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

Here you can see how I routed the MAF wire around the carb and in through the firewall to mate with the digital vacuum gauge

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

ok as with any wiring installation things usually have to get uglier before they get better

we had to yank out all the AFR gauge wiring and its controller to mate it with the new digitial vacuum gauge

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

I protect all my gauges with inline fuses, in this case the digital vacuum gauge calls for a 2 Amp fuse

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

and there it is sitting right along the side of the AFR gauge, fits perfectly

I was a bit surprised that I was only pulling 15 inches of vacuum, thought it was much more than that

here are the specs of my GM hydraulic flat tappet camshaft

Part # 24502476

Lift: .435" intake, .460" exhaust

Duration: 212° intake, 222° exhaust @.050" tappet lift

Centerline: 109° ATDC intake, 116° BTDC exhaust

Lobe Separation: 112°

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

alright so the whole point of getting a vacuum gauge was to tune the carburetor to have the highest vacuum at idle, so here we go


below we only mess with one thing at a time so in this case we were only turning the Idle Mixture screws to change the idle mixture, we were basically allowing more fuel in to see what the impact would be on vacuum

undesirable results are in red


-TIMING- - - - - - - - - - - - - - - - - - - - - - - - - - - IDLE - - - - - - - - -IDLE - - - - - - AFR - - - - - - AFR
ADVANCE - - - - - RPM - - - - - VACUUM - - - - - MIXTURE - - - - - - SPEED - - - - - LEFT - - - - - RIGHT - - - - - - - - - COMMENTS

- 10° - - - - - - - - -590 - - - - - - - 15" - - - - - - - -1.50 turns - - - - - -1.5 turns - - - - - 13.5 - - - - - 13.6 - - - - - this is where we started (carb bench tunned to factory specs)

- 10° - - - - - - - - -580 - - - - - - - 15" - - - - - - - - 1.75 turns - - - - - 1.5 turns - - - - - 12.2 - - - - - 12.2 - - - - - we richened the mixture by quarter turn out (vacuum stayed the same at 15")

- 10° - - - - - - - - -540 - - - - - - - 13" - - - - - - - - 2.00 turns - - - - - 1.5 turns - - - - - 11.4 - - - - - 11.6 - - - - - we richened the mixture by another quarter turn (vacuum dropped to 13")


ok, alright, clearly we are going the wrong way, the mixture is getting richer and richer, ok now we know (and we couldn't lean it out any more cause that would drop the RPMs below 500 and the truck would die)

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

ok, so we return the carb back to the bench tune of recommended factory specs, Idle Mixture 1.5 turns out and the transfer slot .020" showing (little square)


and now we only mess with the Idle Speed screw to change the idle speed / transition circuit (the infamous transfer slot), we were basically raising the RPMs to see what the impact would be on vacuum



-TIMING- - - - - - - - - - - - - - - - - - - - - - - - - - - IDLE - - - - - - - - -IDLE - - - - - - AFR - - - - - - AFR
ADVANCE - - - - - RPM - - - - - VACUUM - - - - - MIXTURE - - - - - - SPEED - - - - - LEFT - - - - - RIGHT - - - - - - - - - COMMENTS

- 10° - - - - - - - - -590 - - - - - - - 15" - - - - - - - -1.5 turns - - - - - -1.50 turns - - - - - 13.5 - - - - - 13.6 - - - - - this is where we started (carb bench tunned to factory specs)

- 10° - - - - - - - - -640 - - - - - - 15/16" - - - - - - 1.5 turns - - - - - -1.75 turns - - - - - 13.3 - - - - - 13.5 - - - - - we increased the RPMs by a 1/4 turn in (vacuum went up to 15/16")

- 10° - - - - - - - - -750 - - - - - - 16/17" - - - - - - 1.5 turns - - - - - -2.00 turns - - - - - 13.1 - - - - - 13.2 - - - - - we increased the RPMs by another 1/4 turn in (vacuum went up to 16/17")


ok, so now we are going the right way the vacuum is creeping upwards a little bit and the AFR is staying the same for the most part ~ I think we are learning it will take a little bit of both Idle Mixture and Idle Speed screw adjusting to find the sweet spot with the highest vacuum, hey nothing we didn't know already, but now we have a vacuum gauge validating what we are doing, seeing, smelling, and hearing

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

ok so after mocking with just the Idle Mixture screws and then just with the Idle Speed screw, it was now time to mess with both

so for this part we leave the Idle Speed screw at 2 turns turned in (so 1/2 a turn beyond the sweet spot of exposing just a .020" transfer slot)

-TIMING- - - - - - - - - - - - - - - - - - - - - - - - - - - IDLE - - - - - - - - -IDLE - - - - - - AFR - - - - - - AFR
ADVANCE - - - - - RPM - - - - - VACUUM - - - - - MIXTURE - - - - - - SPEED - - - - - LEFT - - - - - RIGHT - - - - - - - - - COMMENTS

- 10° - - - - - - - -550/750 - - - - -15/16" - - - - - - 1.25 turns- - - - - -2.00 turns - - - - 15.x/16.x - - - 15.x/16.x - - - - when we leaned out the mixture by turning the screws 1/4 turn to only 1 1/4 out the RPMs wigged out and we were way too lean

- 10° - - - - - - - - -700 - - - - - - 15/16" - - - - - - 0.50 turns - - - - - -2.00 turns - - - - - 14.x - - - - - 14.x - - - - - this yielded a 14.x AFR but its at the 1/2 turn minimum (the minimum being 1/2 a turn the maximum being 4 turns guideline)

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

so where do we go from here, well here are our choices

1. leave it where it's at (don't like this option cause it's right on the edge of lean with it being just 1/2 a turn out)

2. adjust the distributor advance lets say from 10° to 12° (this is free and will cost us nothing)

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

I am going to go with option #2 and first increase the timing advance on my genuine GM H.E.I. Distributor part number 93440806 here are its specs ie advance curve

Mechanical Advance: - - - - - - - - Vacuum Advance:
- - - - - - - - - - - - - - - - - - Vacuum
RPM - - - - - Advance - - - - - (in. Hg) - - - -Advance
1100 - - - - - 0.0º - - - - - - - 3.00” - - - - - - 0.0º
1600 - - - - - 12.0° - - - - - - 7.50” - - - - - - 20.0º
2400 - - - - - 16.0º
4600 - - - - - 22.0º

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

Don't run carbs or sbc's but enjoying your writeup. Thanks

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

thank you for the kind words, I hope to keep your interest

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

well gentlemen I have thrown a bunch of numbers at you and that's all fine and dandy but it all don't mean nothin' if the truck don't run good and don't drive good, am I right?

so how is the driveability?

well it's good, actually it's very good, the best way I can describe it as I get closer to the 14.7 magical number AFR for my idle circuit is that the truck feels LIGHTER, it no longer feels like I am pulling a 2 ton truck ie 4,000 lbs it feels like a hot rod, for real

the Goal being:

Idle = 14.x AFR (this is the P.I.A. hard to get still consistently)

Cruise = 15.x AFR (we got this, so that's good) whoa Greg aint that too lean? no everything I read says at part throttle cruise, ie you in truck with one arm around your girlfriend on the bench seat cruisin' at 70 MPH down the highway (praying the wife don't catch you, jk) only takes maybe 30 HP to move that truck so lean aint dangerous cause they aint a huge load on our rigs, read up on it fellers it's facinating stuff

but we are not out of the woods just yet, I am learning that this 4160 carburetor although a very good carb, (for 93% of us daily drivers, not 92% not 94%, ha ha but 93%) is NOT very tuneable

say what?

allow me to explain, it would be better if I could tune two other things, one being the idle air bleeds (tiny vertical pipes in the main body of the carb) and the second the idle feed restrictions (tiny little tunnels in the metering blocks) again neither adjustable on the 4160 carb (can we say Quick Fuel Technologies... stay tunned)

pics of me trying to get to 14.7 AFR at idle

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

well the Manual Steering conversion has been kicking my butt on my truck Restoring Rusty - Manual Steering Conversion but in the meantime I have been acquiring books and reading up on all things Holley carburetor, hee hee

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

having read up a bit I have some time to mess with the tunning a bit more tonight, remember the problem is that I still can't lean out the Idle circuit enough to 14.x Air Fuel Ratio which makes my WOT run way too rich at 11.x and 10.x per bank

so tonight I am going back to square one and adjusting what most of us take for granted the Float Levels which effect the air fuel ratio, when you lower them you lean out the mixture when you raise them you richen it up, believe it or not the carb is gravity fed, so the more fuel in the bowl the heavier it is so it pushes harder out the main jets into the wells, less fuel in the bowl the lighter it is so it pushes less

my truck started out at 13.x AFR this evening after driving it home from work and being totally warmed up, after I adjusted both float levels (primary and secondary by half a turn clockwise) I leaned out the ratio to 16.x that's too much but then I richened it up by turning out the idle mixture screws which gave me a happy 14.x

TDT - Test Drive Time to see what that did to WOT Wide Open Throttle from 2000 RPM to infinity and beyond

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

man this 4160 budget economy OEM style Holley carburetor is killing me I just can't get it to idle at 14.x Air Fuel Ratio

I have now nearly bottomed out the fuel floats by going one whole turn clockwise from bottom of site hole

I even replaced the 65 main jets for the smallest ones in the Holley tuning carburetor kit which were 64s and still the best it does is idle at 13.x

I know what is in need of adjusting the idle air bleeds or the idle restrictors neither of which are tunable on this carb without drilling things, and I don't want to do that

so next month after pay day I am converting this thing to a 4150 carb, I may even get the center hung float bowls that have the sight glass in them because this pull the plug out and watch fuel drizzle out when you bump the truck with your hips may have been cool in 1969 but it aint no longer

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

Does it idle best at 14.x:1? Or is that just your target?

I usually set idle mixture as lean as I can yet keep the engine happy and stable. It's not always 14.7, it's usually richer, like into the 13's. But - not all engines are equal.

Idle mixture ~shouldn't~ affect WOT, since idle ports and transition ports/slots require vacuum to work, and WOT should have zero vacuum - all venturi, baby, yeah! Float level will affect everything.

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

It is just a target / goal.

I understand how time of day can even effect a carb so that optimal settings are just hypothetical, but I still want a carb to be able to reach that ratio even if most of the time I am happy like you with a 13.x

I hear you, however please check out Gerards Bob2000 webpage at Carburetor Tuning the Scientific Way I think the guy has been there and done that plus he is an engineer from Cal Poly, so all in all smart dude. He reiterates what I have read in other places that the circuits build on top of each other, Idle + Transfer + Main + Power Valve

I have included a diagram from his site below

thank you for your comments I am a newb at this and not trying to hide it, every bit of information helps as I am learning

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

I know if you tune a ls motor it runs a hell of a lot better and stronger than factory. not sure if these are relatable in anyway but just throwing it out there. What's the main benefit of tuning in a carb this much? HP gains? sorry if you already explained the purpose of this lol read 70% of it tbh

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

actually this is not tuning it much at all, I am just going very slowly and documenting everything even my mistakes and struggles, once you know what you are doing and assuming you have a fully tunable carb (which mine is not, non of the Holley street carburators are, Demons are more tunable and Quick Fuel are fully tunable) you can be done in an hour

there are benefits to tuning both types of engines, carburated and fuel injected ie throttle bodied, the fuel delivery system does not matter

the newer engines such as the LS are able to run leaner I think (at cruise 17 maybe 18 AFR) but I know nothing about them (yet) so that's why I focused on what I had and began with a carb motor, if I did an LS swap on this truck I would be doing the same thing to tune it, plus these types of DIY diagnostic tools did not exist in the 70s and 80s unlike the LS motors that come with ODBII computers and Oxygen Sensors from the factory.

in my case I have a scenario where I bought an "aftermarket" Holley carburetor, (like most or many Hot Roddres go out and do) in all fairness a very good one but as most manufacturers do, it is pretty much designed to do all things to all cars, ie run on as many different cars as possible, which equals more sales (I am not a synic here just saying) so Holley tunes it to do so

also Holley don't want some dude to run it too lean and blow up his engines than go on some forum and complain about a bad Holley carb, so out of the box they come out a bit on the rich side to keep the engine from overheating and bad things happening

for a carb small block chevy I like heuristics ie rules of thumb, and over the last few months maybe years I read enough to sort of have these fuel ratio guidelines (have I tested them on a dyno yet, no, but its coming up very soon)

Idle should run at 14.x AFR Air Fuel Ratio (13 is acceptable)

Cruise should run at 15.x AFR Air Fuel Ratio (16 is acceptable)

Power should run at 13 (not 13.5) Air Fuel Ratio (though my old dyno guy said SBCs generate the most power at 11.5) well we shall see

I hope I am answering your question.

So who am I who do I think I am?

I am just a guy who likes to get his hands dirty but not fly by the seat of his pants, ie I don't believe you tune an engine by saying yup that sounds about right, or by putting your hand against the exhaust pipe and going oh yeah that feels right. COME ON MAN, have guys tuned their trucks like that for decades, yes sure absolutely, does that mean they were tuned properly, I strongly doubt it as there are some such subtle differences in the air fuel ratios that you can make that they do not change the RPMs where the human ear can pick the differences up nor the exhaust pulse yet the ratio can change by as much as a point

Yes AFR gauges are still very expensive but they are invaluable,

• not only for fuel efficiency

• but health of your engine (I may have discovered that the passenger side bank on my engine runs richer than the driver side - is one spark plug fouled up and missfiring, is there some other issue?) I would not find this other wise

• And Yes finally for power, but I say finally not firstly as it is super important to have everything else in order first, a lot of youngsters [ahem] and oldesters, ha ha, skip the idle circuit and head right for the power valves right for the squirter ie accelerator pump - hewk I know of many cases where going smaller jets and smaller fuel pump nozzle improved the performance of the vehicle not the other way around

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

wow, very detailed response! thanks. bookmarked for future references. This part makes me feel somewhat better i guess lol i tried to dial in my carb/motor the "right" way with the vacuum gauge and a timing light. It still runs like crap but better than nothing right?

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

thought I would share what the laptop now looks like with the four virtual gauges, now that the Vacuum/Boost gauge added both the RPM gauge and the Vacuum gauge

check it out, now we are getting somewhere

now ideally I would want two more gauges for a total of six, the additional two that I am after are the Speedometer, ie vehicle speed, that is important because today you can't tell if the vehicle is under load ie moving or sitting at a stop sign and me just reving it up, the second gauge I would like to add is the crank position sensor to show me my timing advance as I drive ie Part throttle on the freeway say at 70 MPH and or WOT wide open throttle (on [ahem] a test track)

Note the near perfect 14.x idle ratios and I usually pull about 18 inches of vacuum at idle so not bad

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

So a quick update at where we are at now

Idle - 14.x excellent

Cruise - 15.x very good

WOT (Wide Open Throttle) - 12.x driver side / 10.x passenger side way too rich, not good

the 4150 conversion kit should arrive any moment now, we will see if that helps

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

yet another book to read, this one is recommended by my favorite author Jeff Smith so it ought to be good

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

and the Holley carburetor conversion kit finally arrived today, so excited to convert my 4160 into a 4150

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

nothing like a clean workbench

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

some parting shots of my 4160 carb in its 4160 form

and with the air cleaner removed for a better look

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

and here she is on the workbench ready for disassembly

Holley 4160 Carburetor (with one metering block and one metering plate) about to be converted to a Holley 4150 with two metering blocks

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

first we remove the rear float bowl, this exposes a metering plate and the blue metering plate gasket

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

I have no idea why Holley decided to use those pesky clutch bit screws in the metering plate, in my opinion there was absolutely no reason for it, but they were no match for one of my smaller flat screw drivers thank god

removing the metering plate exposes the blue gasket and removing the gasket exposes the carburetor body, the main body

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

here we take a closer look at the metering plate off of the carb

note how there are no provisions for the jets or for a power valve, what you see is what you get

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

here we stare and compare the metering plate to the new metering block

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

now we get ready to put it all back together

we fit the gasket on the metering plate to make sure nothing gets pinched and that it is going on the right way

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

we screw in the jets, I decided to start out with the 65 jets and go up from there

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

we mount the block to the body

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

and here is our "Wanna Be" 4150 carb

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

well something that I should have done already but I kept putting it off was checking the spark plugs

this is the passenger side - I don't know about you but they look perfect to me

from left to right: #8 - #6 - #4 - #2

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

alright well lets take a look at the spark plugs on the driver's side

from left to right: #7 - #5 - #3 - #1

Oh my that can't be good

Check out the #5 plug the second one from the left, that be what we call carbon build up it's hard as a rock

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

Curious that its only one cylinder. Aren't deposits usually a sign of liquid (oil, fuel, antifreeze) in the combustion chamber?

If that's true, not sure how it could be fuel only on a single cylinder?

My final unfortunate guess, would be valve guides, rings, or headgasket...

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

Tell me more about rings, cause I rebuilt these L31 Vortec heads that I got off of a 1999 Suburban with only 135,000 miles on it only in March, but I did not touch the bottom end, ie my original 1974 short block. So the heads have brand new valve seals, and I lapped each and every valve for a tight seal.

I am no expert in engine lubrication so I am just wondering how likely is oil to get into the cylinder from under the piston, if that's how faulty rings would allow it in there, anything else has to come from the top right?

The headgaskets are brand new, also put on in March

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

New seals on worn guides won't keep the oil out as well as new seals on new guides will. I don't recall - did you measure valve guide wear whilst it was apart?