got the car on the chassis dyno.

on a slightly different subject, in line with another thread that i had posted on my oil consumption, with a pressure gauge on the dipstick the gauge was fluttering between 1/2 and 1 psi of pressure when the engine got in the upper rpm range WOT.

on my first pull the A/F on WOT was sitting at mid 14's. perfect, i thought. i knew i was running lean, and i had the biggest step on the power step of the metering rods, and 3 steps to go down. i figured i could get this close with 2 steps, and certainly get it there with all 3. that's a <5 minute change as opposed to 30 minutes to change jets.

in my experience with the carters/eddies, 1 jet is worth approx. 1 point in A/F when in this range. and 1 .005 metering rod step is worth about 2/3 of a jet size.

so i went down 2 steps, and ran it again. virtually no change in the A/F.

???

so i looked around at everything i could, which really isn't much without tearing into things, but this just didn't make any sense. i decided to at least verify that, and went up one jet on my secondaries, and back to the original rods. this should have virtually cancelled out my original metering rod change, but still given me much richer readings than my original run.

but still, the A/F was the same.

then i went down the same 2 steps, and picked up a little HP and torque, but the A/F numbers were pretty much the same.

the O2 sensor was in a bung in the header, so is as accurate as can be from that point of view. i have yet to run into a situation where a jet or major metering rod change had no effect.

i tested my fuel pump a while ago, and it had a steady 5-6 psi, (i forget exactly where it was). and it doesn't show that at some point it is starving for fuel, in that it isn't rich for a while and then falls off. when he jumps on it, it is in the 12's, then there is 1/2 a second to a second where it is up in the 15's, and then settles for the rest of the run into the mid to low 14's.

i'm going to put a tee in my fuel line and test my pump pressure at WOT to eliminate that, but other than that, i can't think of anything that would cause a major jet change to have no seeming effect on A/F.

again, ???

Silly question but... open headers or thru the exhaust?

Kevin

Is this on dual quad hemi in your sig?

IMO, changing just the rods on the primaries of both carbs (I presume) would not effect a very large change in the WOT a/f.

If the light load cruise a/f is lean.
I would go up at least one jet size in all eight holes.

If light load cruise is fine, I would richen the high speed step in the primary rods, and jet up one maybe two sizes on the secondary jets.

I tune with metering rods on the dyno also because it is so much faster. As long as you are using metering rods that have the same large step diameter and a smaller second step you should be going in the right direction. For example, start off with 65/52 and go to 65/47 and then to 65/42 rods.

The other thing is to measure the rods to make sure they are actually what you think they are. I always use a dial caliper to double check the rods.

Lack of fuel flow can be causing the issue that you are seeing. Either the fuel pump isn't putting out enough volume or your needle and seats are at capacity. Have you installed the larger needle and seats?

one thing more to do before you change to larger needle and seat is to jump up to like a .113 jet and see if your a/f changes,if not, then go to the larger needle and seat think it .120 and then if that doesnt work,look for vacuum leak or you need a larger fuel system.

I realize it should have changed some, but, have you calibrated or changed the sensor recently?

sensors will work then show no reading, when they are done from my experience.

with afb's prmaries should be richer than secondaries.
but in large stroker motors i usually run square in all 8.
go bigger on your primaries.

Have you looked at the plugs after a pull?