I got a set of roller rockers, and it turns out that 8 are 1.5 and 8 are 1.6 ratio, I asked and was told to put the 1.6 on the exhaust and 1.5 on the intake side. Well as far as I remember , it is harder to vacuum in a fresh air/fuel mixture into the chamber than it is to scavenge out the spent g***es, so I was thinking shouldn't the 1.6 rockers be put on the intake side to open up the valve more and longer, to let more charge come in, and put the 1.5 on the exhaust side since spent g***es exit out faster???? Also when I was looking to get an ignition coil, (an aftermarket high voltage style) there are about 6 different ohm. ratings for them all, .04/.05/.06/.07 etc. How do I know which one to pick?? Engine is a SBC 350, with rv cam, flat tops and camel humps, the distributor, is an older mallory dual point, the style with a 2 piece cap , and the huge condensors mounted on the outside of the distributor housing. The coils were...Accell super coil, MSD blaster, and pertronics. Then this brings up the ballast resistor, the original coil wire was a ballast wire from the factory. How do I know which ballast resistor to get??
It's about lift and duration. The ex valves are also smaller so a little more lift can't hurt. Figure the lift on the cam with each rocker ratio. The cam card will tell how it was figured, 1.6 or 1.5. I.E., a cam lobe lift of .300 would be .450 with a 1.5 or .480 with a 1.6. Hangin the ex vale open just a tad more helps to bring fresh charge into the cylinder as well. What you're thinking would be near correct if all things were created equal within the dynamics of the head design...they're not. As far as the coil, do a bit of research as to the OEM coil spec. Squirrel here may have that tidbit of info. The Accell is probably the safest choice for a direct hook up to existing circuitry.
Dual pattern cams for small block Chevs have higher lift on the exhaust side because it is less efficient than the intake side. You can achieve the same effect by using the 1.6 rockers on the exhaust side. Better check the specs of the cam you have though in case you already have a dual pattern cam or a lot of lift. MSD, Pertronics possibly Accel and Jegs and Summit can tell you what ballast resistor to use, if any.
I can tell ya when we set up my 350 I was told by many engine builders to use the stainless roller rockers and get 1.5 for intake, and 1.6 for exhaust and it runs like a champ. Being a flathead guy I didn't have much experience on small blocks, so I ask several builders and came up with the same answer.--TV
Also keep in mind intake valves are bigger and using the 1.6 rockers may increase chances of the piston meeting the valve just enough to ruin your day. Scott
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