Rocker Ratio
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Rocker Ratio
Posted: August 03 2008 02:37 AM
 
Leo Gengler (aka roofcam34) [ View ] [ leogengler@msn.com ] [ Car Ads ] [ Blogs ]
Sioux City, Iowa
(712) 899-7440
 Leo (roofcam34)
 
Help out a dummy! For what reason(s) would I care if I went with a 1.5 or a 1.6 rocker arm ratio, when adding a COMP Thumper (283THR7 grind) hydraulic roller cam, new Beehive springs, retainers, and pushrods, in a ZZ4 350? The engine has the 1.5 ratio arms in it, and right now I'm planning on using those existing rocker arms. The engine has 3,000 miles on it. COMP recommends changing to their springs, retainers, and pushrods. Thanks for any help.
 
 
Comments
 
Posted by Crazyhorse Rod Shop  -  08/03/2008 08:23 AM
at over 500 lift i would really look for coil bind . i use the 268 extreme energy cam. i use all comp parts, springs/retainers/locks .stock rockers are fine for a street car.
dont poke the porchdog........he bites [ View ] [ Email ] [ Blogs ] [ Car Ads ] BLUFF DALE, Texas Charter Member since March 2003
 
Posted by housrace  -  08/03/2008 10:15 AM
Valve train geometry should be as close to 90 degree angles as possible to prevent coil bind, especially at speed. Wrong ratio rockers will create excessive angles and allow either the pushrod side or the valve side to not contact the rocker correctly. Either can cause catstrophic engine failure if it would occur at higher rpm's.
housrace [ View ] [ Email ] [ Blogs ] [ Car Ads ] Spfld., Illinois
 
Posted by Streetrodder007  -  08/03/2008 10:19 AM
You could use 1.6 ratio rockers if you want more valve lift. Moving from 1.5 to 1.6 rockers will give you a basic net lift of .010 more at the valve face. For a basic street motor there is nothing wrong with stock 1.3 or 1.5 rockers. I also like Comp Cams parts, but I always buy all the matching parts, you want good matching springs that can handle the extra valve lift without the binding.
Streetrodder007 [ View ] [ Email ] [ Blogs ] [ Car Ads ] Port Huron, Michigan Charter Member since April 2006
 
Posted by JAWS  -  08/03/2008 10:26 AM
From the factory Gm was shooting for a rocker ratio of 1.52. If you measure them all on your engine, you will find them vary from 1.3 ish to 1.5 ish. Just adding a set of actual 1.52 rockers will even the score when considering cylinder to cylinder performance. Seeing as your cam, cylinders, pistons, chambers, valves and the rest of the valve train are matched or real close to it, why would you want unmatched rockers.


Just a thought.


-Brant
An electrical headache can make a great car a pain [ View ] [ Email ] [ Blogs ] [ Car Ads ] Boise, Idaho Charter Member since August 2004
 
Posted by roofcam34  -  08/04/2008 12:48 AM
Thanks to all of you, for the always good help. This car is used for cruising and rarely sees real high RPMs. I'm just looking for a more nasty-idle (aggressive) characteristic than what I have now, without messing tooo much with the streetability issue. The parts I listed are what COMP suggests to get it. I didn't understand the "rocker ratio" thing, and saw the two options. As usual, you guys come through every time. My other concern is........(1) my crate engine has a pretty well mannered roller cam, with just a slightly noticeable "lope." (2) I'm not real sure of the results I'll get with the suggested cam, after spending another $600+.
Leo (roofcam34) [ View ] [ Email ] [ Blogs ] [ Car Ads ] Sioux City, Iowa
 
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