5.9 question. Cam or roller Rockers - JeepForum.com
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post #1 of 21 Old 01-05-2017, 11:36 AM Thread Starter
Runts
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So I own a 98 5.9 zj and I'm looking to get more power out of it. Right now I've got, m1 intake 2bbl, 52mm throttle body, Doug Thorley headers, and a full exhaust. Also is tuned for the upgrades

So my question is should I go with 1.7 roller Rockers? Or a cam? Or could I do both?

Also what else would need to be done to accommodate the roller Rockers/cam?

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post #2 of 21 Old 01-05-2017, 11:50 AM
jeepjeepster
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Whats the tune you speak of?

While I imagine some gains are there, once you get a cam the heads will be restricting. So if you do a cam you should go ahead and do the heads.

If you get a cam with the lift you want, theres no reason to get 1.7 rockers.

Get with ryan and get a custom tune if you go for the cam/heads.

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post #3 of 21 Old 01-05-2017, 12:21 PM Thread Starter
Runts
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Originally Posted by jeepjeepster View Post
Whats the tune you speak of?

While I imagine some gains are there, once you get a cam the heads will be restricting. So the if you do a cam you should go ahead and do the heads.

If you get a cam with the lift you want, theres no reason to get 1.7 rockers.

Get with ryan and get a custom tune if you go for the cam/heads.
The tune I have on it right now in from Ryan. He's actually sending me an updated one today. But that's what I figured. No reason to do both. So if I'm going to go with a cam, what cams should I be looking at? I don't know much about the specs on them. Any place I can read up on this stuff? Like what heads I should go with with a certain cam etc.
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post #4 of 21 Old 01-05-2017, 01:25 PM
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Originally Posted by jeepjeepster View Post
If you get a cam with the lift you want, theres no reason to get 1.7 rockers.
It really depends on the cam; some provide you with more valve lift with the OEM 1.6 ratio rockers. Some don't.


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Originally Posted by Runts View Post
So my question is should I go with 1.7 roller Rockers? Or a cam? Or could I do both?

Also what else would need to be done to accommodate the roller Rockers/cam?
If I were you, I'd do both a more aggressive cam and 1.7 ratio roller rockers - depending on the cam, and if you have enough room for the 1.7 ratio roller rockers. Roller rockers IMO won't gain you much power (if any) with an OEM or mild cam, but they do make the life easier for the valvetrain with a more aggressive cam profile.

If you go with a new cam, you need at least new lifters (all Magnums use hydraulic roller lifters) and preferrably new chrome-moly pushrods. Like I mentioed above, I do suggest roller rockers as well. Some people will disagree with that statement


OEM heads don't flow too well. Porting them & machining for bigger valves is.. well.. some say go with it, but I'd call it polishing a turd Either go with Indy heads, or do like me and buy a set of Edelbrock Performer RPMs. You can't go wrong with them, and they will leave you with quite a bit of possibilities for future upgrades on the power if you want to.
If I remember correctly, according to Ryan even the OEM Siemens Deka 1-hole injectors should be good for up to around 350-400 horses.


My current setup is Edelbrock Performer RPM aluminum heads (61775), Comp cams 20-744-9 cam (I probably should've gone with something a bit more aggressive), Comp cams 1602-16 Ultra-pro magnum 1.6 ratio roller rockers (Edelbrock uses stud-mount GM SBC-type rocker) + matching length Edelbrock chromo- pushrods.
OEM thottle body + DIY ported kegger.
I will buy a Hughes FI Airgap intake + larger throttle body, or if I come across an M1 4bbl at a reasonable price I sure will buy that. When I have the intake + TB installed, I will get a Flyin' Ryan tune. I certainly could use one now - stock 5.9 PCM does work, but there's definitely more ponies and torque under the hood that are held back because of the stock tune on the PCM.


Keep in mind things escalate pretty damn quickly I started with doing the plenum plate fix with a Hughes Engine plenum plate upgrade - and ended up pulling the engine and investing almost 4k on it Too bad - or thank God - I ran out of money. If had had more to spend, I would've stroked it to 408

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 #5 of 21 Old 01-05-2017, 03:46 PM
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Quote:
Originally Posted by Timo_90xj View Post
It really depends on the cam; some provide you with more valve lift with the OEM 1.6 ratio rockers. Some don't.
Are you saying that with some cams you can lose lift with 1.7 rockers versus 1.6 rockers? Rockers are just simple levers. With a 1.6 ratio however much the cam pushes up the lifter and push rod gets multiplied by 1.6 at the valve. With 1.7 rockers they machine the push rod cup closer to the fulcrum to give you 1.7 times the cam motion at the the valve. Not really any way to go from 1.6 to 1.7 and lose valve lift or vice versa.

There are a couple things to watch out for in general with higher ratio rockers. You lose push rod clearance since the push rod moves toward the valve. Higher ratio rockers also put more stress on the rocker and rocker bolt so they aren't good for aggressive cams. Most mild street cams it won't make a difference. If you're buying a new cam just buy the cam you want and use stock ratio rockers. If you want more lift buy a bigger cam.
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post #6 of 21 Old 01-05-2017, 04:21 PM
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Originally Posted by zjosh93 View Post
Are you saying that with some cams you can lose lift with 1.7 rockers versus 1.6 rockers?
Nope, I'm saying that with the same cam you get more valve lift from the 1.7 ratio rockers compared to a 1.6 ratio.

..or, some cams provide more or less lift with the same rocker ratio. As you certainly know, there are different cam profiles. Of course, there isn't much room to play with on pushrod engines due to the cam bearing bore clearance.


Quote:
There are a couple things to watch out for in general with higher ratio rockers. You lose push rod clearance since the push rod moves toward the valve. Higher ratio rockers also put more stress on the rocker and rocker bolt so they aren't good for aggressive cams. Most mild street cams it won't make a difference.
This exactly, and that's what I wrote above as well. That is also the reason why one wants roller rockers & hardened and/ or chromo pushrods with a more aggressive cam profile. It is also the reason why hydraulic roller lifter cams can be machined much more aggresively compared to a flat tappet came if you want it to survive more than 1000 miles on a race track


Quote:
If you're buying a new cam just buy the cam you want and use stock ratio rockers. If you want more lift buy a bigger cam.
Bigger cam only provides more lift if the cam bearing clearance allows for it. Ie. my cam would provide .512" lift with 1.7 rockers, but with the current 1.6 rockers it's only .482" - and there's not really much room to play with on ie. our Magnum engines. It's not really much different from the stock cam with the 1.6 ratio even though the cam profile and valve opening/ closing and other parameters are different.
Bigger cams mostly play with the valve open/ closing degrees, etc... they can and do also have different grinding for quicker valve opening and closing.
Rocker clearance can be an issue when using roller rockers with stock valve covers (even with OEM cam), so aftermarket valve covers are a good idea.

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***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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post #7 of 21 Old 01-05-2017, 04:34 PM
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Originally Posted by Timo_90xj View Post
Nope, I'm saying that with the same cam you get more valve lift from the 1.7 ratio rockers compared to a 1.6 ratio.
I figured you had the right of it but on my first read I had that record scratch moment.

Interesting fact for those not familiar: most cams for a given engine are ground off relatively few cam blanks. The only way to get a bunch more lift is to grind the base circle smaller or as Timo mentioned it won't fit in the cam bearings; which is why you always have to check push rod length on aftermarket cams. This weakens the cam somewhat. Really big cams look positively spindly.
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post #8 of 21 Old 01-06-2017, 07:16 AM
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Its hard to say 'get this cam.' For awhile I was dead set on putting new heads and a cam in my 5.9 but I backed down. I even bought new EQ heads and had them mildly ported... Theyre sitting under my bed currently. Check out the speak freaks forum and just start searching threads. Theres a lot of info out there if you can find it. I wouldve most likely went with the 210/220 .512/.512 110lsa. Its a pretty common cam. Just make sure the valve springs can handle whatever you plan on going with. I told clear water cylinder heads that I was going to get a cam with 0.512 lift and they sized the springs accordingly. I got scared since I dont trust them and bought a set of mopar 0.600 springs.. Which are sitting in a box in my garage.. Also bought mopar valve keepers and retainers. Along with mopar valve seals... I think the thing that scared me the most was making sure the push rod length was correct. Something Ive never done and I didnt want to screw up my low mile niner, so I backed down. Settled for a mopar m1, 1.7 HS rockers, 52mm TB, DT headers, full 3" kolak exhaust, and ryans tune. Ryan can give you all sorts of info on what cam is the best.

Also check out the dakota RT forum. Lots of info there also

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post #9 of 21 Old 01-06-2017, 08:04 AM
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Quote:
Originally Posted by jeepjeepster View Post
I think the thing that scared me the most was making sure the push rod length was correct. Something Ive never done and I didnt want to screw up my low mile niner, so I backed down.
I doubt you would screw it up if you checked the pattern where the roller rides on the valve stems. I think the worst you see would be clattering and she may run badly. The roller needs to be 'centered' atop the valve stem. There is plenty of info out there about that.

You can use 'valve stem lash caps' to add surface and length to the end of the valve stem. And these caps have the same effect of lengthening the pushrods, and you would likely need longer pushrods with a hotter cam. The caps make the centering more forgiving too. You can shim the pedestals to realize a virtual shortening of the pushrod length. Just a couple examples of what I am talking about, not necessarily what you need..
https://www.summitracing.com/search/...alve-lash-caps

https://www.summitracing.com/parts/c...Qb0aAmMX8P8HAQ

The lifters give you about .03" of slop to play with. And roller rockers themselves allow a good bit of adjustment in either direction, so pushrod length is not as critical as it is with the stock valvetrain. The stock pushrods are 6.935". I found through trial and tribulation that the stock length is the magic number in most situations.

So you need to make sure of two things...the roller is sitting atop the valve stem properly and the lifter preload is near the center of the range. The center of range is where the noise is least. As you get away from the center of range you will hear clattering.
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post #10 of 21 Old 01-06-2017, 10:00 AM
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Since you have pedestal mount rockers the rocker geometry should be good so you should just need to find the right length rod. With the right push rod you won't need shims unless there's a lot of variability in your head machining or cam machining or you really want to dial in the rocker arm geometry. Assuming the stock rockers have good geometry then all you need to do it put the cam on the base circle and adjust the push rod length out to take up all the lash.

Checking push rod length is pretty straight forward. You generally want about 30 thousandths preload on the plunger (0.030"). The actual plunger travel is greater than that usually around 0.14" but you run into problems with the plungers pumping up if you stray from the recommended preload. First thing to do is buy a spare lifter, gut it, and shim it internally to make it solid with the cup 0.030" down from fully up. Get a stock push rod and cut it in half, tap both sides 1/4-20, and screw your new adjustable push rod together with a piece of threaded rod. Make sure the cam is on the base circle for the lobe you are checking. Drop the solid checking lifter (might want to mark it so you keep it out of your finished motor) into the motor followed by the adjustable push rod set to stock length.

To check rocker geometry, mark the top of the valve with dykem or sharpie marker. Turn the engine over and watch the rocker tip. It should start just inside of the center of the valve stem then push to just outside the center and back as it opens then reverse as it closes.
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post #11 of 21 Old 01-07-2017, 06:25 PM
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Ryan and his datalogs will be able to tell you what will make a better bang for your buck way better than we can.


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post #12 of 21 Old 01-07-2017, 11:55 PM
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Not a whole lot of point to just doing 1.7 rockers on a stock 5.9 if you really want to make power. That'd only take you from .410 valve lift to .436, which is basically into stock 5.2 cam (.432) territory - not exactly pushing the limits of performance. I'd be looking for at least .500 and you can't do that with just rocker arms - so you may as well get the right cam to begin with and stick with the 1.6s with a new set of springs.

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post #13 of 21 Old 01-11-2017, 06:05 AM Thread Starter
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so you may as well get the right cam to begin with and stick with the 1.6s with a new set of springs.
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?
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post #14 of 21 Old 01-11-2017, 07:15 AM
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You don't have to, but OEM heads are going to be the restricting part at some point sooner or later. Depends on your intake setup, exhaust setup, desired valve sizes, etc..

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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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post #15 of 21 Old 01-11-2017, 08:52 AM
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You really want to approach this as a whole. Pick a power number you want to hit then pick parts that will work well at that power level and your budget. It all works together: the cam requires a certain compression ratio, the heads and intake need the right flow at the right lifts, the exhaust needs to be sized to reduce restriction at that power level. Just putting a bigger cam in it will, within reason, give you more power, but you're leaving power on the dyno floor if you are choking it with mismatched parts.

I'd call one of the cam companies and talk to them. The cam they recommend is going to be your best choice almost every time.
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