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9RT9
Dodge Dakota
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12/19/2004
23:55:15
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 Subject: 1.6 or 1.7 RR
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I just bought a new cam for my 99 R/T. The cam is mopar performance P5007551, 272/278, 467/482. What would be the best ratio to go with it 1.6 or 1.7 roller rockers? Thanks for any help.
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ScojoDak
Dodge Dakota
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12/20/2004
00:31:31
| RE: 1.6 or 1.7 RR
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Word has it if you're doing a cam mod to stay with the 1:6's. 1:7's if you're staying with a stock cam.
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rtdkota
R/T
12/20/2004
15:12:39
| RE: 1.6 or 1.7 RR
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You can get more out of that cam (it's small) with 1.7s--- you'll need to run valve springs for either ratio.
I sell both 1.6 and 1.7 ratio (Crower)...
I can hook you up!
Sam
www.socaldakota.com
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.boB
Dodge Dakota
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12/21/2004
23:38:40
| RE: 1.6 or 1.7 RR
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All the bigger ratio does is increase valve lift. It does not change the cam profile, duration, overlap, or lobe center. That's not a bad thing, and sometimes that's just what your engine needs. But you have to be carefull about mixing and matching parts. Get too much lift, and the valve and the piston try to occupy the same space at the same time. Structural Physicists and engineers have a term for that - "bad". ;)
Anyway, The cam you now have has a total valve lift of .467/.482. The cam card usually provides gross valve lift - usually at 1.6 - and lobe lift. If we assume that your specs are listed for a 1.6 rocker (stock), that gives you a gross lobe lift of .292/.301. Calculate for a 1.7 rocker and you get .496/.512 valve lift.
Now, whenever you get lifts greater than .500, you need to be very careful about clearance issues. Unles you are absolutly sure this combo will work, don't do it without claying the pistons.
Also, run it through Desk Top Dyno and see what kind of power gains you'll get for all that extra work and money. You may decide it's not worth it. BTW, DeskTop Dyno isn't absolutly accurate, but it's very usefull for parts comparisons prior to turning a wrench or spending a dollar.
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rtdkota
R/T
12/22/2004
15:38:15
| RE: 1.6 or 1.7 RR
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Actually the limit on stock config is in the .540 lift range-- that's where you get into issue. You do need to run springs for anything over the stock cam-- or if you plan on running higher than 5500 rpm on the stock cam.
I run a .512/512 cam (based on 1.7 ratio)--- no problems... and have sold quite a few as well to many happy customers.
Sam
www.socaldakota.com
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99DAK
Dodge Dakota
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12/22/2004
17:26:30
| RE: 1.6 or 1.7 RR
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I have the Mopar R/T cam 1.7 rr's and used the Mopar recomended springs. wheeeeeeeeeeeeeeeee Ha
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