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B-1 Originals rocker arm ratio
#1694730
11/05/14 02:04 PM
11/05/14 02:04 PM
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Joined: May 2014
Posts: 503
Idaho
1320Dart
OP
mopar
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OP
mopar
Joined: May 2014
Posts: 503
Idaho
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I’m in uncharted territory (for me) here. Please be nice with regards to my ignorance.  Ok, when it comes to rocker arm ratios, who determines the ratio? I mean is it the rocker arm manufacturer that says “this ratio ### is the best for your head” or does the cam company, or is it the head manufacturer? I see different guys with B-1’s have all sorts of different ratios. Or is it the engine builder themselves that says what ratio to use? I do know that some guys use the different ratios to change their cam specs a bit for fine tuning. But that’s it. I’ve never had to deal with this situation before. I’ve just used what I had and told the cam manufacturer what ratio I was using.
Greg ----------------------------------------------------------------- Cost is irrelevant, making memories is far more valuable! 
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Re: B-1 Originals rocker arm ratio
[Re: 1320Dart]
#1694732
11/05/14 02:24 PM
11/05/14 02:24 PM
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Joined: Apr 2005
Posts: 2,128
Salt Lake City
camastomcat
top fuel
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top fuel
Joined: Apr 2005
Posts: 2,128
Salt Lake City
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Quote:
I’m in uncharted territory (for me) here. Please be nice with regards to my ignorance.
Ok, when it comes to rocker arm ratios, who determines the ratio? I mean is it the rocker arm manufacturer that says “this ratio ### is the best for your head” or does the cam company, or is it the head manufacturer? I see different guys with B-1’s have all sorts of different ratios. Or is it the engine builder themselves that says what ratio to use?
I do know that some guys use the different ratios to change their cam specs a bit for fine tuning. But that’s it.
I’ve never had to deal with this situation before. I’ve just used what I had and told the cam manufacturer what ratio I was using.
IMO It's the manufacturers that come up with the best ratio for the design of the cyl. head. That said, several engine builders have their own ideas to find a tad more power, and it should be left to the smarter folks.
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Re: B-1 Originals rocker arm ratio
[Re: Cab_Burge]
#1694735
11/05/14 02:40 PM
11/05/14 02:40 PM
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Joined: Mar 2006
Posts: 9,910
Eighty Four, PA
B G Racing
master
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master
Joined: Mar 2006
Posts: 9,910
Eighty Four, PA
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Quote:
Changing the rocker ratio affects the engine in two different ways, how far the valves open, how long they stay open and how fast the valves open   I've seen arguments on here from folks that think the duration is not affected by the rocker ratio, evidently they have never charted a cam opening on the same engine with two different ratio rockers 
 It redesigns the cam in both lift and duration as well as power range and etc. 
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Re: B-1 Originals rocker arm ratio
[Re: pittsburghracer]
#1694736
11/05/14 02:40 PM
11/05/14 02:40 PM
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Joined: May 2014
Posts: 503
Idaho
1320Dart
OP
mopar
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OP
mopar
Joined: May 2014
Posts: 503
Idaho
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I've seen 1.6 to 1.83 for ratios on just the B-1's
What brand is preferred with the B-1's?
I planned on T&D paired rockers. But before I pulled the trigger I was wondering about the rocker ratio and had to ask.
Greg ----------------------------------------------------------------- Cost is irrelevant, making memories is far more valuable!
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Re: B-1 Originals rocker arm ratio
[Re: dogdays]
#1694739
11/05/14 02:50 PM
11/05/14 02:50 PM
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Joined: May 2014
Posts: 503
Idaho
1320Dart
OP
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OP
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Idaho
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Quote:
A lot depends on the camshaft, as well. I'd start there.
R.
Can you elaborate a little more please?
Greg ----------------------------------------------------------------- Cost is irrelevant, making memories is far more valuable!
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Re: B-1 Originals rocker arm ratio
[Re: B G Racing]
#1694740
11/05/14 02:55 PM
11/05/14 02:55 PM
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Joined: Dec 2013
Posts: 403
Romulus, MI
GTS340
mopar
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mopar
Joined: Dec 2013
Posts: 403
Romulus, MI
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Quote:
Quote:
Changing the rocker ratio affects the engine in two different ways, how far the valves open, how long they stay open and how fast the valves open I've seen arguments on here from folks that think the duration is not affected by the rocker ratio, evidently they have never charted a cam opening on the same engine with two different ratio rockers
It redesigns the cam in both lift and duration as well as power range and etc.
I'm having trouble following this, duration numbers are specified in regards to tappet lift at the lobe correct? Wouldn't changing rocker ratio only affect lift at the valve in regards to lobe lift? Sure it will affect the rate of lift at the valve just as a result of the changed ratio, I just don't see how the ratio change could physically change the the profile ground on the lobe which sets duration
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Re: B-1 Originals rocker arm ratio
[Re: Monte_Smith]
#1694743
11/05/14 03:55 PM
11/05/14 03:55 PM
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Joined: May 2014
Posts: 503
Idaho
1320Dart
OP
mopar
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OP
mopar
Joined: May 2014
Posts: 503
Idaho
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Quote:
Camshafts are limited by the available blanks and the lobes those blanks have and actually how big a lobe can physically fit in the cam tunnel. So most consider a .500 lobe a big lobe, yet when coupled with a 1.5 rocker, that only gives .750 lift......that's pretty damn small. So say you want .900 lift and have a 1.5 rocker. That would require a .600 lobe. Ain't gonna happen, no such thing on a stock journal size blank. Now that same .500 lobe mentioned before, when put with a 1.8 rocker, gives you .900 lift.
Monte
Hi Monte-
Does that change much if a person was to run a 54mm cam? Or does that just help keep the core diameter bigger?
Greg ----------------------------------------------------------------- Cost is irrelevant, making memories is far more valuable!
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Re: B-1 Originals rocker arm ratio
[Re: GTS340]
#1694744
11/05/14 04:46 PM
11/05/14 04:46 PM
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Joined: Mar 2006
Posts: 9,910
Eighty Four, PA
B G Racing
master
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master
Joined: Mar 2006
Posts: 9,910
Eighty Four, PA
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Quote:
Quote:
Quote:
Changing the rocker ratio affects the engine in two different ways, how far the valves open, how long they stay open and how fast the valves open I've seen arguments on here from folks that think the duration is not affected by the rocker ratio, evidently they have never charted a cam opening on the same engine with two different ratio rockers
It redesigns the cam in both lift and duration as well as power range and etc.
I'm having trouble following this, duration numbers are specified in regards to tappet lift at the lobe correct? Wouldn't changing rocker ratio only affect lift at the valve in regards to lobe lift? Sure it will affect the rate of lift at the valve just as a result of the changed ratio, I just don't see how the ratio change could physically change the the profile ground on the lobe which sets duration
Draw the existing lobe as designed with the designated rocker ratio ie:1.5 ratio,then super impose the same lobe with 1.7 ratio rocker movement and follow the cycle from where the movement starts at the ramp to max lift as well as dwell time.It will travel well outside of the original cam demension.As Monte explained about cam core/lobe size your limited to certain dementions for clearence and geometry design.Big lobes sometimes will interfere with rods especially with large strokes and valve train geometry.This is why you see raised cams,spread bores and lifter cup height.The big journal cam cores are to strengthen the shaft and minimize flexing.Large lobes with steep ramps create problems keeping the lifter in contact and bouncing at high rpms which is why we have to use ultra heavy spring pressure and ultra expensive componants.
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Re: B-1 Originals rocker arm ratio
[Re: B G Racing]
#1694745
11/05/14 05:11 PM
11/05/14 05:11 PM
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Joined: Dec 2013
Posts: 403
Romulus, MI
GTS340
mopar
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mopar
Joined: Dec 2013
Posts: 403
Romulus, MI
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Quote:
Draw the existing lobe as designed with the designated rocker ratio ie:1.5 ratio,then super impose the same lobe with 1.7 ratio rocker movement and follow the cycle from where the movement starts at the ramp to max lift as well as dwell time.It will travel well outside of the original cam demension.
Taking measurements from the same give point ie: .050 valve lift? Or as soon as indicator starts to move?
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Re: B-1 Originals rocker arm ratio
[Re: B G Racing]
#1694747
11/05/14 05:33 PM
11/05/14 05:33 PM
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Joined: Dec 2013
Posts: 403
Romulus, MI
GTS340
mopar
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mopar
Joined: Dec 2013
Posts: 403
Romulus, MI
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Quote:
Measure it from any point after bottom base circle,.020,.050.
There will definitely be a change of valve rate of lift due to rocker ratio. The duration @ .050 on the cam hasn't changed, just the rate of lift at the valve and amount the valve is opened IE: .075 with 1.5 ratio and .085 with 1.7, is this really considered a change in duration? If so do you also consider it a duration change when you change roller lifters from one size roller wheel to another?
I was taught duration is at the lobe only
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