Yella Terra Problem...
TECH Junkie
Joined: Jan 2002
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From: At the office
my YT's are coming off this weekend until I get new springs. I run the same springs Nic is talking about, with a bigger cam and more lift/duration, plus I spend more time above 6200rpms than he does. I wonder how this will affect track performance. 
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TECH Junkie
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Joined: May 2003
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From: Pittsburgh, PA
Originally Posted by jmX
The YT's are 1.71:1, GM's are 1.68:1
I don't agree with the dynamic in this thread, the Y/T's are better than stock, and there is nothing wrong with them. Stock rocker arms would you think about it (feel free to correct my terminology) have more deflection since they are stamped. Now that being the case, what could increase valve float hmmm by having less deflection? Maybe someone can look into the geometry of the setups.
I will say that most combos really don't pull up to 7000 rpms on the dyno most springs will not work after 6600 rpms.
I will say that most combos really don't pull up to 7000 rpms on the dyno most springs will not work after 6600 rpms.
I believe the YT's actually give more lift causing the springs to float. We pick up HP in the higher rpms but at the expense of a few ponies under 3500rpm. You definitely need to use the right spring with these or you will get float with these rockers. I tried them with a set of 987 CC springs and it floated at 6400rpm. Switched to 985 which has better pressures and the float moved up to 6800rpm. Still need a little more spring. Even with the float in the 6800rpm the car still makes 10 sec runs on motor. Time to try out some Cranes.
Good points Mark, I was thinking that something along those lines is happening.
What is the open and close pressure of 987's?
I am running a big crane single they are setup up at like 145 on the seat.
What is the open and close pressure of 987's?
I am running a big crane single they are setup up at like 145 on the seat.
