1.6 rocker arm question
Thread Starter
Burning Brakes
Joined: Jun 2000
Posts: 892
Likes: 0
From: GA
1.6 rocker arm question
Hi all,
Can anyone tell me the gain for using 1.6 roller rockers? Here is the cam spec with 1.5 stock.
Lift:
Intake: .477"
Exhaust: .480"
How much increase will I see with the 1.6 ratio? Also, can any horsepower been seen with this improvement?
Can anyone tell me the gain for using 1.6 roller rockers? Here is the cam spec with 1.5 stock.
Lift:
Intake: .477"
Exhaust: .480"
How much increase will I see with the 1.6 ratio? Also, can any horsepower been seen with this improvement?
Thread Starter
Burning Brakes
Joined: Jun 2000
Posts: 892
Likes: 0
From: GA
Hey Twin... your progress looks great!
I understand the ratio math... but I was reading there were some case were 1.6 ratio will hurt a motor rather than increase horsepower. I don't think my cam is too radical. Actually, I think it is quite mild compared to others in use. My stock engine HP was rated at 350HP. I was wondered how much additional HP I could expect from the 1.6... if any? Not that I would feel a 15HP gain...
NOW TWIN TURBOS... that would be a different feel all together....
I understand the ratio math... but I was reading there were some case were 1.6 ratio will hurt a motor rather than increase horsepower. I don't think my cam is too radical. Actually, I think it is quite mild compared to others in use. My stock engine HP was rated at 350HP. I was wondered how much additional HP I could expect from the 1.6... if any? Not that I would feel a 15HP gain...
NOW TWIN TURBOS... that would be a different feel all together....
Race Director
Joined: Dec 1999
Posts: 16,945
Likes: 9
It really depends on the cam specs but you will probably gain a bit. The ratio math only applies to valve lift specs, if you have love lift specs you simply multiply them by the ratio.
Thanks for the kind words
Thanks for the kind words
Thread Starter
Burning Brakes
Joined: Jun 2000
Posts: 892
Likes: 0
From: GA
Can I hijack my own thread? okay.. cool
Twin... how are you going to put all that power to the pavement? I was thinking about my measly 360 plus Hp and started thinking... WOW TWIN is going to have his hands full... Don't get me wrong.. I am not doubting your project... just in awe
Twin... how are you going to put all that power to the pavement? I was thinking about my measly 360 plus Hp and started thinking... WOW TWIN is going to have his hands full... Don't get me wrong.. I am not doubting your project... just in awe
Race Director
Joined: Dec 1999
Posts: 16,945
Likes: 9
Hoosier Pro Street radials, 29x15,5x16
As for the driveline, 82s came w/ big 1/2 shafts, only problem would be the diff. Montys lived behind his and it will live behind mine, just don't drop the clutch. I'm still looking for a C4 D44, if I find one I will install that and run an additional torque arm like the C4 has.
As for the driveline, 82s came w/ big 1/2 shafts, only problem would be the diff. Montys lived behind his and it will live behind mine, just don't drop the clutch. I'm still looking for a C4 D44, if I find one I will install that and run an additional torque arm like the C4 has.
Thread Starter
Burning Brakes
Joined: Jun 2000
Posts: 892
Likes: 0
From: GA
Hey Twin.. I found my cam specs on Comp Cams webpage. They also did a dyno run on an engine similar to mine. Although my heads may flow a little better than the S/R heads. I also have the 1.6 rollers. I estimated my total lift @.050 to be .508 and .512 respectively. I am thinking my HP might increase over these results and TQ may be down slightly... what do you think?
http://www.compcams.com/Technical/Dy...68H-10_001.asp
http://www.compcams.com/Technical/Dy...68H-10_001.asp
Thread Starter
Burning Brakes
Joined: Jun 2000
Posts: 892
Likes: 0
From: GA
Also.. I found this to check my ratio math....
CAM LIFT vs. GROSS VALVE LIFT
CAM LIFT OR LOBE LIFT X ROCKER RATIO = GROSS VALVE LIFT
THIS LEADS ME TO THE NExT FORMULA TO DETERMINE MY GROSS VALVE LIFT IF I CHANGE MY ROCKER RATIO SUCH AS , INSTALLING 1.6 SBC ROCKERS WITH A COMP. CAMS XTREME ENERGY # XE 268H CAMSHAFT. CURRENT LISTING STATES .477/.480 LI9FT w/1.5 ROCKERS
VALVE LIFT ÷ ROCKER RATIO = LOBE LIFT [ CAM LIFT ]
LOBE LIFT X ROCKER RATIO = GROSS VALVE LIFT
EXAMPLE: .477 ÷ 1.5 = .318 [ LOBE LIFT ]
.318 X 1.6 = .5088 [ GROSS VALVE LIFT ]
NOTE: IF THE CAM HAS A DIFFERENT LIFT FOR THE EXHAUST, USE THE SAME FORMULA FOR THE EXHAUST. ALL OTHER SPEC'S FOR THE CAMSHAFT REMAIN THE SAME.
THEREFORE THE COMP. CAMS #XE 268H USING 1.6 ROCKER RATIO PRODUCES .508/ .512 LIFT
CAM LIFT vs. GROSS VALVE LIFT
CAM LIFT OR LOBE LIFT X ROCKER RATIO = GROSS VALVE LIFT
THIS LEADS ME TO THE NExT FORMULA TO DETERMINE MY GROSS VALVE LIFT IF I CHANGE MY ROCKER RATIO SUCH AS , INSTALLING 1.6 SBC ROCKERS WITH A COMP. CAMS XTREME ENERGY # XE 268H CAMSHAFT. CURRENT LISTING STATES .477/.480 LI9FT w/1.5 ROCKERS
VALVE LIFT ÷ ROCKER RATIO = LOBE LIFT [ CAM LIFT ]
LOBE LIFT X ROCKER RATIO = GROSS VALVE LIFT
EXAMPLE: .477 ÷ 1.5 = .318 [ LOBE LIFT ]
.318 X 1.6 = .5088 [ GROSS VALVE LIFT ]
NOTE: IF THE CAM HAS A DIFFERENT LIFT FOR THE EXHAUST, USE THE SAME FORMULA FOR THE EXHAUST. ALL OTHER SPEC'S FOR THE CAMSHAFT REMAIN THE SAME.
THEREFORE THE COMP. CAMS #XE 268H USING 1.6 ROCKER RATIO PRODUCES .508/ .512 LIFT
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Racer
Joined: Mar 2004
Posts: 292
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From: Plumas Lake CA
Typical gains from a switch to 1.6 RR range from 5 to 20 HP. You're probably looking at 15 to 20, mostly above 3000RPM or so. It pobably won't hurt your bottom end torque much, either. Another benefit of going to full roller rockers is the reduction in heat on top of the head due to the lower friction levels.
Race Director
Joined: Mar 2001
Posts: 11,322
Likes: 1
From: Living in the Hartland
Also need to know if you heads flow better at the new lift height, 1.6 rockers will increase your duration about 2 degrees so you will see some benefits just from that but if the heads flow no better at the new lift height you will see minimul gains.
