Yella Terra Problem...
11-22-2003, 09:23 PM
#21
Originally Posted by Beast96Z
It's a rocker arm. Why would it cause the graph to fall off? Looks to me like improper valvetrain geometry some how. I also lean more to the spring not being suited for the cam. If someone tells you that a spring is good for .615 lift, your just taking there word. ALWAYS get a open/closed seat pressure on the springs. Then find out from the seller of the cam what pressures are needed to keep the cam in check. I myself like a little more pressure than what is needed for comfort. It sounds like your MTI springs are at the max and giving out on the big end. If your going to run XE-R lobes, you need a stiffer spring to keep things right. I reccomend swapping to the new Crane duals.
The rockers were the only variable that was changed and the problem went away. The springs stayed the same.
If someone would just make one valid point as to why a rocker arm could or would hurt top end performance, I'd be very interested in hearing it.
11-22-2003, 09:33 PM
#23
It could be both the spring and the rockers actually. If there is more mass at the valve top from the YT rockers, that means more weight on the spring. That extra weight on the spring may be causing it to float in the high rpms. The stock rocker doesnt seem to have a much mass on the valve as a YT does, so maybe thats why when the stockers went on, less weight and no more float 
11-22-2003, 09:43 PM
#24
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Originally Posted by Country Boy
It could be both the spring and the rockers actually. If there is more mass at the valve top from the YT rockers, that means more weight on the spring. That extra weight on the spring may be causing it to float in the high rpms. The stock rocker doesnt seem to have a much mass on the valve as a YT does, so maybe thats why when the stockers went on, less weight and no more float
11-22-2003, 09:55 PM
#26
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Originally Posted by 2001CamaroGuy
is there? I thought the YTs had less mass.....
11-22-2003, 10:38 PM
#29
If someone would just make one valid point as to why a rocker arm could or would hurt top end performance, I'd be very interested in hearing it. There isn't much diffrence over the stocker other than stregnth.
11-22-2003, 11:02 PM
#30
The other car was running a TR230 cam with comp 987 springs...seeing as I don't know much about valvetrain dynamics, would the 987 springs be maxed with the lift on the TR230? As for my setup, the cam has .600 lift on both sides, so would the lack of flex contribute to pushing the springs past their limit of .615? I'm probably going to change cams again to one with less lift, but I'd like to figure this YT rocker situation out before I reuse them...
11-22-2003, 11:04 PM
#31
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I also weighed my YT's @ stock rockers before I installed them and they were lighter. I can't remember the actual numbers. I should have wrote them down but only did it our of curiosity.
11-23-2003, 08:44 AM
#33
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I thought I lost hp when I installed mine with my old setup. I ha d previously made 414 and after the rocker made only 402. I went and had it retuned and still just had about 405. took off the rockers and it was still low so it wasnt the rockers, i never did find the problem.
11-23-2003, 09:06 AM
#34
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Originally Posted by INMY01TA
http://www.fbodycentral.com/forum/sh...ghlight=Wilbur This guy did. Don't know if it's been resolved.
11-23-2003, 09:53 AM
#35
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When we checked PV clearnce with a jessel vs stock there was a huge diffrence in lift with the ratio being 1.7 of course. My point being even a yella terra rocker witch is in the same class as a jessel rocker when you pick up more lift it gona play hell on the springs and cause valve float.
11-23-2003, 10:11 AM
#36
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Originally Posted by Slowhawk
I would say valve float,but the YT's have to be set up right.I would do no more than .070 preload while ussing the YT's.
I got sick of hearing which is lighter and put both rockers on the scale at work.YT's are lighter!!
I got sick of hearing which is lighter and put both rockers on the scale at work.YT's are lighter!!
11-23-2003, 11:38 AM
#37
The post from F-body Central mentioned that an aftermarket lifter would be cause to set up the YTs differently or that the new lifter couldn't handle the pressure of double springs. My entire valvetrain consists of the following:
Comp XE-R 226/230 .600/.601 110
Crane lifters
MTI 7.4 chromoly pushrods
YT rockers
MTI double springs w/ titanium retainers
2.055/1.60 valves
MTI Stage II/LS6 heads milled .030
SLP double roller timing chain
Anyone see any compatibility issues? The lifters and pushrods were recommended by MTI, the double springs were part of the stage II head package from MTI...
Comp XE-R 226/230 .600/.601 110
Crane lifters
MTI 7.4 chromoly pushrods
YT rockers
MTI double springs w/ titanium retainers
2.055/1.60 valves
MTI Stage II/LS6 heads milled .030
SLP double roller timing chain
Anyone see any compatibility issues? The lifters and pushrods were recommended by MTI, the double springs were part of the stage II head package from MTI...
11-23-2003, 12:11 PM
#38
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Originally Posted by LawmanSS
The post from F-body Central mentioned that an aftermarket lifter would be cause to set up the YTs differently or that the new lifter couldn't handle the pressure of double springs. My entire valvetrain consists of the following:
If I were going to use double springs (especially a larger diamteter type spring like a 977) and YT's also, it seems pretty much necessary to upgrade to Comp R lifters or something similar.
Personally I have stock rockers/lifters with 987 springs and an XER cam and I'm starting to change my mind about getting a set of these YT rockers, atleast for the time being.
11-24-2003, 06:48 PM
#39
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Wow, this thread just answered a lot of questions for me.
I too have YT rockers, a TR 230 cam, and comp 987 double springs. I never had valve float until I added the YT rockers.
Bascially, my car is down 25rwhp/15rwtq @ 6800 rpms, and 50rwhp/30rwtq @7000rpms with the YT's vs. stock rockers.
The car seems to run fine but at 6600rpms my car's hp/tq output takes a nose dive.
Now, the 987 springs had a shade over 10,000 miles on them when I dynoed recently with the valve float. I just swapped in a new set but I'm sure I still have the same problems.
I may go re-dyno just to verify the dropoff with the fresh springs.
Dammit I should have gotten the Comp 921's.
I too have YT rockers, a TR 230 cam, and comp 987 double springs. I never had valve float until I added the YT rockers.
Bascially, my car is down 25rwhp/15rwtq @ 6800 rpms, and 50rwhp/30rwtq @7000rpms with the YT's vs. stock rockers.
The car seems to run fine but at 6600rpms my car's hp/tq output takes a nose dive.
Now, the 987 springs had a shade over 10,000 miles on them when I dynoed recently with the valve float. I just swapped in a new set but I'm sure I still have the same problems.
I may go re-dyno just to verify the dropoff with the fresh springs.
Dammit I should have gotten the Comp 921's.
11-24-2003, 08:21 PM
#40
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i have the exact problem myself... at about the same rpm the power takes a dive... i have Modified lifters ( like a Comp R style ) and 977s springs... 7.25 PRs / T&D Shaftmount rockers. I think the valves are hanging open... might want to look in that direction too...
only thing that might lend it to valve float in my instance is that the valves have different heights and i think the springs have different pressures.
only thing that might lend it to valve float in my instance is that the valves have different heights and i think the springs have different pressures.