1.5 vs 1.6 rocker arms
06-05-2005, 07:36 PM
#1
Team Owner
Thread Starter
1.5 vs 1.6 rocker arms
My apologies if this has been expounded upon in other posts...the search function doesn't turn up anything, so I'm starting a thread.
How much more lift does one gain (mathematically) when one switches from 1.5 to 1.6 rocker arms? If I know my lift on my current set-up, basically I want to calculate what it would be with different rockers, and figure out what the clearance is.
A second question, are there any drawbacks from going to 1.6 rockers?
I haven't started anything yet, just curious.
TIA,
trw
How much more lift does one gain (mathematically) when one switches from 1.5 to 1.6 rocker arms? If I know my lift on my current set-up, basically I want to calculate what it would be with different rockers, and figure out what the clearance is.
A second question, are there any drawbacks from going to 1.6 rockers?
I haven't started anything yet, just curious.
TIA,
trw
06-05-2005, 08:40 PM
#2
Le Mans Master
Member Since: Apr 2000
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St. Jude Donor '09
Rocker ratio x lobe lift. If your lift at the valve is .480 with 1.5 rockers for example, the lobe lift is .320. So your final lift would be lobe lift x rocker ratio.
Drawback is higher stress on the valve train.
Drawback is higher stress on the valve train.
Last edited by yellow 72; 06-05-2005 at 08:43 PM.
06-05-2005, 08:45 PM
#3
Le Mans Master
valve lift divided by 1.5 will give you cam lift. Then multiply cam lift times 1.6 and get the new valve lift.
The first issue you run into with stock heads is the pushrod holes. On stock heads you could have interfearance with the pushrod slots when converting to higher ratio rocker arms on stock heads. The pushrod moves closer to the pivot point so that is where the extra ratio comes from. This will also increase the load seen by the valvetrain. You will loose some small amount of RPM potential, The valve lash will be about .0015" bigger for the same solid lifter cam and you need to watch out for the retainers bottoming out on the top of the valve guide. The seat to seat timing is unchanged. A small change in power might happen when comparing to the same type of rocker arm in the original ratio but you would need to experiment to find out if you need them on the intake, the exhaust, or both.
Decide for yourself.
-Mark.
The first issue you run into with stock heads is the pushrod holes. On stock heads you could have interfearance with the pushrod slots when converting to higher ratio rocker arms on stock heads. The pushrod moves closer to the pivot point so that is where the extra ratio comes from. This will also increase the load seen by the valvetrain. You will loose some small amount of RPM potential, The valve lash will be about .0015" bigger for the same solid lifter cam and you need to watch out for the retainers bottoming out on the top of the valve guide. The seat to seat timing is unchanged. A small change in power might happen when comparing to the same type of rocker arm in the original ratio but you would need to experiment to find out if you need them on the intake, the exhaust, or both.
Decide for yourself.
-Mark.
Last edited by stingr69; 06-05-2005 at 09:06 PM.
06-05-2005, 09:12 PM
#4
Melting Slicks
Member Since: Jan 2004
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Originally Posted by stingr69
The first issue you run into with stock heads is the pushrod holes. On stock heads you could have interfearance with the pushrod slots when converting to higher ratio rocker arms on stock heads.
06-05-2005, 09:22 PM
#5
Drifting
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You would have around .512 lift with 1.6 rockers. This is a significant difference imho. The problem with more lift is you need intake & exhaust to take advantage of it.
06-06-2005, 04:41 PM
#6
Team Owner
Thread Starter
Thanks again for the info...I was asking cause one of my C5 buddies this weekend was giving me guff for not running 1.6 rockers, and i was trying to decide if that was something I should or wanted to do.
I've got exhaust to do first before I tackle rocker ratio.
I've got exhaust to do first before I tackle rocker ratio.
