WOT Acceleration Issue

[dmrice]

I have a weber 38/38 carb which I seems to be jetted properly through the rpm range according to my wb02 meter. It runs great under normal driving but I am having an issue on WOT acceleration where it does fine for about 10 seconds and then it seems to run out of gas (literally) according to the wb02 meter. The fuel pump seems to be ok (it did the same thing with the old one and the new one I put on recently). Could this be a float level issue? The carb is only about 3 months old and it seems to have been doing this ever since I got it. Any suggestions?

[02Les]

What's WOT?

I'm not learned with all these abbreviations.

[wess02]

Wide OPEN Throttle

[02Les]

Wide OPEN Throttle

Thanks.

I need to write all these abbrs down.

[allbim]

Sounds like the float-bowl slowly empties at WOT. Either your fuel pump is weak or your filter or fuel lines are to restrictive. I'd start with the filter if you have one.

Edit: Just read your post again. Forget the fuel pump.

[dmrice]

I did replace the fuel filter albeit with the same type. Perhaps the plastic bosch filter is under sized. I did cut off the small ends and put larger tubing on the larger part next to the filter body with the same results. Maybe the filter itself is too restrictive. Any recommendations for filters?

[c.d.iesel]

it's not the filter

know what your float level is / should be, and actually

measure it FIRST (Pierce Manifolds shows you

how on their web site)

ignition timing - with a strobe light - and know if the advance is really

working SECOND

NOW ONTO THE 'MAIN' AND 'AIR CORRECTION' JETS -

state for the class what size jets you have now

[allbim]

Sorry, c.d., I agree with most of what you say, most of the time. But dmrice clearly says that his O2 meter indicates that the mixture leans out after 10 seconds of WOT. I don’t see how that could have anything to do with ignition timing. I also don’t see how an incorrect float level would cause the fuel level in the float bowl to slowly drop. I am wondering if the float valve itself is too restrictive, due to some manufacturing defect. I would keep looking for anything that restricts fuel flow.

[TobyB]

fine for about 10 seconds and then it seems to run out of gas (literally) according to the wb02 meter

Do that, then switch off, roll to the side of the road, and open the top

of the carb. You'll most likely find it dry.

It's a fuel supply issue.

Tank intake clean? Line clear?

(I think the stock line is very marginally sized for anything over stock)

Air leak at the tank, filter, or anywhere else in the suction side?

Air in the filter? It acts as an airspring and reduces pump efficiency...

try putting it on the pressure side...

Wrong/too short pushrod? Partially clogged filter in the carb?

Too small needle valve?

... there's gotta be more, but that's what I got so far...

This might be one reason to go to a pusher pump by the tank, if everything

else is OK.

My street car has this problem at the track occasionally- I have to bleed all

the air out of the fuel filter, then make sure it doesn't suck air during the

day. I really should fit a screeen to the pickup and move the filter to

the pressure side...

hth

t

[dmrice]

Just for the record - Filter on pumping side, 57 idles, 150 mains, 185 ac (stock - I haven't tuned the ac's). A/F mixture on idles is around 12 and 13.5 on mains. And to restate, car accelerates great with no hesitations for about 10 seconds and then A/F goes to max. lean., I have to back off on the accelerator (I assume to let the float bowl fill back up) and then all returns to normal as I stay at cruising speed (this typically happens when I am getting on the entrance ramp of the freeway - if I moderately accelerate, all is well, but if I floor it then I get the issue). Has anyone tried using the return line as the supply instead? I thought about that just as an alternate to see if the main supply line was an issue.

[TobyB]

150 mains,

holy hose pipe, if you didn't have air/fuel I'd say you were running huge rich...

Yah, the return pipe's both bigger AND metal, isn't it...

t

[dmrice]

25mpg on the highway - I do have o2again headers and IE exhaust so maybe that affects the jet size.