how much air does an engine need?

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Guy Johnson

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Nov 10, 2025, 10:05:03 AM (2 days ago) Nov 10
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Engines are basically air pumps. 
An Atomic 4 with 64 cu in displacement running at 2,000 rpm will need 128,000 cu inches of air per minute. Divide by 1,728 to get 74 CFM. Engines need a lot of air for combustion and then some extra to cool your alternator and other bits that tend to heat up. 

Guy
Puffin 10M #6


James Keszenheimer

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Nov 10, 2025, 10:51:24 AM (2 days ago) Nov 10
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good insight Guy! So putting an intake fan in that quarter berth opening might be better than sealing it off.
Jim


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Dave Cole

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Nov 10, 2025, 11:05:47 AM (2 days ago) Nov 10
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Just leave it open.  The engine will pull the air in just fine.  
I removed the cabinet panel in front of my engine.  There is no way to maintain and check the engine with the panel in place.
My panel was screwed in place.

Dave
10M #26

James Keszenheimer

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Nov 10, 2025, 11:42:17 AM (2 days ago) Nov 10
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ya, my door doesn’t latch so it’s always open during use and I removed the under sink drawer because of always hitting my head on the wood brackets while under the sink. It still gets pretty hot under there…and smokey in the cabin, but that’s the other story...
Jim



Guy Johnson

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Nov 10, 2025, 11:43:17 AM (2 days ago) Nov 10
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I've kept my engine panels in place, but I did make them easier to remove. I used rivnuts to make permanent threaded holes in the cabinets and fiberglass attachment points. No more dealing with stripped wood screws. 
Here's an example of the fasteners I'm talking about. They come in a wide range of materials and designs. 


Guy

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Subject: Re: [pearson ] how much air does an engine need?
 

Guy Johnson

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Nov 10, 2025, 11:45:29 AM (2 days ago) Nov 10
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Jim, I don't remember which engine you have. I added the PCV kit to my atomic 4 and it does a much better job of containing the blow-by then the old rubber hose did. 

Guy

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Subject: Re: [pearson ] how much air does an engine need?

James Keszenheimer

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Nov 10, 2025, 11:49:16 AM (2 days ago) Nov 10
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Ooh, I like that idea. I can use that for my bimini tubes. I was using sheet metal screws instead of rivets so I could take it apart but they don’t thread in well.

Guy, do the rivets hold well in the fiberglass without rotating? Do they bend around the back surface like a regular rivet?
JIm




Jim Keszenheimer

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Nov 10, 2025, 12:06:38 PM (2 days ago) Nov 10
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Yup A4 here too. I was wondering if that kit was worth doing. I might try that. Thanks for the info!

On Nov 10, 2025, at 11:45 AM, Guy Johnson <guy...@hotmail.com> wrote:



Guy Johnson

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Nov 10, 2025, 12:10:01 PM (2 days ago) Nov 10
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1

I also found some with 4 'legs' like a toggle bolt. 
Guy

Ooh, I like that idea. I can use that for my bimini tubes. I was using sheet metal screws instead of rivets so I could take it apart but they don’t thread in well.

Guy, do the rivets hold well in the fiberglass without rotating? Do they bend around the back surface like a regular rivet?
JIm




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Guy Johnson

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4:19 PM (2 hours ago) 4:19 PM
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