5.9 question. Cam or roller Rockers - Page 2 - JeepForum.com

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post #16 of 21 Old 01-11-2017, 03:15 PM
CatSplat
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Originally Posted by Runts View Post
Any recommendations? I'm also being told that I'm gonna need to upgrade my heads entirely. Or is that incorrect? Where can I get a nice set of springs that'll work with the stock heads?
That really depends on what kind of power you want to make. More power means you need more supporting mods. The stock heads aren't terrible, but they're not flow monsters either. Your cam selection can be influenced by compression ratio and other factors as well.

With that said, you can still make good power with a bigger cam on a stock-ish motor, it just won't be using the cam to its greatest potential. Max lift on stock heads is ~0.520 before you run into retainer/valve guide clearance problems. Some guys have run as high as ~.540 but casting variation may account for that. If you only wanted to go with a bigger cam, I'd look at a nice custom grind like this one, and anybody that sells a custom grind Magnum cam should have some suggestions on what springs to use with it.

You have good supporting mods already (intake, exhaust) so while your heads will likely be the bottleneck, with a good tune you should get a very noticeable power boost. Your engine specs are (cam aside) very close to the Mopar 5.9 380HP crate engine, although it may have had a bit higher compression. The cam in that unit was a .501/.512 lift IIRC.


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post #17 of 21 Old 01-12-2017, 11:14 PM
Bodybuilder21
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You don't have a lifetime SCT by chance do you? If your deciding between a cam and roller rocker's for more power; i'd say neither. Save up for Eldelbrock RPM head's..then make a decision if you'd rather have a meaner, throaty idle with more low end/ raw power with an aggressive lopey cam..or if you'd like to to add roller rocker's and get a little quicker throttle response, the unmatched sound of roller rocker's rapidly pumping away,along with that distinct, crisp exhaust tone. Take into consideration that Magnum head's are known to crack, especially with high mileage and put under more stress so EVENTUALLY they'll need to be replaced sooo just something to consider

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post #18 of 21 Old 01-13-2017, 11:27 AM
Timo_90xj
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I certainly second the Edelbrock RPMs (part # 61775).. they are great!

Then again, when you have the engine partially open already, it's a good time for cam & roller rocker upgrade at the same time Expect things to get (seriously) out of control once you start unbolting parts and get a bit carried away browsing Summitracing for new parts

1998 Grand Cherokee 5.9 LX daily driver, 1.75" BB, 32" KM2s, HPD30 Eaton e-locker/D44a stock LSD, 4.56 gears, custom- fabbed tube bumpers and tube fenders,...


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post #19 of 21 Old 01-13-2017, 12:58 PM
CatSplat
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Yeah, it's really easy do go down the power-adder rabbit hole. If you want to make some extra power and keep costs down, just go with a good cam that works with your current setup.

1994 5.9L ZJ, retrofitted UC package, NP242 swap, 17" JK Moabs with 32" BFG MT KM's.
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post #20 of 21 Old 01-13-2017, 03:41 PM
zjosh93
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The Edelbrock heads basically require roller rockers though. It says "accepts small-block Chevy adjustable 1.6 ratio rockers..." I'm not sure what the geometry differences are between stock Magnum rockers and small-block Chevy parts but I doubt your stock rockers are going to work. Might as well throw a cam in there as well, while you're in there.
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post #21 of 21 Old 01-13-2017, 03:57 PM
Timo_90xj
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Yeap, Edelbrock RPM 5.2/5.9 Magnum heads use SBC- style stud-mount rockers, instead of the Mopar pedestal mount. OEM rockers or pedestal-mount roller rockers won't work. You need the Chevy style. ....which is not necessarily a bad thing






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1990 XJ Limited (4-door), 4.0 I6, AW4, NP242, ***rolled and totalled @ 165k miles***

***Under construction***
1990 XJ (4-door), 4.0 I6, AW4, NP242, PBR 42" tires, Unimog 404 portal axles, 110" WB, full cage + uniframe completely rebuilt, front 3-link + panhard / double triangulated 4-link rear,... ***SOLD***
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