So, i switched from my bolt on cowl hood with a 4" filter with a 1.25" drop base, and 1" spacer back to the GTA hood my car came with with a 3" filter with a 1.5" drop base, and no spacer. The air lid is maybe 1.25" above the carb probably only 1".

The car had awesome driveablitiy before, not it kinda has light throttle hesitations, and when quickly getting into the throttle the car will lean spike and then pick up.

Any one have this issue when you reduce the amount of room for the air to turn to get into the carb?

I use a wideband on the car at all times from when the car was going to be sprayed, and the A/F does not change when it has deadspots in the pedal, it acts like the pedal never moved.

The lean spike is confirmed on the wideband, as it will jump to 20-22:1, before it would go to about 13:1 with the cowl hood, im sure that can be tuned out.

Anyone think adding one of the K&N filtered tops might help to bring air strait down? The carb is a 750 Holley HP DP.

 

Found a K&N extreme velocity air filter top, put it on the car, and it ran better at part throttle.

 

do you have a choke horn?

Im running the same carb, and same filter applications. But i dont think it would make the car act as youre describing just because of the air filter.

The air cleaner LID is also important. Some of them "dome" up like mine, others are flat across.

If i lay a ruler across the top of my fiter, it JUST touches the choke plate. However, the "dome" compensates for this.

I also just switched from a 4" filter to a 3" in a GTA hood, and i havent noticed probs like this. However, my car has alot of tuning issues, and inconsistancies, so im not the best person to make that comment.

I find it odd that its a LEAN spike when you reduce the filter size......

 

I can explain the lean spike by the air not being able to turn effeciently enough to get velocity up to draw out fuel well enough.

I also found that my accel pump is worn, and that it was not squirting for the first 10% throttle applied. I corrected the issue, and put the regular solid lid back on (its a dome as well) and it still did it, but not as bad, put the xtream flow back on and it cleared back up.

Im running an HP series carb with out the choke horn.

 

Try adding a Edelbrock 1/2" air cleaner ring spacer to move the whole aircleaner up by 1/2". If you have the hood clearance.
If the bowl vent tubes are very close to the lid trim the top off at a 30deg angle.

 

Ya the hood clearance is the issue, the stud/filter top is already on the bottom of the hood

 

I tried the Edelbrock triangle open air on my stock LG4 back in the early 90's. It ran like ****. It got even worse once I was on the freeway. Sounded cool in the driveway though.
It felt like the turbulance of air at speed under the hood was washing away the fuel flow.
I still had the factory fire blanket on the hood. It doesn't soak up fluid very well, so I put a coule of blue shop towels between it and the air cleaner, and guess what I found.
The rags were soaking in fuel.
I made a small diffuser ring to go around the front half of the filter and squared off the rear towards the cowl, it helped but I ended up going back to the stock air cleaner.
I wonder if your experiencing something similar.

 

wow thats pretty wierd. I heard something once at the track from and older racer, that if you remove your inner fender's (plastic things) that the air flowing through there now will suck the fuel out of the fuel bowls.

 

This is some wierd stuff. I hope mine isnt doing this. I absolutely have NO clearance left if i want to run a stock hood, because im also running Edelbrock's RPM series intake. And because of the DP holley, i HAVE to run the 1/4" spacer to be able to use the rear vacuum port (a must for me).

To get it to all fit, i had to cut away the frame on the inside of the hood around the air cleaner.