roller rocker / de-tune question?
Thread Starter
Race Director
Joined: Jul 2001
Posts: 14,604
Likes: 3
From: Glendale, AZ
roller rocker / de-tune question?
ok guys, i have actually a de-tuning question.
i need some info on building an insanely hi HP motor but need a way to possibly tone it WAY down for emmissions.
should i build this motor around a 1.7 roller rocker and then go to 1.5 for de-tune? or would this not yield any results in my favor?
i want as much streetable HP out of this bad boy as i can, but i need a way to tone her down once every 2 years! any suggestions? i figured rockers would the an easy way to tame a wild cam and the swap should be relatively easy, more so than swapping the cam! :crazy:
i need some info on building an insanely hi HP motor but need a way to possibly tone it WAY down for emmissions.
should i build this motor around a 1.7 roller rocker and then go to 1.5 for de-tune? or would this not yield any results in my favor?
i want as much streetable HP out of this bad boy as i can, but i need a way to tone her down once every 2 years! any suggestions? i figured rockers would the an easy way to tame a wild cam and the swap should be relatively easy, more so than swapping the cam! :crazy:
Le Mans Master
Joined: Feb 2000
Posts: 9,715
Likes: 27
From: Kempner Texas
Re: roller rocker / de-tune question? (85_togo)
Using reverse math, you'd drop valve lift a little over .060 and reduce duration about 5 degrees, give or take, when you remove the 1.7s and install 1.5s.
Whether this would be enough to pass is anybody's guess. A lot will depend on your starting point; just how dramatic your mods before the rocker change.
I don't believe that just a rocker ratio change will do it though. It will probably call for several other mods involving ignition timing, fuel flow and exhaust.
Here's what I did:
Years ago I had a turbo Toyota Supra and I had installed an adjustable waste gate valve to allow higher boost, a second computer to richen the fuel mixture and which modified the timing. I also installed a free flow exhaust system. All bolt on stuff.
When emissions time came around I simply reinstalled the stock exhaust (only a few bolts involved), turned the boost gauge back to stock and readjusted the second computer fuel control back to stock also. Car passed with flying colors. Then, back in the garage, everything is reverted and I was good to go for another year.
I suspect you're going to have to do something very similar.
Hope this helps.
Jake
Whether this would be enough to pass is anybody's guess. A lot will depend on your starting point; just how dramatic your mods before the rocker change.
I don't believe that just a rocker ratio change will do it though. It will probably call for several other mods involving ignition timing, fuel flow and exhaust.
Here's what I did:
Years ago I had a turbo Toyota Supra and I had installed an adjustable waste gate valve to allow higher boost, a second computer to richen the fuel mixture and which modified the timing. I also installed a free flow exhaust system. All bolt on stuff.
When emissions time came around I simply reinstalled the stock exhaust (only a few bolts involved), turned the boost gauge back to stock and readjusted the second computer fuel control back to stock also. Car passed with flying colors. Then, back in the garage, everything is reverted and I was good to go for another year.
I suspect you're going to have to do something very similar.
Hope this helps.
Jake
Race Director
Joined: Oct 2000
Posts: 16,477
Likes: 1
From: Enter Post Count Here
Re: roller rocker / de-tune question? (85_togo)
It comes with the Holley Stealth Ram. :p:
With a programmable computer, you can run that thing on the smallest trickle of gasoline. It'll pass with open headers.
Bill Reid should be able to shed a lot more light on the subject than I can, he's been into the tuning more than me. I'm working on getting into it though.
I wouldn't mess with the roller rockers, get a set of 1.52:1's and be done with it.
With a programmable computer, you can run that thing on the smallest trickle of gasoline. It'll pass with open headers.
Bill Reid should be able to shed a lot more light on the subject than I can, he's been into the tuning more than me. I'm working on getting into it though.
I wouldn't mess with the roller rockers, get a set of 1.52:1's and be done with it.
Melting Slicks
Joined: Apr 2002
Posts: 3,019
Likes: 0
From: down that one road next to that big tree
Re: roller rocker / de-tune question? (olephart)
honda makes supras? lol..just had to poke some fun at the jokers :blueangel: supras are fun cars. pigs on the scale but still fun, they are also built better than our corvettes. take a 94 supra and 94 corvette down a bumpy road & see which one rattles more. GM did get it togeather on the C5 & a better build but that's another post :seeya
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Melting Slicks
Joined: Apr 2002
Posts: 3,019
Likes: 0
From: down that one road next to that big tree
Re: roller rocker / de-tune question? (gtsyellow)
also on topic. you never mentioned how much HP you were after. a basic approach to the insane street car is the zz4 or zz9 cam on a 200+ intake cfm flowing head @.500, 10:5-1 compression, a good piston like J&E, ross, wiseco etc. and a 150-200hp shot of no2. or you could go the blower route and just lower the compression to 9:1, at any rate 500 street legal HP are quite possible. were you after more?
Thread Starter
Race Director
Joined: Jul 2001
Posts: 14,604
Likes: 3
From: Glendale, AZ
Re: roller rocker / de-tune question? (gtsyellow)
also on topic. you never mentioned how much HP you were after. a basic approach to the insane street car is the zz4 or zz9 cam on a 200+ intake cfm flowing head @.500, 10:5-1 compression, a good piston like J&E, ross, wiseco etc. and a 150-200hp shot of no2. or you could go the blower route and just lower the compression to 9:1, at any rate 500 street legal HP are quite possible. were you after more?
