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  #13  
Old 11-18-2010, 08:05 PM
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Re: STR8 headers vs stock log exhaust

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Originally Posted by QBNKID View Post
Ryan, I know he is talking about the displacement as I mentioned to him above. I just want to know where the 40 hp extra comes from the extra 25 cubes. How do you guys come up with 40? Fill me in...
GENERALLY SPEAKING, Displacement via boring or stroking increases power proportionally . X amount of displacement can yield up to Y amount of power. This magical number is typically around 1.5 HP per cube or so. Again, I stress that I'm being very general and not very specific.

Assuming same compression, cam profile, heads, etc etc. the 6.1 will only be about 40 crank hp ahead of a similiarly equipped 5.7. The 6.1 makes more power out of the box in comparison to the 5.7 because it was set up to do so- the cam profile is slightly more aggressive, the heads are cast differently, the PCM cal is more aggressive, etc. Build each motor with the same heads, same cam, same compression, etc, and the difference between the two respective motors will diminish.
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  #14  
Old 11-18-2010, 11:03 PM
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Re: STR8 headers vs stock log exhaust

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Originally Posted by FlyinRyan View Post
GENERALLY SPEAKING, Displacement via boring or stroking increases power proportionally . X amount of displacement can yield up to Y amount of power. This magical number is typically around 1.5 HP per cube or so. Again, I stress that I'm being very general and not very specific.
Still doesnt make sense to me! If you say 1.5hp per cube...1cube is about 16cc and 1hp is about 16cc then wouldnt 1cube = about 1hp?

Sow how does 25cubes = 40hp?

Maybe Im messing something up here?!
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  #15  
Old 11-19-2010, 02:30 AM
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Re: STR8 headers vs stock log exhaust

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Originally Posted by xoxSTUGOTSxox View Post
Still doesnt make sense to me! If you say 1.5hp per cube...1cube is about 16cc and 1hp is about 16cc then wouldnt 1cube = about 1hp?

Sow how does 25cubes = 40hp?

Maybe Im messing something up here?!
I'm not sure why you're bringing another unit of measurement into it?

I dont understand where you got 1 hp= 16cc? Are you referring to a stock 5.7 making approximately 1 hp per cube?
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  #16  
Old 11-19-2010, 07:20 AM
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Re: STR8 headers vs stock log exhaust

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Originally Posted by FlyinRyan View Post
I'm not sure why you're bringing another unit of measurement into it?

I dont understand where you got 1 hp= 16cc? Are you referring to a stock 5.7 making approximately 1 hp per cube?
Cause how else can you try to estimate it?
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  #17  
Old 11-19-2010, 08:20 AM
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Re: STR8 headers vs stock log exhaust

Hey guys, sorry for the confusion..... I was comparing the 5.7 vs 6.1 assuming both motors built equally. The previous posters said it better than I did, a well built N/A motor should make easily 1hp per CI. My stock 09 does just that with 357HP.After my simple bolt on mods, I am up around 400-410 right now. Even the stock ram trucks are rated at 390hp so getting 1.1-1.2 hp per CI is not hard to do. 25 xtra cubic inches of displacement equates to 30-40hp with a well Built combo...... Our hemi heads flow very well obviously and just letting them breathe is half the battle. I Bought an 06 srt8 cam to install but did not realize I had the VVT and those cams are big bucks. That is what is limiting my combo now as the stock cam is very mild. I need to research some other forums to see what others have done with their 5.7 combos. My main message with this post is the key to getting any decent power from a jeep 5.7 motor is to get some kind of header to replace the crap log manifold.... I ran my jeep up to 140mph easily and it was still pulling good. I,m sure it would top out at 150 plus but I don't have v-rated tires and really don,t care about top end speed. The headers and free flowing exhaust is what really woke up my combo..... TBF
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  #18  
Old 11-21-2010, 12:41 AM
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Re: STR8 headers vs stock log exhaust

I've been thinking about doing this for a while, did they bolt right up or did you have to mod anything? Things like the dip stick, O2 sensors, etc...
edit: never mind, I remember your post in the shorty headers thread... install was a bitch lol

I have a Gibson exhaust so I wonder how well the SRT8 system would perform if merged into one just before the muffler, surely better than the 5.7 headers
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