INNOVATE DLG1 Wideband O2 Oxygen Sensor Tuning Diagnostics Logging Air Fuel Ratio etc

[Gregski]

from what I can regurgitate from what I read, the rating (number) on the Power Valve says at what vacuum (negative pressure in PSI) the valve will open allowing more fuel to leave the fuel bowl and enter the main well

a Power Valve is a helper that says ah snap all this air is about to rush in to the carbie I better do something before those lazy cousins of mine the Main Jets kick in

J - E - T - S (.... what? too soon?) ha ha

so we will try replacing my stock default 6.5 PV with a new 7.5 PV this should shoot some gasoline in the engine 1 PSI sooner so as the vacuum drops from say 19 PSI as I am cruising as soon as it drops below 7.5 now the PV will open, before it wouldn't until it dropped below 6.5

the Power Valive lives in the front metering block (thank god) and can be replaced with the carb on the truck like so

[Gregski]

the Power Valve requires a 1" wrench, naturally the biggest one in my toolbox be a 7/16th so I had to use an adjustable one

be careful, the valve screws into an ALUMINUM block that is very soft metal, so you don't need a cheater bar to loosen or tighten it, ha ha

[Gregski]

the balck/gray gasket is horrible and separates in two like an Oreo cookie when you remove the old power valve, so please make sure to clean it off the block, I just used my high tech thumb nail to scrape it off and the bottom of my T shirt to wipe it clean, magic!

[Gregski]

new power valve comes with a new gasket (same terrible one) but oh well

[Gregski]

and back on the truck it goes, if you are running ported vacuum (black hose to the distributor diaphraghm) then don't forget to connect it back up, as you had to remove it to take the primary metering block out and bring it to your work bench, that vacuum nipple is on the block

[Gregski]

the Holley 4150/4160 carburetors are modular so they are fantastic to work on, as you can completely remove a component and not interrupt any of the other pieces, brilliant

the confidence you get from doing even a small job like this feels great, it really builds your knowledge and motivates you to take on other tasks

[Gregski]

blah, blah, blah Greg, so did this fix your hesitation problem?

Um, no, no change, lol, but hey Rome wasn't burnt in one day

so just for the heck of it and since I already bought it, we are going to give the 8.5 power valve a shot today (pun intended)

[Gregski]

So I tried the 8.5 Power Valve this morning and no change, so I still have a hesitation problem when I step on it and floor it in any gear at any RPM

I doubt it is the Power Valve unless I am supposed to go all the way up to like the 10.5 which I doubt

[Gregski]

let me show you graphically what this hesitation looks like

here I am changing from 1st (first spike) to 2nd gear (second spike the tallest one) and then flooring it in 2nd gear until I reach 2500 RPM (purple line) then I let off

what we are interested in is that huge red and green spike (about 13 seconds into the test, bottom axis), those two lines represent the Air Fuel Ratio in the right bank ie Passenger side cylinders/exhaust pipe and the left bank ie the Driver side cylinders/exhaust pipe

see how after I floor it they lean out all the way to 22 parts air to one parts gasoline, way too lean, and we are trying to prevent that

this is difficult because all these things happen in a second or less: as the vcuum decreases to less than 6.5 PSI (black line that goes flat to 0 PSI when WOT) the power valve kicks in, at the same time the secondaries open (they too are vacuum operated) and I don't know at what exact RPM they open yet, also the accelerator pump gives a shot of added fuel, all three in that one second

[Gregski]

Next step, put the default / original 6.5 Power Valve back in, essentially returning the carb to its original factory setting

again we like to play with and change one thing at a time

[Gregski]

ok so since we got the vacuum secondary springs delivered we will try changing those next

Holley Secondary Diaphragm Spring Kit
Part# 20-13

[Gregski]

we also ordered the Holley Quickchange Vacuum Secondary Housing Cover

Cover-Diaphragm Housing 1 x 4 bbl
Part# 20-59

[Gregski]

Good Morning, just another day at the office! ha ha

[Gregski]

well, so my carb didn't come with the Purple vacuum secondary spring like the spec sheet that did come with it said, ha ha, instead it had the plain spring, like so

[Gregski]

Holley recommends a heavier spring for a heavier car, so I figure Rusty (my truck) is 4,000 lbs it aint no Miata so we'll call him heavy and try the Brown spring first

[Gregski]

but first we mount that quick change pod

[Gregski]

old cap vs new

[Gregski]

had to do it off the carb, it was easier that way

this should make swapping springs way easier

[Gregski]

carb back together

brown spring in

ready for a test drive

[Gregski]

No luck with the stiffer Brown spring, going to go the other way now and try the Purple lighter springer

[Gregski]

alright so I tried the Purple lighter spring and holy cow things improved, the hesitation was almost gone but not quite - alright we was on to something here

this defied all logic but what the heck it's what my truck liked

[Gregski]

excited about the progress I went one step lighter and tried the tall yellow spring - and the hesitation was gone!

[Gregski]

the process calls for us to keep going until things get bad again and so I kept putting in a lighter spring and tried the short yellow one

things got worse - the hesitation returned

[Gregski]

so we backed up a step back to the tall yellow spring

test drove it and the hesitation was once again gone

and this is how you do it folks, you change one thing at a time, it takes patience and discipline but that's what tuning is all about, it's taking an engine that is running 90% good and finalizing that last 10% to make it perfect

[Gregski]

Alright this left us with a slight hesitation upon blimping it, aka flooring it while in neutral, it would go

vrooo vroooooom, instead of a smooth vrooooooooooooooooooooooom

so it was time to try a bigger accelerator pump nozzle or a different accelerator pump cam, I bought both just in case

my carb came with the .031" and the next size up is the .032" which I thought would not be enough so I bumped it to the next size up the .035"

let me tell you swapping the little nozzle is a major PIA, I had to take the carb off to do i, as those pesky little black washers kept falling on the butterflies, danger danger

the bigger squirter took care of the hesitation while flooring it in neutral and the truck is running BEAUTIFULY!