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Much (any?) advantage to a higher rocker ratio here?
#1321805
10/17/12 01:06 PM
10/17/12 01:06 PM
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Joined: Jan 2003
Posts: 15,439
Val-haul-ass... eventually
BradH
OP
Taking time off to work on my car
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OP
Taking time off to work on my car
Joined: Jan 2003
Posts: 15,439
Val-haul-ass... eventually
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The 452 is going back together w/ ported Victor heads that flow the following:
Lift -- Int / Exh (no tube)
.100 --- 73 / 54
.200 -- 155 / 105
.300 -- 224 / 162
.400 -- 282 / 200
.500 -- 317 / 219
.550 -- 329 / 229
.600 -- 343 / 236
.650 -- 346 / 244
.700 -- 350 / 247
The CR should be 10.8 - 10.9, the converter flash is ~ 4500, peak RPM probably 7000-7200. The cam's a solid roller 265 @ .050", .650" gross (1.5), 108 LSA.
If I bumped up the rocker ratio to 1.6 (either on intake only or both int & exh), it's more like .690" gross. Does this look like a combination that might show benefits w/ the higher ratio, or given the street-driven nature of the car, would the lower ratio help to reduce wear & tear on the valve train?
FWIW #1 - The cam lobes are compatible with the higher ratio and the springs can support the additional lift.
FWIW #2 - I already have complete sets of rockers in both 1.5 and 1.6 ratios, so there's no cost implication (at least in the short term) associated with the ratio decision.
Last edited by BradH; 10/17/12 01:35 PM.
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Re: Much (any?) advantage to a higher rocker ratio here?
[Re: Jeremiah]
#1321807
10/17/12 01:17 PM
10/17/12 01:17 PM
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Joined: Jan 2003
Posts: 684
St. Charles, MO.
Slingshot383
mopar
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mopar
Joined: Jan 2003
Posts: 684
St. Charles, MO.
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Higher ratio rocker lets you run a larger base circle cam and still get the lift you want.
1994 Undercover Chassis 125" altered
stack injected big block, soon blown and injected
Member of The Torque and Recoil Club
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Re: Much (any?) advantage to a higher rocker ratio here?
[Re: Slingshot383]
#1321809
10/17/12 03:53 PM
10/17/12 03:53 PM
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Joined: Mar 2003
Posts: 9,108
Rogue River, OR
Jeremiah
master
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master
Joined: Mar 2003
Posts: 9,108
Rogue River, OR
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Quote:
Higher ratio rocker lets you run a larger base circle cam and still get the lift you want.
Next dumb question: What does a larger base circle do for me? Faster ramp on the cam?
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Re: Much (any?) advantage to a higher rocker ratio here?
[Re: BradH]
#1321810
10/17/12 03:56 PM
10/17/12 03:56 PM
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Joined: Mar 2003
Posts: 9,108
Rogue River, OR
Jeremiah
master
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master
Joined: Mar 2003
Posts: 9,108
Rogue River, OR
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Quote:
Quote:
What is the lash on that cam Brad?
I've seen the same lobe family spec'd anywhere from .018" - .028". I figured I'd start at .024" and go up or down from there depending on how the new combination responds. 
And now for dumb question number 3:
When you spec a cam do you account for lash when deciding on max lift? In example say I have heads that flow 372 at .700 and the cam manufacturer specs .024 lash. Do I want to run a .724ish lift cam?
If I am thread jacking too far off topic feel free to give me the boot.
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Re: Much (any?) advantage to a higher rocker ratio here?
[Re: BradH]
#1321811
10/17/12 04:07 PM
10/17/12 04:07 PM
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Joined: Jun 2003
Posts: 52,972
Romeo MI
MR_P_BODY
Master
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Master
Joined: Jun 2003
Posts: 52,972
Romeo MI
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Faster open rate... plus run more lift than you really need... that way it spends twice the time at that lift (front and back of the lobe).... plus I would only do the intakes... pressure is working on the exhaust side(I never seen added ratio help exhaust unless you were way off) 
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Re: Much (any?) advantage to a higher rocker ratio here?
[Re: Jeremiah]
#1321812
10/17/12 04:07 PM
10/17/12 04:07 PM
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Joined: Jun 2003
Posts: 9,225
Charleston
sixpackgut
Drag Week Mod Champion
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Drag Week Mod Champion
Joined: Jun 2003
Posts: 9,225
Charleston
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oh boy, I had the plessure of spending a hour on the phone with Dewayne a couple weeks ago and spent a half hour on this subject
because i remember everything, I sent you a PM about this subject maybe 5-7 years ago and I remember exactly what you said to me
Last edited by sixpackgut; 10/17/12 04:12 PM.
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Re: Much (any?) advantage to a higher rocker ratio here?
[Re: MR_P_BODY]
#1321813
10/17/12 04:42 PM
10/17/12 04:42 PM
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Joined: Jan 2003
Posts: 15,439
Val-haul-ass... eventually
BradH
OP
Taking time off to work on my car
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OP
Taking time off to work on my car
Joined: Jan 2003
Posts: 15,439
Val-haul-ass... eventually
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Quote:
... I would only do the intakes... I never seen added ratio help exhaust unless you were way off
My thinking / experience, too.
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Re: Much (any?) advantage to a higher rocker ratio here?
[Re: sixpackgut]
#1321814
10/17/12 04:44 PM
10/17/12 04:44 PM
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Joined: Jan 2003
Posts: 15,439
Val-haul-ass... eventually
BradH
OP
Taking time off to work on my car
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OP
Taking time off to work on my car
Joined: Jan 2003
Posts: 15,439
Val-haul-ass... eventually
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Quote:
oh boy, I had the plessure of spending a hour on the phone with Dewayne a couple weeks ago and spent a half hour on this subject
because i remember everything, I sent you a PM about this subject maybe 5-7 years ago and I remember exactly what you said to me
1. I can't remember what I said 5-7 days ago, much less 5-7 years.
2. I do remember his name is spelled "Dwayne" (only one "e").
3. So, what was the result of the conversation w/ him?
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Re: Much (any?) advantage to a higher rocker ratio here?
[Re: Jeremiah]
#1321815
10/17/12 04:52 PM
10/17/12 04:52 PM
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Joined: Jan 2003
Posts: 15,439
Val-haul-ass... eventually
BradH
OP
Taking time off to work on my car
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OP
Taking time off to work on my car
Joined: Jan 2003
Posts: 15,439
Val-haul-ass... eventually
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Quote:
When you spec a cam do you account for lash when deciding on max lift? In example say I have heads that flow 372 at .700 and the cam manufacturer specs .024 lash. Do I want to run a .724ish lift cam?
You also really need to take into account loaded valve train deflection (pushrod & rocker arm flex), actual "as installed" rocker arm ratios, and the like, in addition to lash.
So, yes, you can use the gross lift minus lash as a target value, but what you'll see in the real world w/ all the parts working together can be different still.
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Re: Much (any?) advantage to a higher rocker ratio here?
[Re: Jeremiah]
#1321816
10/17/12 05:22 PM
10/17/12 05:22 PM
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Joined: Jun 2003
Posts: 52,972
Romeo MI
MR_P_BODY
Master
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Master
Joined: Jun 2003
Posts: 52,972
Romeo MI
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Quote:
Quote:
Quote:
What is the lash on that cam Brad?
I've seen the same lobe family spec'd anywhere from .018" - .028". I figured I'd start at .024" and go up or down from there depending on how the new combination responds.
And now for dumb question number 3:
When you spec a cam do you account for lash when deciding on max lift? In example say I have heads that flow 372 at .700 and the cam manufacturer specs .024 lash. Do I want to run a .724ish lift cam?
If I am thread jacking too far off topic feel free to give me the boot.
Actually you would want about .770 lift... like I
said you have max flow at .700 but your only there
once if you go with .724 but if you go with more lift
you will be at it twice
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Re: Much (any?) advantage to a higher rocker ratio here?
[Re: BradH]
#1321820
10/17/12 11:36 PM
10/17/12 11:36 PM
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Joined: Jun 2003
Posts: 9,225
Charleston
sixpackgut
Drag Week Mod Champion
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Drag Week Mod Champion
Joined: Jun 2003
Posts: 9,225
Charleston
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Quote:
Quote:
oh boy, I had the plessure of spending a hour on the phone with Dewayne a couple weeks ago and spent a half hour on this subject
because i remember everything, I sent you a PM about this subject maybe 5-7 years ago and I remember exactly what you said to me
1. I can't remember what I said 5-7 days ago, much less 5-7 years. you said that it was a waste of time. and told me at best I may pick up 6 hp
2. I do remember his name is spelled "Dwayne" (only one "e"). it's a tricky name.
3. So, what was the result of the conversation w/ him? you made a great post about your conversation with Dwayne on rocker ratios. this was back when you bought the victors. about 50 years ago it seems. I wish I would have saved it
Gen 3 power 6.22@110, 9.85@135
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performance only racing, CRT, ultimate converter, superior design concepts, ThumperCarbs
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Re: Much (any?) advantage to a higher rocker ratio here?
[Re: sixpackgut]
#1321822
10/18/12 10:18 AM
10/18/12 10:18 AM
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Joined: Jan 2003
Posts: 15,439
Val-haul-ass... eventually
BradH
OP
Taking time off to work on my car
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OP
Taking time off to work on my car
Joined: Jan 2003
Posts: 15,439
Val-haul-ass... eventually
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Quote:
Brad:  ... 
Dwayne: 
Brad: 
Dwayne: 
Brad: 
Dwayne: 
Yeah, that's pretty much how most of my discussions w/ Dwayne have gone over the years...
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My Duster custom ground Com Cams solid roller cam has BB chevy roller lobes with 1.65 ratio rockers, that combination works very well 
