Rocker arm ratio

[cheapcharlie]

I have a s/b chevy with a solid flat lifter cam.This cam is semetrical with .580 lift and 275 deg dur @.050 seat dur is 320. this is with 1.5 rocker ratio.I also have 8 1.6 ratio rockers I was thinking of trying.the ratio change won,t change the opening or closing points but should give a small increase in effective duration.This cam has 110 lobe centers and is ground 2deg. advanced. Its installed split overlap at 108 atdc.Everyone I,ve asked says to put them on the intakes but I was thinking maybe try em on the ex side.This probably is not enough info but would like some opinions.Coil bind and valve clearance are not issues. Thanks in advance.

 

[MikeHalloran]

Popular lore says you'll always get more power from the longer rockers, but there may be other choke points and side effects.

You might also consider running Rotella T instead of regular motor oil. Here's why:

http://www.ericpetersautos.com/home/index.php?option=com_content&task=view&id=300&Itemid=10816

... it was a surprise to me.



Mike Halloran
Pembroke Pines, FL, USA

 

[MikeHalloran]

... and a little followup from the other side:

http://www.mobiloil.com/USA-English/MotorOil/Car_Care/AskMobil/Synthetic_Oil_and_Tappets.aspx

Mike Halloran
Pembroke Pines, FL, USA

 

[SMOKEY44211]

There have been a number of articles published on dyno tests sbc indicating that there is little if anything to be gained by increasing exhaust valve lift. (via higher rocker ratio) Most reports indicate there is something to be gained by higher lift on the intake side. The intake closing event has the most influence on the engine torque curve. I would echo Mike's advice regarding the use of rotella oil, especially for break in period. I've seen a number of flat tappet lobe failures without its use. Another point of failure is the distributor driven and drive gear.-------Phil