Hi guys.
As my car was, I had the jetting what I felt was optimal for my setup for many years now. THEN I go and look for that extra tenth or so in the 1/4mile.
I install a Proform Main body on my 4780-1 holley. Follow the jetting recommendation except because I have both powervalves I opt to go with 72/80 jets instead of the 84's they suggest. At this point I swear the car makes more power than with the stock main body but nowhere to confirm this.
Plugs looked really white now compared to before so I figure I'll up the jets a bit. I put a PV plug in the rear and up the rear jet to the 84's. Car feels weaker now. But who really knows?
So I go racing Saturday, 1/8 mile. And I've slowed down by 2/10's. Not impressed. So up I go in jet because plugs still look lean. 74/84 now. Car picks up about a 1/10 and I'm back in the ballpark. Now it rains. Track closed.
So in the downtime I go up to 76/84 and first run Sunday it picks up another .05 and I'm basically back in the neighbourhood of what it ran last month and for the last couple years.
Now I up the rears to make it 76/87. Car ran .002 faster than the last run but picked up another mph.
I usually can say the car will run a 7.40 +\- .01 @ 94.5 mph. I was now pulling 7.424 and 7.422 @ 95.6 and 96.33 mph. Never had mph like that before.

So now I wonder? Is this Hp main body gonna pick me up in the 1/4 even though I seem to have slightly slowed my ET in the 1/8? And does it sound like I'm on the right track here??

removing a power valve usually requires going up 8 jets sizes if you are running stock pvcr's. I don't think 80 to 84 is enough.

Sounds like you can still jet up.. did your 60' slow..
if so you might need to play with the squirters and
pump cam

I guess I'll keep jetting up I can get a few more runs in 3 weeks but there won't be 1/8 mile times at that track.
Crizilla, I thought it was 5 or 6 sizes, I'll go more thanks.

Mr P. I was a bit slower in the 60 but everyone seemed slower by .02 or .03 yesterday in the 60'

When I did the Proform main body swap on my carb I ended up jetted 82/92 for max power with a PV in the primary only (air bleeds were 36/73). The car picked up 3 tenths and 3 MPH over the stock main body. The plugs looked a little rich, but it made the best power like that. Keep jetting up until the MPH fall off, then back it up a step and you're set.

I also tried square jetting it at 92/92, it ran just a touch better at the track, but it fouled the plugs WAY faster.

So is it safe to assume that a 10 size spread from
Primaries to secondaries is good to shoot for? Say if I go up again on the primaries to 78/87 or 88. Sure is a lot more than the 72/84 starting point that they suggest. I'm excited to change it though and see what the results are. My plugs are just starting to show sign of colour.

What your going to run in to if you keep going up on the primaries is a pig rich cruise afr. If it's a drag car only that's usually either idling or WO that's fine, but if you drive it much the plugs won't last long. For a street/strip car it's a slippery slope, with Thumper and a couple other guys help I'm starting to get some traction.

I realize I can't just keep going up in jet size here. I really believe that by seat of the pants, this combo was more powerful with dual powervalves and 74/80 jets. Ever since I decided to block the PV it has felt soft.
So I'm going to get some smaller air bleeds in an attempt to speed up the fuel to the boosters. I can't help but think that this increase from 25/28 on the high/low sec bleeds to 36/36 is just pulling too much air and delays my fuel flow. The primaries are also up from 25/71 to 36/75.
The big problem up here is that nobody has air bleeds anywhere. Either I buy a 10 pack of 27's and drill a bunch of em or order them from Quickfuel and wait.

i just ordered some air bleeds from jegs, free shipping.

What you're going to find is that on a holley the circuits all stack up to be the final AFR. For the track it's pretty easy to tune for the fastest tune at WOT and you're getting there.

You can easily use the main jets to get the best ET, but a lot of street cruising is done mostly on gas mix coming out of the transition slot. This mix is regulated by the Idle Feed Restrictions (IFRs) which are only screw in jets on fancy metering blocks. The gas from these holes is emulsified and mixed with air from the low speed or idle air bleeds. On a race carb they will often be too rich for cruising without fouling your plugs. The way to tune this is to get the IFR size close either by sticking little Vs of wire (guitar string is cheap and .xx" exact) or if you're lucky with jets, or you can drill & tap make jets if you're handy. Once you're close you can fine tune with the air bleeds.

Watch out- when you tune the T-slots with the IFRs and idle bleeds you change the AFR of your whole idle system- which includes the four corner idle screws. These screws don't actually control the air/fuel ratio, thats the job of the IFRs and the air bleeds. They only control HOW mUCh of the mix drips/is pulled out of the idle discharge ports (little holes in venturis below butterflies).

I've found on racy holleys that I run on the street that the 4 idle screws can be a good indicator of how close the IFR/air bleed tune is. If you idle with all four screws out 3/4 turn then the idle system is too fat. Lean out those IFRs until you need to use 1 1/2 turns out on those idle screws. That should get you close to a nice lean tune for humming along just cracking the throttles.

Once you got that goin good move to the primary jets. You want a decently lean cruise on those too- this is where a power valve comes into play. On a chilled out highway speed trip you will probably get the throttles cracked open enough to use the primary main jets. The idea is to get them where it is lean but doesn't surge. If you drop the vacuum with more throttle it should start to get a little too lean and the primary Power Valve should open up and save the day with just the right amount of extra fuel. Of course the two holes under the PV (Power Valve Channel Restrictions) are another set of usually not tunable holes (a guess by holley at what kind of chevy 350 motor you have) so you can either get out the wires again or just get it as happy as possible.

So now you have the whole idle system and front 1/2 of the carb dialed in for razor sharp cruising and even a little economy. Fill in the holes with a little accellerator pump cam and jet selection and we're almost up to where you started- secondary jetting and power valve. A secondary power valve can help with extra fuel at WOT but it's not worth the risk and trouble- at the big end your high RPM could pull enough vac to shut the PV off and the motor will go lean. Not good. So skip the rear PV and just jet for ET/MPH and you're done.

Then check your plugs and decide if your fuel distribution sucks bad enough you can start all over.

Ha! Have fun- a carb is always a compromize but you can get them dialed in pretty darn well if you're willing to dig in a little and second guess the 'non adjustable' circuits. Jet changes alone usually won't get you there unless you only care about WOT

Some good info but you still can`t get the upper end(WFO)properly rich enuff w/upper 30 hi-speed bleeds and the angle channels need to be opened up if they`re in the 130`s 140`s like so many...........

Good info , guys! I'm getting closer (I think) to getting it all close enough. I couldn't care less about "perfect" afr's but don't want to kill anything.
So talking about secondaries now, if after my body swap, with nothing else changed at all, the power felt awesome at WOT. Then after blocking the rear Powervalve and going up 5 more jets (82 - 87) , in increments over 3 runs, it picked up speed in the traps, but lost hit in the 60ft. Got really soft off the line.
Wondering now if I need some more juice from the Squirters? Always had 35 front and 31 rear with a 50cc pump on rear (was in rear when I got this carb from a buddy years ago) maybe it might like a 35 squirt on the back too now.