AFR Carb adjust question
 

AFR Carb adjust question
454, 8.6:1 Holley 800 cfm dual plane manifold. Mild build full roller motor. Boat idles 11.4 Runs 13.6/13.8 up to 3600 rpm. After that up to about 4000 rpm AFR reading 14.9 / 15.2.
All this is on primaries only. Just at the edge of secondary opening. Pri jets 78, Sec jets 87 single power valve 6.5.
I am thinking that 15.2 is lean. Any idea how to richen the 3600-4000 rpm and not over richen the 2500-3600 area?
Any help appreciated. Thank you.

You can get to 4000rpm on the primaries only ? You sure ? (asking to make sure) what's your method to make sure of this ?
Have you taken any vac readings at any sort of rpm intervals by any chance ?

Yea I thought that was pretty good. Of course I hit the secondaries to get on plane then back down. I marked my throttle with a strip of tape to secondary start. I will recheck that marking tomorrow. I need to take vac reading next outing at the various rpms. Idle (700-800) is at 12-14" vac.

when you jet up you need to go equally ft and rear, how new is the carb ? richening the power valve channels might be the ticket, or try a power valve that opens sooner, may also fix it. i have a blow thru setup act the same, using a quickfuel carb, they had me richen the power valve channels and dialed it right in..

It should start to go lean until the power valve opens and then richen up some. With those jets and pv it shouldnt be that lean, should be in the 12s. I suspect something is up with the carb or fuel distribution with the dual plane

The carb is fresh rebuilt HP500 model w/mechanical secondaries. The motor is also fresh rebuild and I am trying to dial it in.

At 15.2 i'm surprised its not lean backfiring through the carb, that is too lean. For some reason its not pulling the fuel through those jets. For a comparison my friends 454 that dynoed 496hp runs high 12s where you are at with 76/87s and 6.5pv. My experience with old 800 holleys is they arent real consistent. Never knew it though before i had an o2 sensor

That all sounds very lean. I figured for a boat 13.5 or so would be as lean as one would want. I shoot for the upper 12s myself.

Typically, max power on gasoline is 12.5:1 .

That is pretty lean.

Make sure your float level is good, and if you have a .097 needle and seat, throw it in the trash. Float level can play a big part in fuel delivery/mixture.

Check the power valve restrictions, make sure they are not plugged up with dirt/debris. Compressed air with one of those little needle attachments works great. Holleys cheapy power valves suck. Quick Fuels are much nicer, flow more, and more consistent.

Mild, thank you for the ideas. What size needle and seats should I be using? I did not know they made choices until now. I am using the standard one that came in rebuild kit so I am pretty sure it is the .097.
Regarding the power valve I have cleaned the passageways like you have suggested. I saw the Quick Fuel High Flow power valves today and was thinking of trying one of them do you think they make a diff? What is the difference when they talk of a "Single Stage" power valve?
I really need to get this sorted so any/all ideas are welcome. Thanks all.

What horsepower are you at? Heads and stuff? Are you out flowing the capability of an 800 holley? I dont think you should have to totally reconfigure an 800 holley to run it on most 454s

that is a old 800 carb(if oem 500hp) and was set to run on a single plane intake, you can try richening it up see where it goes, but you would be much better off with a quickfuel or a newer holley HP carb, far more tunability.

Yes old HP500 carb (# 9022). Just confused how it can be in the 13's until 3600 rpm then fall to 15's by 4000 rpm.
Mr. Maine, did not dyno motor but nothing special just tried to match parts for strong 5400 rpm motor. 781 heads with 2.19 intake 1.88 ex. ported, air gap (Hardin) dual plane, Holly 800, stainless exhaust, full roller short duration higher lift cam 112 LSA to enhance my 8.6:1 static flat top pistons. It does sound and pull nice so far.
Going to try larger needle/seat and high flow power valve and monitor vac on next run. I just can not see how I can be over powering a 800 cfm carb. How could I tell, besides swapping?
Any help welcome. Thanks all.

It almost sounds like the power valve isnt opening. What is your afr at wide open?

Actually, just breaking it in "The Old Fashion Way" No WOT pulls yet. only 4 hrs on the water. Trying to get everything right down lower first. 4000/4200 is max rpm running under load. @ 4000 throttles indicate primaries only. I have given it quick bursts to 5200-5300 and chopped throttles after a couple of seconds. It gets to 5200 almost instantly with 23 mirage prop. I want to get this lean problem resolved then tackle WOT.

Also, try a one inch open spacer if the dual plane divider goes all the way to the bottom of the carb. Some do some dont.

How will this help with my problem?

The divider can affect fuel distribution, not saying its your issue but the spacer is something to try. Some mainfolds have the divider milled down a bit, including the edelbrock aur gap i believe.

Have you made sure all the passages are clean, power valve, air bleeds, transfer slots ect?

Yes I blew all with carb cleaner then compressed air thru a small needle. Just ordered a set of .150 needle and seats and 4 door high flow 6.5 power valve from Holley.
I will re blow all passageways when I install Power Valve. Also ordered #80 jets just in case but that seems like a LOT of jet!
Still looking for more ideas/suggestions.

It sounds like you just need the fuel curve adjusted. Do you know what size and how many emulsion bleeds you have?

its not the power valve itself, but the channels that flow the fuel when it opens, the 4 window probably wont due a thing, or the larger needle/seats, if you look at the small holes under the valve you will understand, no matter how much the PV will flow still has to go thru these...this one area they worked on with the newer carbs

I understand the New Better Improved aspect of carbs, however, nobody has said "That is a known area of concern with that carb" so I must have something causing this problem. I am trying not to just Pig Fatten the lower rpm to compensate. I'll install the $40 parts, put on a big vac. gauge and try again.
There must be something I am missing, I am far from knowledgable about carb tuning so all help is welcome.

Was this carb running OK and just started acting up or is this a new set up?

New set-up no history on anything. New rebuilt motor new rebuilt carb new rebuilt everything. 4 hrs total water time.

I think 11.4 afr at idle is rich. How much of the transfer slot do you have showing on the primary side? Should be about .020.