What was your reason for a change? Just curious cause i am trying to fix rich condition
at low speeds. Thanks

Serge, I got the carb like that it was onan E-head 455, dont know if they jetted it like that or it came that way...I dont have a rich problem really, 74/84 I believe...I have to take it apart as I have a screw leak and would like to put new gaskets for grins.
Mike

firechickenman - glad to hear about your thumbs up to the Innovative Sports system. I installed a bung on each collector for this exact purpose. I'm trying to figure out whether to go to a chassis dyno or pick up one of the Innovative kits now. With what it would cost for one session at the dyno I could have one of these kits forever.