GLENAMY 242SS

iTrader: (1)

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.

SB

iTrader: (1)

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 ?

GLENAMY 242SS

iTrader: (1)

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.

ezstriper

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..

Mr Maine

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

GLENAMY 242SS

iTrader: (1)

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

Mr Maine

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

Baja Rooster

iTrader: (1)

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.

MILD THUNDER

iTrader: (3)

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.

GLENAMY 242SS

iTrader: (1)

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.