Holley tuning/question on jets/placement

[BB73Challenger]

So in my offseason, I've decided to get some things cleaned up on my motor & long short I've come around to jetting on the carb and have some questions 

Holley 850 - DP - power valves primary & secondary

After working out my idle circuit and transition with squirters & cams, I'm now looking at jetting.

Curious that my primary has 80 jets & secondary has 78's.
It would make sense to me that if anything the secondary would be heavier... am I on the wrong process here?
How about square jetting?

I figure without an air/fuel meter that plugs and ultimately quarter mile numbers will be my best indicators.

Any thoughts and opinions are as always greatly appreciated!

Happy Holidays to all as well!! 

[MEK-Dangerfield]

Jeff,

  I have a Proform 850, so it's you carb's evil twin.   

It came with 78's in the primaries, and 86 in the secondaries. My carb has a choke, so it makes sense that the secondaries have more flow.

I'm not sure why your's is set up like it is, but how do the spark plugs look?

[Chryco Psycho]

I have never seen a situation whee the front jets were bigger , something is not right , I think Proform has a spec list on the internet for the carbs so you can change back to stock & start from there

[BB73Challenger]

Jeff,

  I have a Proform 850, so it's you carb's evil twin.   

It came with 78's in the primaries, and 86 in the secondaries. My carb has a choke, so it makes sense that the secondaries have more flow.

I'm not sure why your's is set up like it is, but how do the spark plugs look?

Yeah I've seen a few sources that confirm the larger 80 primary & 78 secondary numbers, and that just seemed odd.
I got idle knocked down delivering a dark tan/brown plug but as I started logging more street drive time they turned out a bit "sooty".
They then clean right up with a jump on the freeway.

I have a nice crisp off idle response & even pulling in 2nd when I stab the throttle the tires break loose pretty easy.

I know I'm not far off, cold/hot starts good, just looking at some very fine tuning 

[BB73Challenger]

I have never seen a situation whee the front jets were bigger , something is not right , I think Proform has a spec list on the internet for the carbs so you can change back to stock & start from there

Oddly enough I started looking up stock setting info when coming to the realization of the jet sizes!

[BB73Challenger]

The carb's ID number is 4781-8 - a lot of sources go up to 4781-5 but even they are listed at 80 F 78 R

[MEK-Dangerfield]

Yeah I've seen a few sources that confirm the larger 80 primary & 78 secondary numbers, and that just seemed odd.
I got idle knocked down delivering a dark tan/brown plug but as I started logging more street drive time they turned out a bit "sooty".
They then clean right up with a jump on the freeway.

I have a nice crisp off idle response & even pulling in 2nd when I stab the throttle the tires break loose pretty easy.

I know I'm not far off, cold/hot starts good, just looking at some very fine tuning 

Jeff,

  You are definitely close. More than 5 sizes off, and you would feel a "miss". It sounds like your primary jets are too large. Maybe go 78 all around.   

[Chryco Psycho]

good starting point going to square jetting

[BB73Challenger]

Sounds good guys 

With that evil white stuff from the sky just starting here I've got a lot of time ahead of me for some tweaking