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HemiX3

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  1. Been there, done that. I'll give you my 2 cents worth FWIW. On a pretty much stock 5.7 (mainly stock rotating assembly), the stock 5.7 heads are more than adequate for the displacement of the engine. Hot Rod Network did dyno tests on a pretty much stock (headers and cam) 5.7 using stock heads and ported/polished heads and the gain was only 12 horsepower. https://www.hotrod.com/articles/hemi-head-test-mild-and-wild/ I've ported/polished and milled .030 in. off the heads on both of my 5.7's and, if I've gained 25 hp., I say I did good. Milling the heads (raises the compression ratio by about a half point) were maybe worth 10-15 hp. and the port/polish was worth about 12 or so hp. You'll see, in the article, that if you increase the engine displacement, the gains will be much more substantial. The same would be true if you kept the stock displacement and went with properly set up forced induction and/or nitrous oxide injection,.Then bigger heads will help. As far as cams go, I would caution you to NOT go with a "large" cam with your stock displacement, pretty much for the same reason. If you go too big, a couple things will happen. First, your bottom end RPM power will be significantly reduced because almost all performance cams sacrifice the low end, in favor of improving the mid and top end RPM ranges. Second, your idle and driveability will be adversely affected, depending on how radical you go. I have advanced FRI Sidewinder cams in both of my 5.7's and, IMO, they are about as radical you'd want to go without having driveability issues for a daily driver. Regarding running nitrous on a stock rotating assembly, you probably wouldn't want to go more than a 75-100 shot, or you'd be at risk of gernading the engine. IMO, this is a good "on call" mod when coupled with a well selected cam, a good tune, headers/cat. back and the transmission set up properly. If you're into drag racing, a 75-100 shot can take about a full second off your elapsed time. One last thing......I would NEVER recommend Total Engine Airflow (TEA) for porting/polishing heads after the experience I had with them. I sent my pristine heads to them and four, yes four months later I received a different set of heads that had obviously been worked on before and were not near as nice as the ones I sent them. They claimed their CNC machine programming screwed mine up. I will say that the port and polish job was very nice though but, I'll never know what really happened to my heads. On my other 5.7, I found a shop locally that ported and polished them. That way I was able to keep an eye on them and what was being done to them.....a completely better experience.
  2. Can't do much with the NAG1, so the easiest thing to do is install a taller gear. The 5.7's came with a 2.82 in lieu of the 3.06 gear that's in your SRT8. It's a pretty easy swap. With the 2.82 gear, your cruise RPM will be about 1800 RPM. I have two early LX's, an 05 5.7 Magnum and an 06 6.1 300C SRT8 like yours, but both with performance cams in them. I am not sure why you want to lose a few hundred RPM though? If you have the stock cam in your 6.1, it is a mid/top end RPM range cam and you'd probably end up losing a little fuel economy. To improve fuel economy, you need to have a good tune and bring the RPM to a range that is as close to the power band as possible. I ended up installing a Getrag 3.06 LSD in my 5.7 and, along with the cam, MDS and other mods. I usually get 27-29 mpg on the highway and 15-17 mpg in town, and the 6.1 with the cam and custom engine/transmission tunes usually gets 23-25 mpg on the highway and 13-15 mpg around town. When the stock cam is compared to the performance cam in my 6.1, the biggest difference in the timing between the two is the Lobe Separation Angle (LSA). With a higher LSA, the power band is raised to a higher RPM, and vice versa. The stock 6.1 cam has an LSA of 117* and the aftermarket cam in nine has an LSA of 113* so mine performs substantially better at lower RPM than when it was stock and not quite as good at higher RPM.....where i't seldom driven.
  3. I know the answer to your question but, with your attitude, I certainly won't give it to you.