Re: [Amc-list] LPG 258

[Matt Haas <mhaas@xxxxxxx>]

So what you are saying is that the cylinder pressure is higher because 
you can get more air into the cylinder to compress, correct? I honestly 
do understand that and it's why turbo and super chargers make more power 
  but you still haven't altered the size of the cylinder so the 
compression ratio hasn't changed.

Matt

On 10/7/2008 11:24 AM, Jim Blair spouted this sage advice:
> While you aren't changing the static compression, you are increasing the efficiency of the motor to draw that in which is what increases it's potential and at the same time, if you pumped the motor before and after a 4.0L head swap, the compression would be slightly higher. The port and intake restriction of the 4.2L creates a blockage.
> 
> Jim Blair, Lynnwood, WA '87 Comanche, '83 Jeep J10, '84 Jeep J10
> From: Matt Haas 
> Subject: Re: [Amc-list] LPG 258
> To: "AMC/Rambler owners, drivers and fans." 
> Message-ID: 
> Content-Type: text/plain; charset=ISO-8859-1; format=flowed
>  
> I understand the gains you get from better flow. An engine is basically 
> an air pump so the more air you can move through it, the more potential 
> for power you have. I'm not arguing that the 4.0 head isn't a good swap, 
> just that without changing the cylinder volume, you are not altering the 
> engine's compression ratio.
>  
> Compression ratio is a measurement comparing the cylinder volume with 
> the piston at BDC vs TDC. The only way to change that is to physically 
> alter the size of the cylinder.
>  
> Matt

-- 
mhaas@xxxxxxx
Cincinnati, OH
http://www.mattsoldcars.com
1967 Rambler American wagon
1968 Rambler American sedan
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