questions for 1.8 roller rocker owners
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questions for 1.8 roller rocker owners
Has anyone had 'problems' or unexplicable loss of hp up top, when using 1.8 RR's, or more specifically, the yella terra 1.8's? My dyno curve noses over pretty good up top, and I was told that it may be due to the YT 1.8's.
Thanks!
Thanks!
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Originally Posted by Greg Fell
Has anyone had 'problems' or unexplicable loss of hp up top, when using 1.8 RR's, or more specifically, the yella terra 1.8's? My dyno curve noses over pretty good up top, and I was told that it may be due to the YT 1.8's.
Thanks!
Thanks!
I had the same big dip in power starting at ~5900 rpm when I first installed my 1.80 roller rockers. They just didn't like my PRC dual springs and when I swapped in a set of Crane duals, the dip disappeared and I picked up 10 extra rwhp over the SLP 1.85's I previously had installed.
#3
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I dynoed today and have the dip at about 5,900 RPM. Makes great power then rolls over. Wondering if the advance in the cam is acentuated somehow by the bigger rocker ratio. Car pulls hard, but then dips. At 6,300 it starts coming up again so it might be KR but tuner says no. It is about a 25 HP dip before it recovers. I don't think it is valve float as it would recover at higher RPM.
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Mine was valve float caused by valvetrain harmonics @ 5900 rpm and it did recover (though not fully) at around 6200-6300 rpm. I'd suggest a valve spring swap and hope for the best.
Are you using the Crane duals now? If so, maybe a set of the Comp beehives would do the trick for you? I'm pretty darn sure it's valve float that your motor is experiencing and not something else. If it's KR, that's easy enough to check for.
Good luck!
Are you using the Crane duals now? If so, maybe a set of the Comp beehives would do the trick for you? I'm pretty darn sure it's valve float that your motor is experiencing and not something else. If it's KR, that's easy enough to check for.
Good luck!
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Originally Posted by XTrooper
Mine was valve float caused by valvetrain harmonics @ 5900 rpm and it did recover (though not fully) at around 6200-6300 rpm. I'd suggest a valve spring swap and hope for the best.
Are you using the Crane duals now? If so, maybe a set of the Comp beehives would do the trick for you? I'm pretty darn sure it's valve float that your motor is experiencing and not something else. If it's KR, that's easy enough to check for.
Good luck!
Are you using the Crane duals now? If so, maybe a set of the Comp beehives would do the trick for you? I'm pretty darn sure it's valve float that your motor is experiencing and not something else. If it's KR, that's easy enough to check for.
Good luck!
What sucks is I love this setup and the car is very very strong Just have to figure out the quirk and correct it.
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#9
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Greg,
Did you see this post? Turns out it was his cats, but the tuner thought it was the rockers. Curve looks similar to yours, but at a lower RPM.
Dyno Thread
Did you see this post? Turns out it was his cats, but the tuner thought it was the rockers. Curve looks similar to yours, but at a lower RPM.
Dyno Thread
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I have the comp pro magnums( 1.85 ) and I was experiencing the same loss of power up top like you guys. I thought a quick fix would be to swap in some 05 LS6 springs that were available. Well it seemed to fix it, but then I realized it only moved the problem a little more up the curve. It was major valve float with my stock springs!( .541 lift on stock 98' springs= ) Now not so bad, but I'm still not that happy! I don't know whether to get some 1.7's or new springs. I don't want to give them up yet! It still does'nt shift at WOT without letting off this is valve float right?
TIA
Jon
TIA
Jon
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Originally Posted by vettenuts
Greg,
Did you see this post? Turns out it was his cats, but the tuner thought it was the rockers. Curve looks similar to yours, but at a lower RPM.
Dyno Thread
Did you see this post? Turns out it was his cats, but the tuner thought it was the rockers. Curve looks similar to yours, but at a lower RPM.
Dyno Thread
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Originally Posted by quickneSS
I have the comp pro magnums( 1.85 ) and I was experiencing the same loss of power up top like you guys. I thought a quick fix would be to swap in some 05 LS6 springs that were available. Well it seemed to fix it, but then I realized it only moved the problem a little more up the curve. It was major valve float with my stock springs!( .541 lift on stock 98' springs= ) Now not so bad, but I'm still not that happy! I don't know whether to get some 1.7's or new springs. I don't want to give them up yet! It still does'nt shift at WOT without letting off this is valve float right?
TIA
Jon
TIA
Jon
I have Patriot Golds, which are about the stiffest spring you can use with a hydraulic lifter.
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Greg,
What happened with the stock rockers? I am looking at shimming mine to get the issue above where I want to set my rev limiter. Looking for shims now and a new way to turn over the motor. I had a special tool made for when I had the stock balancer and bolt, but now with the ATI balancer and ARP bolt it doesn't work and I have to figure this out as well
What happened with the stock rockers? I am looking at shimming mine to get the issue above where I want to set my rev limiter. Looking for shims now and a new way to turn over the motor. I had a special tool made for when I had the stock balancer and bolt, but now with the ATI balancer and ARP bolt it doesn't work and I have to figure this out as well
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Attached is the results. Good news/bad news.
I did 484/459 at speed inc in may.
I have sinced added FAST 90, 1.7 stock rockers, stock TI zo6 exhaust, and dyno'ed 484/459!?!?! But the curve is most def better. I guess losing the lift and changing the exhaust negated the FAST 90.
I ran the car last night, and ran 10.85 @ 129.6 with a 1.55 60' bumping the rev limitter in 3rd. May have been a 130 mph trap speed
I did 484/459 at speed inc in may.
I have sinced added FAST 90, 1.7 stock rockers, stock TI zo6 exhaust, and dyno'ed 484/459!?!?! But the curve is most def better. I guess losing the lift and changing the exhaust negated the FAST 90.
I ran the car last night, and ran 10.85 @ 129.6 with a 1.55 60' bumping the rev limitter in 3rd. May have been a 130 mph trap speed
Last edited by Greg Fell; 10-09-2005 at 11:20 AM.
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I am running the patriot golds. I do not know if they are shimmed, I believe they are installed at 1.800. Not sure.
I think I lost some power from less lift, but I have already bent valves from the valve float, and I think they extra revs will benefit me as I can stay in a deeper gear and get some mechanical advantage there. My traps went from 126ish to 129.6 last night, granted the weather was nice.
I'm switching to the LS7 stuff anyway, so I'll just be happy with the stockers for now.
I think I lost some power from less lift, but I have already bent valves from the valve float, and I think they extra revs will benefit me as I can stay in a deeper gear and get some mechanical advantage there. My traps went from 126ish to 129.6 last night, granted the weather was nice.
I'm switching to the LS7 stuff anyway, so I'll just be happy with the stockers for now.