increased rocker lift = increased performance??
Thread Starter
Burning Brakes
Joined: Jul 2000
Posts: 1,067
Likes: 2
From: near VIENNA, AUSTRIA
increased rocker lift = increased performance??
wondering if changing out 1.5 steel stamped rockers to eg. 1.6 roller rockers will make a difference.
How much HP gain?
Is increased valve lift always more HP?
How much HP gain?
Is increased valve lift always more HP?
Melting Slicks
Joined: Dec 2000
Posts: 2,041
Likes: 0
From: Wichita, KS
Re: increased rocker lift = increased performance?? (MARKUS_P)
Yes, increasing the rocker ratio will incerase the performance, provided you don't have a meeting of valve and piston. How much performance is dictated by how much cylinder head and cam you have. I've heard that using roller rockers will reduce the oil temps. but I don't have any hard data on that.
Race Director
Joined: Feb 2000
Posts: 12,431
Likes: 1
From: CT
Re: increased rocker lift = increased performance?? (1979toy)
you might see a gain of a few HP. i think 1.6 rockers will increase the lift by .30 :confused: but im not exactly sure. in other words, if you have .450 lift you would then have .480 lift.
Racer
Joined: Aug 1999
Posts: 451
Likes: 2
From: Toronto On
Re: increased rocker lift = increased performance?? (Vetteboy)
The difference in lift is dependant on the lift you have now.
The geometry of the rocker is different, causing the ratio of lift to jump to 1.6 instead of 1.5 .
1.6/1.5 = 1.066666... which means that your existing lift at the valve will be increased by about 7%.
Or, take your cam lift and multiply by 1.6 .
You have to know the existing geometry of your piston, gasket, and head very well to know whether the new lift will crash the valve into the piston.
[Modified by Ace77, 8:34 AM 11/26/2001]
The geometry of the rocker is different, causing the ratio of lift to jump to 1.6 instead of 1.5 .
1.6/1.5 = 1.066666... which means that your existing lift at the valve will be increased by about 7%.
Or, take your cam lift and multiply by 1.6 .
You have to know the existing geometry of your piston, gasket, and head very well to know whether the new lift will crash the valve into the piston.
[Modified by Ace77, 8:34 AM 11/26/2001]
Race Director
Joined: Apr 1999
Posts: 11,520
Likes: 13
From: CORVETTE 77 385 C.I. TEXAS
Re: increased rocker lift = increased performance?? (MARKUS_P)
Between unnoticable to noticeable, maybe about 15. Divide valve lift by ratio normally 1.5 to get cam lift & multiply by new ratio. Stock measure less than 1.5 so 1.52 increases lift. Comp Cams "1.6 were made for tuning."
Melting Slicks
Joined: Oct 1999
Posts: 2,581
Likes: 14
From: Tolar Texas
Re: increased rocker lift = increased performance?? (MARKUS_P)
I've heard of people gaining favorable results by installing 1.5:1 rockers on the intake and using 1:6.1 rockers on the exhaust. Maybe someone could elaborate on this.
Burning Brakes
Joined: Dec 2000
Posts: 1,183
Likes: 2
From: Des Moines Iowa
Re: increased rocker lift = increased performance?? (MARKUS_P)
Before installing more than 1.52 lift rockers, suggest you carefully determine whether you have clearance in the pushrod slot in the head for a 1.6 ratio rocker arm. Many / most times you need to remove heads and use a special tool (I believe it's called a 'louis tool'?) to enlarge this opening to prevent rubbing / interferance of the push rod on the head.
Providing more lift / faster ramp speed of exhaust valves will make the camshaft perform more like newer technology dual pattern camshaft designs. Would probably help some. I recall conversation on this topic in the past, where some engine builders/old timers, suggested improved HP/Performance by using a mix of 1.5 and 1.6, but recall that it was based upon cylinder location, had something to do with length of intake runner and exhaust manifold passages, or something like that.
Providing more lift / faster ramp speed of exhaust valves will make the camshaft perform more like newer technology dual pattern camshaft designs. Would probably help some. I recall conversation on this topic in the past, where some engine builders/old timers, suggested improved HP/Performance by using a mix of 1.5 and 1.6, but recall that it was based upon cylinder location, had something to do with length of intake runner and exhaust manifold passages, or something like that.
Team Owner
Joined: Apr 1999
Posts: 21,953
Likes: 1,445
From: Reno Nevada
2024 C3 of the Year Finalist- Modified
Re: increased rocker lift = increased performance?? (MARKUS_P)
Piston to valve clearance is not a big deal unless you have bigger than 2.055 intakes and more than .550 lift.
I have always ran 1.6 or higher. The Comp Cams roller tips are the way to go on buget performance motors.
The main concern is can your existing spring combo handle increased lift. Not only look at coil bind but retainer to valve stem seal clearance. I had to use .100 longer push rods to get the valve Geometry right with production type heads with screw in studs and guide plates.
I have always ran 1.6 or higher. The Comp Cams roller tips are the way to go on buget performance motors.
The main concern is can your existing spring combo handle increased lift. Not only look at coil bind but retainer to valve stem seal clearance. I had to use .100 longer push rods to get the valve Geometry right with production type heads with screw in studs and guide plates.
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