WHY SPLIT ROLLER ROCKER RATIOS?
Thread Starter
Drifting
Joined: Jun 2002
Posts: 1,305
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From: Savannah Ga.
WHY SPLIT ROLLER ROCKER RATIOS?
Does spliting the ratio on roller rockers add up for more HP/tor.....often times i see 1.6 matched with 1.5.......one side for intake another fo exhaust..another question which side in a LT1 is intake and exhaust :conehead
p.s. also saw someone running 1.7 with 1.6.......holler back!!!
[Modified by redcorvettedave, 12:20 AM 2/14/2004]
p.s. also saw someone running 1.7 with 1.6.......holler back!!!
[Modified by redcorvettedave, 12:20 AM 2/14/2004]
Team Owner
Joined: Jan 2004
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From: NJ
Re: WHY SPLIT ROLLER ROCKER RATIOS? (redcorvettedave)
It doesnt necassarily mean more HP. During testing of you car or engine you may find a situation that dictates the need for more intake/exhaust flow to tune the HP or torque curve. This is just one way to get it. I cant really give any rock solid situations where this would be the norm because I never used this particular mod but I would say its all in the engine or combonation design.
[Modified by Chevy Guy, 12:26 AM 2/14/2004]
[Modified by Chevy Guy, 12:26 AM 2/14/2004]
Race Director
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From: The Top of Utah
Re: WHY SPLIT ROLLER ROCKER RATIOS? (redcorvettedave)
Particularly in the Gen I engines, the exhaust ports don't flow up to par with the intakes. When split, the exhausts usually get the higher ratio.
On the LT1s, the intakes are on the left. :lol: :lol: :lol:
RACE ON!!!
...another question which side in a LT1 is intake and exhaust :conehead
RACE ON!!!
Team Owner
Joined: Dec 2000
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From: SE NY
Cruise-In II Veteran
Re: WHY SPLIT ROLLER ROCKER RATIOS? (redcorvettedave)
It was found that installing 1.6s on the exhaust of an '85 Vette (iron heads) brought no hp gain over just 1.6s on the intake but did cause idle roughness.
I was going to split them on my '88 L98 but decided to just install 1.6s around and the idle was smother than with stock 1.5s on all valves.
I don't think you will have a problem installing 1.6s around on a LT1 engine nor would splitting the ratios gain you any more chp.
However I would split ratios if necessary to keep valve lift in the region so that I could use single springs on all valves.
[Modified by 65Z01, 9:49 PM 2/13/2004]
I was going to split them on my '88 L98 but decided to just install 1.6s around and the idle was smother than with stock 1.5s on all valves.
I don't think you will have a problem installing 1.6s around on a LT1 engine nor would splitting the ratios gain you any more chp.
However I would split ratios if necessary to keep valve lift in the region so that I could use single springs on all valves.
[Modified by 65Z01, 9:49 PM 2/13/2004]
Thread Starter
Drifting
Joined: Jun 2002
Posts: 1,305
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From: Savannah Ga.
Re: WHY SPLIT ROLLER ROCKER RATIOS? (65Z01)
------------------------------------------------------------------------
On the LT1s, the intakes are on the left. :lol: :lol: :lol:
________________________________________ ___________
:conehead is the driverside the left!!! :hat :conehead :jester
Drifting
Joined: Dec 2002
Posts: 1,861
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From: Houston TX
Re: WHY SPLIT ROLLER ROCKER RATIOS? (redcorvettedave)
Long and short of it is that you usually see split ratios when the engine tuner finds that they didn't spec the right cam for the motor when the motor was being built. It's not uncommon to see in high end racing engines because the cams cost so much money (custom ground billet cams) that it's a lot cheaper to swap ratios than it is to replace the cam. However, you'll also see the split rockers go away and the right cam go in once they're past the R&D stage of the combo.
Drifting
Joined: May 2003
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From: Lakeport CA
Re: WHY SPLIT ROLLER ROCKER RATIOS? (CorvetteZ51Racer)
:iagree: with all the above. TPIS dyno testing showed no real increase on the intake side for the L98. My idle was a little lumpy w/ 1.6 all around. But when I did the minor rebuild now it is pretty smooth?? Made me wonder if some of it was slop in the worn stock timing chain and weak butt stock valve springs?? :confused:
Le Mans Master
Joined: Feb 2000
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From: Kempner Texas
Re: WHY SPLIT ROLLER ROCKER RATIOS? (redcorvettedave)
------------------------------------------------------------------------
On the LT1s, the intakes are on the left. :lol: :lol: :lol:
________________________________________ ___________
:conehead is the driverside the left!!! :hat :conehead :jester
Jake
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Instructor
Joined: Aug 2003
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From: Glendale Az
Re: WHY SPLIT ROLLER ROCKER RATIOS? (redcorvettedave)
OK, I've got my boots on.
In the days before everyone had a dyno available, we would install 1.6 rockers on the intakes in order to fill the cylinder more. The exhaust did not matter as in theory most of the gas was burnt up therefore the volume was not as much as the intake. The whole idea was to make valve springs live.
With todays miracle valve springs, the issue is null and void.
Valve arangement is EIIEEIIE. Have fun. :chevy
In the days before everyone had a dyno available, we would install 1.6 rockers on the intakes in order to fill the cylinder more. The exhaust did not matter as in theory most of the gas was burnt up therefore the volume was not as much as the intake. The whole idea was to make valve springs live.
With todays miracle valve springs, the issue is null and void.
Valve arangement is EIIEEIIE. Have fun. :chevy
Instructor
Joined: Mar 2002
Posts: 239
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From: Fredericksburg VA
Re: WHY SPLIT ROLLER ROCKER RATIOS? (redcorvettedave)
I usually select the exhaust rocker ratio when I am doing the cam design. Changing the exhaust rocker ratio is a means to fine tune the blowdown rate. The number of suitable exhaust lobe series is quite limited, which makes the selection of the exhaust rocker ratio an important part of the overall cam design. One exhaust rocker ratio will give the best power curve for the particular application. Intake rocker ratio is usually limited by durability or other requirements.
