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Old 05-20-2006, 08:55 PM
72NOVA454
 
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Runs Like Crap With Air Cleaner On - why?

when I put the air cleaner on (new 14" x 3" air cleaner) it runs like crap at wide open throttle and "sputters". when I take the air cleaner off and road test her, she tears up the road, smokes the tires and gets rubber when shifting gears - no "sputtering".

It's a vacuum secondary carb - just rebuilt Holley 750 with added secondary metering block instead of metering plate.

UPDATE 1: It's not the secondaries. I disabled them so they won't open, road tested again with the air cleaner on (running only the primaries) and same problem. "sputtering" at wide open throttle. So to recap, with only the primaries operational, and the air cleaner on, the engine runs like crap at WOT. when the air cleaner is off, she runs great. I give up. HELP!!!!

UPDATE 2: New update. I road tested again. left the air cleaner assembly on and cut away about 25% of the filter element. It still ran like crap at WOT. I removed the entire air cleaner assembly. She ran great. Next I left the air cleaner baseplate installed (and secured it in place) and left the filter element and top lid of the air cleaner off then road tested. She ran great. so it's nothing to do with the air cleaner baseplate obstructing anything. It's simply to restrictive and it "redirects" the airflow into the venturi's from the side rather than from the top (when the lid is in place). Very unusual. All this might be cause because the secondaries are not opening under WOT? I ordered a new spring kit for the vacuum diaphram and will install a lighter spring and then roadtest it again with the air cleaner off, and then on again.

Any suggestions?

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Last edited by leejoy; 05-27-2006 at 09:51 AM.
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Old 05-20-2006, 08:57 PM
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Linkage hitting the air cleaner?
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Old 05-20-2006, 09:02 PM
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Quote:
Originally Posted by red_rider52
Linkage hitting the air cleaner?
no - I checked. looks ok. I don't feel anything hitting it when I'm driving it. I checked it pretty good when it was parked and sitting still. I'll check it again.

One thing I didnt do is actuate the throttle when the car is sitting still - parked and the air cleaner nut is loosened. if it's hitting the linkage that's when it would be noticeable. I'll try that. unfortuneately everytime I stroke the throttle it dumps fuel into the intake manifold form the shooters.
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Old 05-20-2006, 09:09 PM
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Quote:
Originally Posted by leejoy
no - I checked. looks ok. I don't feel anything hitting it when I'm driving it. I checked it pretty good when it was parked and sitting still. I'll check it again.

One thing I didnt do is actuate the throttle when the car is sitting still - parked and the air cleaner nut is loosened. if it's hitting the linkage that's when it would be noticeable. I'll try that. unfortuneately everytime I stroke the throttle it dumps fuel into the intake manifold form the shooters.
A few pumps isn't going to hurt it.

check to see if the air filter lid is getting too close to the tops of the bowl vent tubes that stick straight up. If there is insufficient clearance, we used to cut the tubes to a 45* angle (High sides to the rear) to give them more air or drill a 3/16 hole on the front side near the top of the tube. What happens is that the air rushing past causes a vacuum around the tubes and sucks a vacuum on the float bowls.....

Rather than modify the carb.....If it will fit, use a 4 inch tall air filter.
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Old 05-20-2006, 10:15 PM
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Doc here,

I had one with a brand new Edelbrock Air-cleaner installed, and It did the exact same thing..

Turns out under inspection, the tube for the breather on the bottom of the Air cleaner, when tightened sat very nicely into the choke linkage and jammed it..

All needed to d to rectify the problem was turn it a 1/4 turn and bolt it back down..

You might want to look..

Doc
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Old 05-20-2006, 10:24 PM
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I have seen people over oil K&Ns and choke the engine.
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Old 05-21-2006, 05:30 AM
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Quote:
Originally Posted by weirdbeard
I have seen people over oil K&Ns and choke the engine.
no oil on my filter element - it is sparkling clean new.
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Old 05-21-2006, 05:33 AM
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Quote:
Originally Posted by xntrik
A few pumps isn't going to hurt it.

check to see if the air filter lid is getting too close to the tops of the bowl vent tubes that stick straight up. If there is insufficient clearance, we used to cut the tubes to a 45* angle (High sides to the rear) to give them more air or drill a 3/16 hole on the front side near the top of the tube. What happens is that the air rushing past causes a vacuum around the tubes and sucks a vacuum on the float bowls.....

Rather than modify the carb.....If it will fit, use a 4 inch tall air filter.
holy smokes.................you might be onto something. If you're right, I'm buying you lunch and a beer. I'll go look at it now, but I thought both bowls (front and rear) have the same vent opening on my Holley model 4160. It seems like it's a secondary issue not a primary - but I will go look.
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Old 05-21-2006, 05:35 AM
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Quote:
Originally Posted by docvette
Doc here,

I had one with a brand new Edelbrock Air-cleaner installed, and It did the exact same thing..

Turns out under inspection, the tube for the breather on the bottom of the Air cleaner, when tightened sat very nicely into the choke linkage and jammed it..

All needed to d to rectify the problem was turn it a 1/4 turn and bolt it back down..

You might want to look..

Doc
I'll check again, but i dont have a choke - I took it off, so that's not the problem, but it might be choking one of the bowl vents like the other reply said.
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Old 05-21-2006, 10:03 AM
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Quote:
Originally Posted by leejoy
holy smokes.................you might be onto something. If you're right, I'm buying you lunch and a beer. I'll go look at it now, but I thought both bowls (front and rear) have the same vent opening on my Holley model 4160. It seems like it's a secondary issue not a primary - but I will go look.
no - that's not the problem. both bowl vents arent even close to the air cleaner housing. Oh well - onto the next theorem.
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Old 05-21-2006, 09:15 PM
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over tightening the nut ?

maybe you can put the lid and base on without the filter ?
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Old 05-22-2006, 05:05 AM
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Quote:
Originally Posted by Vortech 4.3
over tightening the nut ?

maybe you can put the lid and base on without the filter ?
I was thinking the same thing, but why would that cause a problem? both bowl vents are nowhere near the air cleaner housing - plenty of clearance. My next step in figuring this out is disabling the secondary throttles from opening, leaving the air cleaner assembly and filter on, and road testing again just using the primaries. I'm thinking it's the secondaries starting to open that's causing the sputtering. If the sputtering goes away at WOT, its' definitely something with the secondary circuit and I will have to rebuild the carb again. If it still sputters, it's something still with the air cleaner.

Lee
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Old 05-23-2006, 08:27 PM
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to any of you following this thread. I road tested again today with more interesting results. I disabled the secondaries and road tested with the air cleaner on. Ran like crap again at wide open throttle. removed the air cleaner and she ran great. so it's not a "secondaries" issue. It happens when running only on the primaries. for some reason when that air cleaner is installed she runs like crap at WOT. what the heck is going on?

Lee
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Old 05-24-2006, 05:10 AM
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If it's a stock type filter try another brand. Instead of a K&N check out the AMSOIL foam filters. I like them better -- they seem to breathe at least as good as a K&N and you can't ruin them by getting the wrong oil on, they use motor oil. Easier to clean too -- no special kit or fluids to buy.

Sounds like you need to adjust the carb with the air filter on. It should be running a bit richer with the restriction of the air filter. I bet the carb was set up without a filter and that's exactly what's happening now -- it's way rich at WOT. A low restriction filter (like the AMSOIL or a K&N) might fix it right up.

No, I'm not an AMSOIL dealer, but got a filter from a dealer friend to try and noticed the difference right away! That was after a K&N was ruined by spilling motor oil on it. You can't clean a K&N once it gets a petroleum based oil on it. It stops up at the area the dino oil contacted it just as if you stuck a piece of sheet metal over it.
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Old 05-25-2006, 08:48 PM
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I'm still having problems with this. I will roadtest the car again this weekend. My next trick is to put the air cleaner on but cut away about half of the paper element and then run it again to see what happens. I don't know what else to do at this point.

Lee
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