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-   -   Difference betw. 1.6 roller rocker and 1.7 roller rocker (http://www.moparchat.com/forums/showthread.php?t=37793)

BMELTON 10-08-2001 04:17 PM

Difference betw. 1.6 roller rocker and 1.7 roller rocker
 
This may be dumb, but I don't understand the difference between 1.6 and 1.7 roller rockers. I understand the roller part. That is the roller bearing on the tip that rolls and causes less friction right?? I can't comprehend how that can help hp much but, oh well. I want to add the R/T cam package and my searches have talked a little about both the 1.6 and 1.7 rollers. What does
the number mean?? I wanted to ask the parts guys at the dealer, but they are so arrogant, I cant stand to talk to them. You have to run the MP PCM with the R/T cam correct? I dont have emission testing here yet, but I am sure that within a year or two I will have to deal with that. I dont know if that makes a diff or not, but it sounds like it does according to another post that is going on now about the R/T cam.
Thanks
Bill

ScottnCincinnati 10-08-2001 04:39 PM

a 1.7 rocker will hold the valves open longer than a 1.6, kinda like putting in a "bigger" cam. the roller helps with power by eliminating friction(rolling instead of sliding). some 1.7 rockers will be too tall to fit with stock valve covers so pay attention to that too if you do rockers. with a stock cam 1.7's give about 5 hp more than 1.6's, don't know exact #'s but claims are 25hp increase over stock with 1.7 rollers

HighBlackRam 10-08-2001 05:28 PM

No need for a different PCM. The 1.7's do hold the valves open longer, but only because it opens them farther . They also have bearings at the pivot point, not just the tip. The number refers to the ratio of lift input to lift output. The stock ratio is approximately 1.5.

SUN RA KAT 10-08-2001 05:30 PM

You can run the R/T Cam Package without the Mopar PCM just like you can run the MoparPCM without the R/T Cam Package. They just work much better together, but late model 4X4s aren't going to get a Mopar PCM because Mopar isn't going to make it for the 4X4s but they can get a pretty healthy increase of torque & horsepower and stay in the EPA emission standard with just the R/T Cam Package & heavy duty valve springs.

The Mopar 1.7 roller rockers (and the 1.6 roller rockers) are not for sale or use on pollution controlled vehicles er the Mopar Performance Parts catalog which means unless you swear or sign a statement that you are not going to drive your vehicle on public roads your friendly Mopar parts man isn't allowed to sell them to you. He probably will though, but the service manager may not install them. But he might. These roller rockers will need periodic adjustment which is why they are not for sale or use... Also, in the case of the 1.7 roller rockers, they are not EPA certified. They also need modicfication to the stock valve covers, or better yet, the Mopar Magnum valve covers. I think cmyindy has both the R/T Cam Package and the 1.7 roller rockers and he passes emission testing though.

I was told the 1.6 rr would give me about 5-8 more horsepower so I didn't think they were worth the expense and hassle of periodic adjustments. (Open your hood & see how much room you have to remove your valve covers & adjust the valves and put the covers back on again.) The 1.7 rr were not available when I put on the R/T Cam Package, but I have been told that they will give an increase of 10-15 more horsepower, which may make them worth it.

DodgeMan79 10-09-2001 02:44 AM

Since the 1.7 rr and 1.6 rr make things stay open longer. Will selecting the 1.7 or the 1.6 depend on the mods or does the .1 difference, make a difference?

eddieeddieg 10-09-2001 08:45 AM

SUN RA KAT:
In the 2000 Mopar Performance Catalog
Part #4876050 is a replacement rocker arm set
for the 92-99 Magnum and crate engines.
stating "Production 1.6 design ratio"
Is this a typo? Should it be 1.5 ratio?

Thanks
Eddie

SUN RA KAT 10-09-2001 10:48 AM

eddieeddieg - stock Magnum engines come with 1.6 ratio rockers. Going to a 1.6 roller rocker only gives you more performance because the friction is less than the stock 1.6 rocker. The 1.7 roller rocker gives you the same less friction advantage as the 1.6 roller rocker does and also opens the valves a little more (duration = top end horsepower & lift = low end horsepower). The 1.7 roller rockers on the stock cam brings the total specs closer to the R/T Cam. The 1.7 roller rockers on the R/T Cam bring the specs up to aftermarket more agressive grinds and still keeps eerything Mopar.

IWantMoreRamStuff 10-09-2001 12:36 PM

worth pointing out
 
... too that many performance parts like these are perfectly capable of passing emissions tests, but that testing/certification process is expensive. So often times a company won't bother.

If they do decide to submit to the testing process, they have to know that they're going to be able to spend enough on marketing and sell enough units to re-coup their expenses.

On the other hand, you never know for sure with the non-certified parts whether or not they're going to cause you to fail emissions testing. In this case (1.7 rockers and a MP cam), there are people who have passed emissions without problems, so that shouldn't be an issue.

cmyindy 10-09-2001 01:37 PM

go for it.
 
BMELTON i have the r/t cam and 1.7 rr and pass the smog test with no problems. i even have ported heads. thanks cmyindy

HighBlackRam 10-09-2001 01:41 PM

Sun,
I thought the stock rockers were not a true 1.6 ratio, and there was some performance to be gained by switching? If they were the same, could you even measure the HP difference due to reduced friction?

SUN RA KAT 10-09-2001 03:19 PM

HighBlackRam - the stock rockers are a true 1.6 ratio. The performance gain of 5-8 horsepower is due to less friction. I was told once that you can feel (seat-of-your-pants) a 10 horsepower inrcease, but not a 5 hosepower increase, which is why I didn't get the 1.6 roller rockers when I had my R/T Cam put on. The 1.7 roller rockers weren't available as a Mopar Performance Part at that time.

HighBlackRam 10-09-2001 03:27 PM

Something else to put on the list then. I usually stay away from things like that because of the smog situation here, but if they can't see it and it burns clean.........

SUN RA KAT 10-09-2001 03:34 PM

I'd go with the 1.7 roller rockers, but I would think seriously on whether you're addicted like me to doing mods. If you are, do it right the first time and get the R/T Heads and the 1.7 roller rockers at the same time to save money on installation labor. And don't forget Mopar Magnum Valve Covers so the 1.7 rr will fit.


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