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Old 02-07-2021, 03:43 PM   #1
Asshat
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Loud air sucking noise on acceleration

When I accelerate the noise is really loud. I have the stock air cleaner, so that’s probably not it. I know my exhaust leaks here and there, but it doesn’t sound like exhaust. It idles fine too, so I don’t think it’s a vacuum leak.
Any idea what it could be?
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Old 02-07-2021, 04:17 PM   #2
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Re: Loud air sucking noise on acceleration

Can you get an audio/video of it?
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Old 02-07-2021, 05:48 PM   #3
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Re: Loud air sucking noise on acceleration

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Can you get an audio/video of it?
No, didn’t get a video.
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Old 02-07-2021, 11:59 PM   #4
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Re: Loud air sucking noise on acceleration

I wanna say check timing.
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Old 02-08-2021, 12:09 AM   #5
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Re: Loud air sucking noise on acceleration

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I wanna say check timing.
Timing seems ok, right about 4 degrees BTDC.
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Old 02-08-2021, 12:57 PM   #6
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Re: Loud air sucking noise on acceleration

What engine are you running? Last time I heard something similar to your explanation it was leaking intake gaskets on my V-8
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Old 02-08-2021, 01:10 PM   #7
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Re: Loud air sucking noise on acceleration

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What engine are you running? Last time I heard something similar to your explanation it was leaking intake gaskets on my V-8
Inline 6, 292. One bbl carb, new from Rock Auto.
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Old 02-08-2021, 01:21 PM   #8
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Re: Loud air sucking noise on acceleration

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Inline 6, 292. One bbl carb, new from Rock Auto.
pour a little water around intake gaskets while running and see if engine misses.
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Old 02-08-2021, 01:32 PM   #9
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Re: Loud air sucking noise on acceleration

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pour a little water around intake gaskets while running and see if engine misses.
I did try carburetor cleaner while it was running, nothing changed.
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Old 02-08-2021, 01:42 PM   #10
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Re: Loud air sucking noise on acceleration

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I did try carburetor cleaner while it was running, nothing changed.
Pour water around the intake attached to the head.
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Old 02-08-2021, 03:55 PM   #11
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Re: Loud air sucking noise on acceleration

If you have power brakes it could maybe be the check valve gizmo where the hose connects to the booster but then again, that might be more of a "throttle closed" type leak
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Old 02-08-2021, 04:03 PM   #12
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Re: Loud air sucking noise on acceleration

I have the same engine and carb. I have an open element filter and the intake noise is very noticeable. I suspect you are hearing what engineers have spent years designing out of our newer cars with big plastic air boxes and convoluted intake snorkels.
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Old 02-08-2021, 04:29 PM   #13
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Re: Loud air sucking noise on acceleration

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I have the same engine and carb. I have an open element filter and the intake noise is very noticeable. I suspect you are hearing what engineers have spent years designing out of our newer cars with big plastic air boxes and convoluted intake snorkels.
I have had older vehicles and never experienced this loud of air suck.
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Old 02-08-2021, 06:29 PM   #14
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Re: Loud air sucking noise on acceleration

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Originally Posted by AcampoDave View Post
If you have power brakes it could maybe be the check valve gizmo where the hose connects to the booster but then again, that might be more of a "throttle closed" type leak
No power brakes.
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Old 02-08-2021, 08:37 PM   #15
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Re: Loud air sucking noise on acceleration

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Originally Posted by caseyjones View Post
I have the same engine and carb. I have an open element filter and the intake noise is very noticeable. I suspect you are hearing what engineers have spent years designing out of our newer cars with big plastic air boxes and convoluted intake snorkels.
Same here, even with the stock air cleaner, I have to agree with CaseyJ
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Old 02-08-2021, 08:45 PM   #16
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Re: Loud air sucking noise on acceleration

Has it always done it, or is it a new symptom?
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Old 02-08-2021, 08:46 PM   #17
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Re: Loud air sucking noise on acceleration

fan would be my guess
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Old 02-08-2021, 11:15 PM   #18
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Re: Loud air sucking noise on acceleration

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Has it always done it, or is it a new symptom?
I have only had this truck since April 2019, and I just got it on the road this past week. Most of the time it was up on jackstands in the garage.

I am thinking it could be an exhaust leak; I assembled the entire exhaust from pieces I had in the garage, and a few new ones. I may just take it to an exhaust shop this Saturday and see what they will charge me.

I could pull the air cleaner off and drive it, see is that makes any difference. It sounds good at idle, and once it warms up it accelerates ok.

I have the 4-speed, stock transmission, it shifts fine. The rear end is a 14-bolt GM, 4:10 or 4:11 gears, from my calculations. The truck seems to top-out at about 55mph, primarily cuz it sounds like I am really pushing it, at about 2k rpm (if my tach is correct). It just seems so loud going down the road, but not like exhaust noise. As it is, the muffler I have installed is one of those quiet mufflers.

Brings me to another question... if its worth putting 3:42 gears in it vs a 5-speed OD trans. A ring and pinion will cost about $300, and a 5-speed is probably north of $800.

I think the 3:42 will only drop my rpm by about 500rpm, if I'm not mistaken. I'll have to check some gear tables.
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Old 02-09-2021, 03:22 PM   #19
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Re: Loud air sucking noise on acceleration

I have an appointment at the muffler shop; figured I would get that out of the way, then go from there.
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Old 02-09-2021, 04:27 PM   #20
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Re: Loud air sucking noise on acceleration

I'm thinking you have too much back pressure in the exhaust system. 292 engines have a very restrictive exhaust system. That "quiet" muffler is causing a lot of back pressure. Have them build a system with 2 1/4 or 2 1/2 pipes & a free flow muffler.
4:11 gears are as high as thy come for that rear end. A 5 speed with o-drive would be the way to go.
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Old 02-09-2021, 04:50 PM   #21
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Re: Loud air sucking noise on acceleration

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I'm thinking you have too much back pressure in the exhaust system. 292 engines have a very restrictive exhaust system. That "quiet" muffler is causing a lot of back pressure. Have them build a system with 2 1/4 or 2 1/2 pipes & a free flow muffler.
4:11 gears are as high as thy come for that rear end. A 5 speed with o-drive would be the way to go.
George
I spoke with a gear outfit, they told me the 14-bolt GM can go as high as 3:42.

I’ll check with the muffler shop, see how much they’ll charge.
Not even sure what it should cost.
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Old 02-10-2021, 05:12 PM   #22
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Re: Loud air sucking noise on acceleration

The original rear end in the 3/4-1ton trucks 72 on back had 4:11 gears as the highest ratio available. The 73 up had 3:42 ratio.
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Old 02-10-2021, 05:18 PM   #23
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Re: Loud air sucking noise on acceleration

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The original rear end in the 3/4-1ton trucks 72 on back had 4:11 gears as the highest ratio available. The 73 up had 3:42 ratio.
George
That was for the original HO52/72 rear end; I swapped mine with a later ‘73-up rear end.
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Old 02-11-2021, 07:28 PM   #24
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Re: Loud air sucking noise on acceleration

I don't remember if you have an oil bath air cleaner. If so, make certain that the oil level is where it should be.
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Old 02-11-2021, 09:40 PM   #25
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Re: Loud air sucking noise on acceleration

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I don't remember if you have an oil bath air cleaner. If so, make certain that the oil level is where it should be.
No, regular dry air filter.
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