455

 

Add 6 sizes to the rear and take out 2 in the front, see what that does. A stagger of 8 front to back is about normal for most carbs with only a primary power valve. Beyond that, depending on the year/model of carburetor you have, you may have to change the power valve restriction circuit on the primary side in order to get a better balance there.
Hope this helps.

 

The other thing to check beyond jetting when you have a lean condition at WOT is the rest of the fuel system, is your pump able to keep up?

 

O2 sensor placement and mounting plays a huge role, too. Is it welded in or one of those crap saddles? I wouldn't go off AFR alone. Read the plugs for better accuracy.

 

I am 80 /86 and am very close to my ideal results. Going to play with some side to side stagger jetting as #8 is leaner than the rest.
I live at 3500 feet elevation with hot dry summers, so DA is usually 4500 - 5500.
I will probably end up right where Mark suggested you start.....

 

I've seen about 20 different ways of reading plugs that all contradict each other. Not sure I'd consider that more accurate than an O2 sensor installed properly.

 

Curious as to what could contradict. You're getting a definite result directly from the combustion chamber. I'll admit; it can be a rabbit hole, but the fundamentals apply. You don't need to get crazy and cut the threads off to see the base of the porcelain for a decent read on what's happening.

 

Link for this one, as the text is separate from the photo:
https://fboignition.com/articles/sparkplugreading






All of these say something different about where to read jetting, timing, and heat range. One claims you can read idle, midrange, and WOT jetting off the spark plug whereas others, on this forum even, will say the only way to read a plug at WOT is to shut it down immediately after the pull.

So which is right? And what authority is there to your answer over any of the others? I'm unfortunately coming across more harsh and argumentative than intended here - its just that reading plugs does not seem to have any kind of consensus other than what they look like for VERY bad tunes. So I find it hard to trust this as a meaningful way to diagnose much of anything.

 

I'm not trying to start anything, but every good tuner on the planet will at least look at the plugs. Lean is white to off white as shown in the second pic. The first involves removing the threads. Let's call that the advanced class.
My point is about data collection. The more you have that agrees, the better chance you have of finding the problem. Let's say your AFR gauge is reading lean, as it is, but your plugs are wet and fouled on a couple of cylinders. Are you more likely to believe the gauge or the plugs. Personally, I'll take the plug read.
When I was tuning my idle, I called the Holley tech line, and was told to ignore the AFR and use a vacuum gauge. It makes sense to me. AFR is helpful when doing part throttle stuff. However, if there's a leak around the O2 sensor or it's too close to an opening (open headers), they're pretty well useless.

 

Yes, swapped the red holley 97gph for 140gph at 14 psi with regulator and mounted below and close to the fuel tank.

 

I also was not trying to start anything, just pointing out my frustration with the whole "reading plugs" thing and how many conflicting versions there are of reading them.

We also may be talking about very different applications for an AFR gauge. My car is fuel injected and it is critical to have no leaks around it and plenty of exhaust length behind it. It works perfectly fine at idle, off idle, cruise, and WOT. If you're running open headers, then yeah, it isn't going to work well. Huge cams also can cause issues at idle but smaller cams generally don't. Even then, I can definitely concede that you're only getting an average of one bank. It won't tell you if one cylinder is super rich and another super lean. Again, I think reading plugs is certainly useful for horribly out of tune situations. I just can't buy into fine tuning with them until there's an actual consensus on how to read them.

 

455 - gen 2 edelbrocks - hyd roller - torker
no PV on secondary
Holley 950

 

The transition circuit is pretty rich on the HP, you can try putting restrictors in the transfer slot feeds and see if that gets you where you want. I drilled and tapped the carb body for 10-32 set screws for all 4 transfer slot feeds and then drilled them to ~.080 and that helped get the part throttle cruise closer to where I wanted it. This will affect the tip in though and can cause a stumble if it's too lean.

 

Are you around 425hp?

 

As another reference point, I have an 850HP on a ~450 horsepower 455 and I settled on 80/87 with the rear PV blocked.

 

Great question, At this point I would guess yes.
I have only made 3 1/8 mile passes and that was 10 days ago. No quarter mile passes as that track is 3 hours away.
8.19 @ 87.63 was best
Track was scraped for street night / so no prep at all. 1.9- 60 foot. Tried to modulate throttle and clutch to get max traction in first......
G meter went over one g for split second and then dropped like a rock...Need to go back on test and tune day with prep....
MT ET street bias ply slicks

 

How much air bleed do you have in it?

 

You have an 830 HP. I'm assuming it's a new 80509-2?
If yes your 96 jet without PV is not abnormal. Your going to have to take your time tunning this carburetor as it's most likely not correct for your application. The 830 was designed to fit NASCAR applications that call for a maximum throttle bore of 1.688 that allows unlimited modified venturi. You essentially have an 850 main body on a 750 base plate. What this means is you will have a week signal to the booster unless pulling a large demand. This is part of the reason you need so much jet for WOT. The other reason is the newer aluminum 1.56 main body in general needs more jet due to the venturi design is lacking compared to the older zink castings. Your rich part throttle will need to be corrected through idle air bleed and idle feed restriction. You will need different metering blocks for IFR changes. Your best bet is to get the correct carb for your application.

 

32 for the high rpm air bleeds and 72s for idle

 

How can I tune the venturi to make signal stronger? Currently 32 high rpm air bleeds on all four corners and 72 idle air bleeds.

 

80509-1 zinc

 

That's good it's a dash 1. When you take out the PV you need to jet up from 8 to 10 in most cases. When jetting you want to be usually within 5 jet sizes from factory. You are doing Ok so far, keep working on WOT until you get that. After that you can start on drive ability. If you make too many changes at one time you can get lost real easy.

 

What afr do Olds 455 like leaner or richer? Low 12s,mid 12s or more towards low 13s high 12s for NA power.

 

The brand of engine really doesn't mater. A good place to start is on the richer side, less chance of damage. Mid 12s to start. Work your way leaner until you have your best MPH. Personally I don't like leaner than 12.8 to 13.1. While working your way leaner if it slows up go richer until it falls off then -1 to 2 jet front and back. Every combination is different. As long you are in the 12's you are safe. Periodically check the plugs to make sure you have no issues.