What does changing from a set 1.6 to 1 roller rockers to a set of 1.7 to 1 do for an engine performance wise. I get the general idea of how they would increase the total amount of lift since the cam is "rated" at the 1.6 ratio.... but I would like to know more about this subject. What types of issues must be considered with this type of change? Valve to piston clearence? Can it cause a problem with coil bind? I am going to be using a Lunati hydraulic roller cam with .525" of lift and Edelbrock heads that have springs good for up to .575' of lift. I have another thead on this forum concerning putting better springs on the E-brock heads, would changing to the 1.7 rockers be another reason for new springs? I have Harland Sharp 1.6 rockers now, and was thinking of going with the 1.7 Scorpion rockers if there is some worthwhile performance to be gained.

 

It just like putting a larger cam in the engine. You need the correct springs to go along with the added lift. And yes coil bind can become an issue. You also need to check piston to valve clearance to make sure there are no issues there.

 

Correct. At overlap you're now increasing the amount that the valves are open together, effectively decreasing lobe sep. However the rule of thumb is for increase of .1 in rocker ratio you'll "tighten" the lob sep a degree or so. Not really a big deal. You're also opening the valve farther faster, effectively adding duration.

On the flipside if your heads don't flow well at higher lift than it's a waste of time. Alot of times older heads actually flow worse above say .500 lift. However your Edelbrocks flow better at higher lifts, just as you would expect.

Have you had the cam ground yet? You never got back to me. If not, save your rockers and just have them grind it with higher lift lobes. Or as mentioned, I can have one ground for you as well, possibly saving you money over the Lunati stuff. Just ask Pat (Citcapp). If you're going to stay with the 1.6's or whatever then a good cam grinder can still give you what you what/need by choosing the right lobes and lobe sep.

 

I know in pontiac that if you go from 1.5 to 1.65 you have to open up the head for push rod to move proper do the olds have the meat to do this???

 

I have a brand new set of Scorpion 7/16" stud mount 1.7 ratio Olds rockers. Never been out of the box. When I bought my heads they came with new Harland Sharps.
I'll make you a good deal if you decide to go with the 1.7's

 

how much for the rockers?