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STR8 headers vs stock log exhaust

4K views 17 replies 8 participants last post by  JDubya 
#1 ·
Full SRT8 exhaust really woke up my 09 WK 5.7 Look how restrictive the stock manifolds are. I now run 14.20 @97mph with the above exhaust and predator 93 tune and K+N CAI and 180 stat. Not too shabby for a porky 4400lbs!!
 

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#4 ·
Damn I wish we 4.7 guyz had that option :( ...
 
#5 ·
I am very impressed with the 5.7 hemi. Heads seem to flow very, very well and I want to do more mods to my jeep. I would like to look into the benefits of the srt8 intake compared to the stock 09. And larger throttle body as well. This engine has 10.5-1 compression and has never knocked so I think I may look into a more aggressive CMR tune....... TBF
 
#6 ·
Not shabby at all...
Congrats on getting it running so good.
Is that 14.2 at the track? Impressive!
You might be the first one to dip N/A into the 13s, maybe with a more aggressive CMR tune alone without doing anything else. You are running the 93 CAI canned tune right?
Not sure an SRT8 stock intake would help, a polish/ported one I'm sure it will.
What headers are are you running?
Keep up the good work and keep us posted. Hopefully you'll get into the 13s soon, I'll be in the look-out for that. :thumbsup:
 
#8 ·
Ive done some research, and the 09 intake vs the srt8 intake is very small, something like only 2 cfm more from the SRT.

I'd say do as scott mentioned and look into 09 ported heads. We should find a vendor because i've been wanting 09 heads so I can run SRT headers.

Or get a cam, and tune, and youll be in the 13's with ease
 
#9 ·
I will probably do the heads a bit down the road and a cam for sure if I end up pulling the heads. I just emailed Johan about a custom tune as i am pretty sure the diablosport 93tune leaves a bit of power on the table. That plus a set of slicks should get me in the 13,s pretty easily as my 60ft times were 2.2 and this was at bradenton with air temp in the 80,s..... For us 5.7 guys, I would not hesitate to buildup these motors. Not really much difference in engine size (345 vs 370) so only about 30-40hp less for any given combo. 09 and later heads are the ones to use and fully ported probably are pretty close to srt8 heads with the larger chambers. I figure a well built 5.7 motor could make 450-470hp all day long and run on 93 octane. Even with the cast crank/pistons, that power level should not be a factor in reliability if rpm,s are kept around 6K max..... The bottom line here is that the best mod you can make for a 5.7 is to go with a free flowing exhaust and the srt8 setup is just about optimium. That made the most difference for me. Just look at how those stock manifolds choke the flow....... I will get this bitch into the 13,s with just bolt ons for sure..... just might need a cold day to do it! TBF
 
#10 ·
I will probably do the heads a bit down the road and a cam for sure if I end up pulling the heads. I just emailed Johan about a custom tune as i am pretty sure the diablosport 93tune leaves a bit of power on the table. That plus a set of slicks should get me in the 13,s pretty easily as my 60ft times were 2.2 and this was at bradenton with air temp in the 80,s..... For us 5.7 guys, I would not hesitate to buildup these motors. Not really much difference in engine size (345 vs 370) so only about 30-40hp less for any given combo. 09 and later heads are the ones to use and fully ported probably are pretty close to srt8 heads with the larger chambers. I figure a well built 5.7 motor could make 450-470hp all day long and run on 93 octane. Even with the cast crank/pistons, that power level should not be a factor in reliability if rpm,s are kept around 6K max..... The bottom line here is that the best mod you can make for a 5.7 is to go with a free flowing exhaust and the srt8 setup is just about optimium. That made the most difference for me. Just look at how those stock manifolds choke the flow....... I will get this bitch into the 13,s with just bolt ons for sure..... just might need a cold day to do it! TBF
Not following you here bro. How did you end up getting the 30 to 40 hp less?
345 and 370 like you said is the size of the motor not hp, horsepower between the two is 330 hp for the '05 to '08 5.7L and 357 hp for the '09 - '10 5.7L. The SRT8 is 420 hp (as advertised to the crank numbers).
I do agree with you, the 5.7L has so much more to offer and starting with the intake and exhaust areas make a huge difference once you upgrade them. Just look at the LX guys how much they have accomplished out of the 5.7Ls. And now with CMR tuning available for the 5.7L Jeeps, there's so much more you can do to it. I'm surprised no one has gone crazy with a 5.7L jeep as the LX guys had with theirs.
 
#17 ·
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
 
#18 · (Edited)
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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