WBO2 and Holley carb tuning plans.

69427

69427

The Artist formerly known as Turbo84
Joined
Mar 30, 2008
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Clinging to my guns and religion in KCMO.
Once I finish the sway bar modifications for the '69, I'm going to pull the exhaust to weld on an O2 sensor fitting. I haven't done much tweaking to my Holley other than the usual rebuilds or repairs. Is there any info out there (or resident experts) that can help me out when I get around to tweaking the carb? I'm hoping to help out the idle quality a little bit (if possible), and perhaps monitor what the a/f ratio is during cruising conditions, and certainly, what the WOT a/f ratio is. Any Holley gurus out there available to answer some future questions for me?

Thanks,
Mike
 
This forum is great http://www.innovatemotorsports.com/forums/index.php. There are few really well respected guys on there ("tuner", "shrinker"). You can read their posts and get all the info you could ever want. I went around the barn trying to tune my BBC (LS6 with 288 AR10 solid roller) and learned more in one afternoon with my O2 and a vacuum gage working together than I ever learned in years of doing without.

If your trying to work on the idle and cruise the distributor and carb are integrated. Post your combination specs here and I am sure you will get information that will help.

The wideband O2 was the best tool I ever bought because I learned a lot about what was going on in the engine. People who say they can read plugs are pulling your leg. Between changes in how plugs are made, street gas and testing conditions it is BS.

Happy tuning!
 
Mike -
I've done quite a bit of Holley and BG tuning work using an LM-1 Wideband. Just a couple of notes you may find useful:

I always set the carbs up for WOT first. This determines main jet sizing, and I run an 8-jet split between primary and secondary if there is no secondary power valve. Once you get the WOT mixture in the 12.5 - 13:1 range with an 8-jet split you can start looking at the cruise mixture.

On both Holley and BG, the car tends to run at cruise with such a small throttle opening that the majority of the fuel is actually coming through the transition and idle circuits - not through the main metering circuit. You can tune these circuits with no permanent modifications by playing with the Idle Fuel Restrictor (IFR) sizing in the metering block. I've actually found that you can lean the cruise out effectively by inserting a common office staple (which is about .017" in diameter) into each IFR and capture the staple with a 90-degree bend (which the staple already has) under the metering block gasket.

Of course, if your carb has removable low speed air bleeds you should tune with these, but the staple works pretty good for some rudimentary lean-tuning of the cruise mixture.

It's a fun process - hope you have good success!

Lars
 
lars said:
Mike -
I've done quite a bit of Holley and BG tuning work using an LM-1 Wideband. Just a couple of notes you may find useful:

I always set the carbs up for WOT first. This determines main jet sizing, and I run an 8-jet split between primary and secondary if there is no secondary power valve. Once you get the WOT mixture in the 12.5 - 13:1 range with an 8-jet split you can start looking at the cruise mixture.

On both Holley and BG, the car tends to run at cruise with such a small throttle opening that the majority of the fuel is actually coming through the transition and idle circuits - not through the main metering circuit. You can tune these circuits with no permanent modifications by playing with the Idle Fuel Restrictor (IFR) sizing in the metering block. I've actually found that you can lean the cruise out effectively by inserting a common office staple (which is about .017" in diameter) into each IFR and capture the staple with a 90-degree bend (which the staple already has) under the metering block gasket.

Of course, if your carb has removable low speed air bleeds you should tune with these, but the staple works pretty good for some rudimentary lean-tuning of the cruise mixture.

It's a fun process - hope you have good success!

Lars
Click to expand...

I appreciate the input. I've got an LM-1 that's been gathering dust while I've been working on the suspension projects, but I'm looking forward to a change of pace, and doing some tweaks on the fuel system. Once I get the O2 fitting in the pipe and get some data and results, I expect to have a bunch of questions.
Thanks again!
Mike
 
Whatever you do, do not put the lambda sensor too close to the head, those things have their own heater element. Better have it too far back than too far forward, it will ruin your sensor quickly if it gets too hot.
 
Twin_Turbo said:
Whatever you do, do not put the lambda sensor too close to the head, those things have their own heater element. Better have it too far back than too far forward, it will ruin your sensor quickly if it gets too hot.
Click to expand...

INteresting, I used to have my 'normal' O2 sensor, unheated, up at the old heat riser flapper with the rams' horn ...long time ago...now it's heated and on the header collector....

are the Lambda W/B more sensitive to heat??:crutches:
 
yes, they don't like temps above 1650F and ideally should be kept under 1400.
 
Twin_Turbo said:
yes, they don't like temps above 1650F and ideally should be kept under 1400.
Click to expand...

EHH, OK, good information to know....so what is a good location?? for say a 80 mph freeway blast??

some day I want to get one of those tricks, and go play...

:shocking:
 
Twin_Turbo said:
after the collector somewhere.
Click to expand...

Should it go in the header at the collector or can it go just behind the header? Running coated headers and don't want to grind off the coating if I don't have to, would rather put it in the pipe right behind the header.
 
I run my LM-1 bung right after the header collector and this works well.

Lars
 
Also take a lot of notes about your current settings. You can always un-do or back up if you go awry.
 
Lars, I agree with your starting guide!

But I would like to have your opinon on my experience:

In my C3 I have a 427 SBC with 227cc CNC Heads...... of course only to let you have an idea of my engine.
I run a Solid Roller camshaft from Crane, with close to 0.7" of lift to the valves and 265-264° @ 0.050" LSA of 108°

In my engine I found that my Mighty Demon 850CFM Annulardischarge carburetor need a much smaller gap in the front/rear jets.

Of course the engine needs a lot of gasoline at cruise (ok..... below 3000 rpm) because of it's large overlap..... but 4 points looks ok for you?

Advance is some 22° at idle and 34° at WOT....... and can tolerate even 4 degrees of vacuum correlate advance with good gasolines! (..... here in Italy no more that 99 RON+MON/2 octanes).

Opinions?
 
It would be odd for the carb to produce good air/fuel mixture distribution with only a 4-size spread from primary to secondary. Reason for this is that the Power Valve, when open (which is at WOT) is equivalent to 8 jet sizes. In other words, when the carb is at WOT with an open power valve, the fuel flowing through the primary side is equivalent to the jet size plus 8. The idea is to create the same mixture on the secondary side, thus the 8-size increase on a carb that does not have a secondary power valve. If you have a 4-size split, the secondary side will be leaner than the primary side at WOT, making the rear cylinders leaner than the front.

Lars
 
In fact this is my concern!

I opted for a "Neanderthalian Tech" system to solve my problem...... a small piece of copper wire in the two holes of the Powervalve.

The car drives very nicely..... but I can't live with this thing!

I would like to know if you never seen similar problems and if there is somewhere a special Powervelve or a special fuel block with smaller power passages.

Ideas?

Thanks...
 
Give me a few pieces of info if you would:

What's your current jetting primary/secondary?
Which power valve are you running?
How many inches of manifold vacuum are you pulling at idle and at light throttle cruise?
How much of the transition slot on the primary side is exposed at idle?

Lars
 
Last edited:
For the jetting I need to check (i will do it tomorrow morning).... but I guess they are 85/89

I use a power valve of 4,5" and I have some 8-9" of vacuum at idle (i'm quite proud of how my car idles with this cam...... some steady 900 RPM after only a few minutes of warming up)
Of course the vacuum rises at 15" in cruise ( I can drive at 2000 RPM in fifth gear @ 125Km/h)

The transition slot was the harder part of the tuning....... I really was trying to keep only a very small portion opened at idle and playing with advance and balancing between fron and rear throttles.

Basically my opinion is that my engine need very little power enrichening.

I have a wideband fixed in the car and the readiungs are some 12-13:1 @ idle......... 13-14:1 @ cruise.................... and 11-11.5:1 @ WOT.

The car feel really ok....... but I can't reach this result with 8 points gap between front and rear jet !!!

Thanks
Pier Paolo
 
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